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Antarctic CRC Research Report 14 - Antarctic Sea Ice Processes

1. e OC E ON NE uM a XE UE NES 5 A 6 3e 5 o a Ice thickness category b Snow thickness category m Figure 4 2 Monthly ice and snow thickness distributions determined from all available ship based sea ice observations The discussion of Figures 4 2 a and b focuses on the months of March August October and December In March there is approximately 25 open water and an additional 60 of ice less than 0 4 m indicative of rapid new ice growth over large areas of the Southern Ocean Most of this ice has a thin snow cover with less than 1096 greater than 0 1 m In August the pack is quite consolidated and the open water fraction averages only 12 There is only a small percentage of ice less than 0 4 m thick due to cold air temperatures at this time of year quickly refreezing leads to greater than 0 4 m and also due to the effects of deformation This is supported by observations in the winter pack showing that ice may quickly grow to more than 0 4 m Worby et al 1996a Hence only a small fraction of the pack is comprised of open water and thin ice the opposite of the March distribution but the snow cover is predominantly less than 0 2 m By October two changes in the ice growth regime contribute to the flattening of the thickness distribution curve First leads do not r
2. 7 Fl OF DISE FOIL rl 2098 509 gg v A ge pou co ______ _____ Cl eg v o pe Mayr 7 erg ooi cos 45 e 71 0 14 ccv 96 9 4 500 727 eos cb pers mu Se up v cay ve go muy 10 7 SCIL yw s sem cO 90 UL X wg es 12 98 8044 Wu gos arg H cvs 55 eL g 999 p 76 sp e e ses 58 SR 3 eng g b a JUNE ______ _ _ fl FF yf ems o mg o ow oL GF Ber gTr E SO 20 reo ne cg n b bE s9 8 I eer ep 2196 97 95 BEA E log oR og SI sod E og eh 2259 LL E 7 7 78 1 1 7 2 78 8 5 pp 7 SNOLLV HOI VAS 2 21 2 8 8 3 LER X ecl 6 38 gt ton Petra Rob OBSERVER a 2 no Ref COMMENTS 4 a N 3 5 5 ofS 3 9
3. for snow thickness 300 cm total ice sum pri sec ter Icheck pri gt sec gt ter thickness snow thickness gt ice thickness thick corresponds to ice type thick IISPECIFIC ICE TYPE CHECKING list of ice type checks below ICE CONCENTRATION CHECKS I see list of total conc open water checks 55 Coefficients record struct COEFFRECORD BOOL isValid 10 4 double 1014 char comments 100 har 50 Factory Default coefficients values static double COEFF FACTORY COEFF 12 3 0 07 0 09 0 17 0 24 0 21 0 32 0 70 0 21 0 32 0 70 0 35 0 50 0 74 0 50 0 65 0 77 0 60 0 74 0 85 0 60 0 74 0 85 0 60 0 74 0 85 0 55 0 55 0 55 0 60 0 74 0 85 Convert to text file record struct TEXTRECORD srcFile 80 the name of the source database file char desF ile 80 the name of the destination text file BOOL entireF ile I TRUE if entire file is to be converted short int selectedMonth currently selected month 1 12 BOOL selectedDays 31 Icurrently selected days to convert BOOL fields TEXTFIELDS of the fields below to convert Y 3 4 Check and Validation Rules As described in section 2 6 1 the Input Validation Control dialog box can be used to enable or disable various validation checks that are performed on the data when a new observation record is entered If enabl
4. gt Cloud Visib Weath 0 1 uu 1995 422 METEOROLOGICAL OBSERVATIONS 1 67 0 6 02 1 5 25 gt e O z i Y Lj c 2 gt O ui lt 2 gt O a lt gt gt lt gt 2 gt gt 4 lt Z Q lt aE e 1 3 3 1 0 4 3jozo 8 43 78 TH AL 3 H MIS 8 id wd N Q 33445 E 2 8 gt 2 NOTES 22 7am 5 7 you TOLG AI UD DAS AMAA 3 4 agn vedo ay Evry PART Il USER OPERATING MANUAL FOR SOFTWARE 24 1 0 INTRODUCTION 1 1 General Description This program seaice exe facilitates the digitising quality control and processing of ship based observations of Antarctic sea ice characteristics It is designed for use in conjunction with but not to replace the handwritten sea ice observation log sheets The program allows the user to supply and verify all observation data via a dialog box user interface The advantages of this are The data are entered and quality controlled during the voyage All data quality checking is performed at the time the data are entered enabling any errors or ambiguiti
5. 65 150 7 5 aug 1997 02 00 65 150 140 083 10 0 1 9 140 007 10 0 137 140 583 10 0 17 8 140 567 100 216 10 140 550 10 0 237 10 140 500 10 0 520 9 140 317 100 433 2 Abbreviations used the text file listing Lat Latitude OW Open water Conc Long Longitude Ice concentration Track Distance of observation along ship s route from first observation of voyage Primary Ice Secondary Ice cl primary ice conc C2 Secondary ice conc tyl primary ice type ty2 secondary ice type 21 primary ice thickness 22 secondary ice thickness fl primary floe size f2 secondary floe size tl topography 0 secondary topography sl primary snow type S2 secondary snow type 521 primary snow thickness 522 secondary snow thickness 29 il tl 51 571 60 30 800 100 3 7 60 50 700 502 3 10 60 65 800 702 3 10 65 800 713 3 15 60 800 713 3 10 70 800 13 3 20 75 800 711 4 15 Tertiary Ice C3 tertiary ice conc ty3 tertiary ice type iz3 tertiary ice thickness f3 tertiary floe size t3 tertiary topography S3 tertiary snow type 523 tertiary snow thickness Meteorological SeaT Sea temperature in degrees C Air T Air temperature in degrees C W Vel Wind velocity in m sec W Dir Wind direction in degrees 0 359 Film Film counter Frame Frame counter for the film Video Video recorder counter hh mm ss Visib Visibility code Cloud Cloud in oktas Weath Weather code 2 2 3 Import Old Database F
6. gt Ter Ice Thickness Ice thickness gt Snow Thickness Warning Only Ice Thickness Corresponds to Ice type thickness YES Ice Type Checks YES H0 WARH Checks That Frazil Shuga Grease ize 200 400 500 600 700 100 500 600 700 1 2 3 4 10 15 to 30 Snow Thick lt 20 cm ist Year Ice 30 70 15 Year Ice 70 120cm open water open water open water open water open water open water Figure 2 21 Input Validation Dialog Box 47 To calculate the area averaged albedo from the observed sea ice types and thicknesses a table of albedo coefficients is specified The coefficients can be displayed and changed Refer to section 2 6 2 or All the validation checks described in detail Appendix They also described briefly here To change the Setting between YES NO and WARNING ONLY for a particular parameter simply click on the line containing the validation rule To change the validation check settings for all the parameters in General Checks Ice Type Checks or Total Concentration Checks click on the All YES All NO or All WARNING ONLY buttons General Checks e Ice Thickness lt 2000 cm The ice thickness must be less than 2000 cm e Snow Thickness lt 300 cm The snow thickness must be less than 300 cm e Total Ice Conc Sum Pri Sec Ter The total ice concentration must equal the sum of individual ice concentrations When no tertiary ice is specified sumzpri4sec When no se
7. updating the new log file Select highlight one of the records in the list box on the left and then click this button The record is edited in the Same way as described in section 3 2 Note that the original data base text file is not affected only the data in the list box is changed A record can be removed from the list of records in the left list box by first highlighting the record and then pressing this button The program will prompt to confirm before deleting the record The old data base is not affected This drop list box is used to specify the records from the old database fin file that are to be added to the new log file There are three options i Add All Records No Confirm Each record from the fin file is added to the log file without ii Add All Records Confirm iii Add Valid Records Only e Round off to Hour confirmation The user is asked to confirm each record before adding it to the log file Some records from the old database fin file may not be valid hence these records may not be added if this is chosen This check box is used to round off the time from the imported files to the nearest hour The time is stored as a decimal fraction in the form ddd dd i e ddd day and dd fraction of day hence when converting 31 back to hours minutes the minutes will be rounded off i e the times 11 58 and 12 01 will be rounded off to 12 00 Log Database File This is the output file with the extensi
8. AND PROCESSING Software has been written to enable the ship based observations to be entered and processed on a PC A comprehensive user operating manual for this software is presented in Part Il of this report A summary of the main features is presented below 3 1 Quality control Checks are made to identify errors and inconsistencies in the data These include but are not limited to snow thicker than ice thin ice types greater than 0 1 m thick total concentration greater than 10 10 or not adding up to the sum of the concentrations of the three dominant categories e thickness categories not matching assigned thickness values topography or floe size codes incompatible with ice type 0 consolidated ridges on nilas primary ice category thinner than secondary or tertiary categories e distance between consecutive hourly observations greater than 20 km The program checks the data for each hourly entry and prompts the user when erroneous or anomalous data are entered When entries are clearly wrong the quality control software will insist that the correct data be entered and will not accept the record until corrections are made In cases when the data appear to be wrong but in fact represent unusual ice conditions e g unusually thick snow on thin nilas the quality control software will accept the entry after it has been flagged and checked See Partll Sections 2 6 and 3 4 for more details on data quality contr
9. Polar Research Institute 1973 Australian Bureau of Meteorology Recording and encoding weather observations Publication B 220 Catalogue No 216610 38 pp 10 Bush G A J Duncan D Penrose and Allison Acoustic reflectivity of Antarctic sea ice at 300 kHz in Proceedings of the 3rd European conference on underwater acoustics pp 883 888 Heraklion Crete Greece 1996 Buynitskiy V K Structure principal properties and strength of Antarctic sea ice Sov Antarct Exped Inform Bull 65 504 510 1967 Comiso Grenfell Bell Lange and 5 Ackley Passive microwave observations of winter Weddell Sea ice J Geophys Res 95 8 10 891 10 905 1989 Comiso C and H J Zwally Concentration gradients and growth decay characteristics of the seasonal sea ice cover J Geophys Res 89 C5 8081 8103 1984 Eicken A Lange H W Hubberten and Wadhams Characteristics and distribution patterns of snow and meteoric ice in the Weddell Sea and their contribution to the mass balance of sea ice Ann Geophys 12 1 80 93 1994 Haas C Evaluation of ship based electromagnetic inductive thickness measurements of summer sea ice in the Bellingshausen and Amundsen Seas Antarctica Cold Regions Sci Technol 27 1 16 1998 Gloersen P and D J Cavalieri Reduction of weather effects in the calculation of sea ice concentration from microwave radiances J Geophys Res 91 C3 391
10. Technol 5 1 12 1981 Wadhams M A Lange and 5 Ackley The ice thickness distribution across the Atlantic sector of the Antarctic Ocean in midwinter J Geophys Res 92 C13 14 535 14 552 1987 WMO World Meteorological Organisation Sea Ice Nomenclature Terminology Codes and Illustrated Glossary WMO OMM BMO 259 TP 145 World Meteorological Organisation Geneva Switzerland 1970 Worby A P Seasonal variations in the thickness distribution and snow cover of Antarctic sea ice in the region 60 150 E PhD thesis 195 pp University of Tasmania Hobart Tasmania Australia 1998 Worby A P Observing Antarctic Sea Ice A practical guide for conducting sea ice observations from vessels operating in the Antarctic pack ice A CD ROM produced for the Antarctic Sea Ice Processes and Climate AS P eCt program of the Scientific Committee for Antarctic Research SCAR Global Change and the Antarctic GLOCHANT program Hobart Australia 1999 Worby A P and Allison Ocean atmosphere energy exchange over thin variable concentration Antarctic pack ice Ann Glaciol 15 184 190 1991 11 Worby A P Bindoff V I Lytle Allison and A Massom Winter sea ice ocean interactions studied in the East Antarctic EOS Trans AGU 77 46 453 456 457 1996a Worby A P Griffen V Lytle and A Massom On the use of electromagnetic induction sounding to determine winter and spring sea i
11. and the program will display the daily records for that particular day To the right of the day list box the year s is listed The database may Span more than one year e g Nov 97 J an 98 hence the appropriate year must be selected To change the size of the font used to list the data on the main screen simply choose a different font The font size box is located just below the year list box This menu function allows the user to open an existing observation log file or to create a new observation log file From the File menu choose the Open Observation Log option The file browser dialog box Figure 2 2 appears on the screen Open File name test12 log List files of type Files log Folders c albedo Cancel c amp albedo dii Network Figure 2 2 Open Observation Log Dialog Box All log file names must have the extension 400 f the log file exists it will be loaded and the contents displayed on screen If the file does not exist an empty file will be created The daily records of the first day containing data are displayed The log file name will appear on the top left corner of the main window the month list box will display the number of records for each month and the day list box will display the number of records for each day of that particular month By clicking on the day list box you can display the records for the particular day that is selected To view specifi
12. discernible visibility 1000 Fog depositing rime sky discernible visibility lt 1000 m Fog depositing rime sky not discernible visibility 1000 3 6 5 Precipitation As Drizzle 50 59 Slight drizzle intermittent Slight drizzle continuous Moderate drizzle intermittent Moderate drizzle continuous Dense drizzle intermittent Dense drizzle continuous Freezing drizzle slight Freezing drizzle moderate or dense Drizzle and rain slight 60 59 Drizzle and rain moderate or dense 3 6 6 Precipitation As Rain Not Showers 60 69 Slight rain intermittent Slight rain continuous Moderate rain intermittent Moderate rain continuous Heavy rain intermittent Heavy rain continuous Freezing rain slight Freezing rain moderate or heavy Rain drizzle and snow slight Rain or drizzle and snow moderate heavy 3 6 7 Frozen Precipitation Not Showers 70 79 Slight fall of snow flakes intermittent Slight fall of snow flakes continuous Moderate fall of snow flakes intermittent Moderate fall of snow flakes continuous Heavy fall of snow flakes intermittent Heavy fall of snow flakes continuous Ice prisms with without fog Snow grains with without fog Isolated starlike snow crystals Ice pellets 3 6 8 Precipitation As Showers 80 90 ight rain showers oderate or heavy rain showers olent rain showers ight showers of rain and snow oderate heavy showers of rain and snow ight snow showe
13. down combo box allows the file name of either the met or ice database files old format to be specified it has five different selections as shown below Once the file is imported the file name is displayed and the contents are listed in the list box below the file name This is a read only edit box i Import V1 X Albedo FIN Ice File The database file is an old V1 X ice obs of the seaice ii Import V1 X Albedo iii Import Unix FI3 Ice file windows program preceding this version created by Dirita Met File database file is an old V1 X met obs of the seaice windows program preceding this version created by Dirita The database file contains ice obs and was created via the unix version of the program by A Worby iv Import Unix OLD Met 1986 1991 The database file contains met obs and was created via the unix version of the program by A Worby v Import Unix OLD Met 1992 1995 The database file contains met obs and was created via Met View Edit Record e Remove Record Selection the unix version of the program by A Worby This box contains the file name of the ice obs data which has been loaded using the import button above This is a read only edit box This box contains the file name of the met obs data which has been loaded using the import button above This is a read only edit box You can manually edit individual records in the old database file before
14. induction techniques Haas 1998 Worby et al in press satellite remote sensing e g Comiso and Zwally 1984 Gloersen and Cavalieri 1986 and ship based observations e g Worby et al 1996b Worby et al 1998 Each of these observational techniques has acknowledged biases and therefore different techniques are useful for identifying different thickness categories within the pack ice Worby 1998 The ship based observations are particularly useful for providing localised information on sea ice thickness and characteristics which over the duration of a voyage amount to semi synoptic coverage of the pack The ship based observations also discriminate thin sea ice types which are not represented in the drilled thickness data and are problematic for the interpretation of S SM I data from satellites Corniso et al 1989 One of the problems faced by observers making ship based observations of sea ice thickness and other ice characteristics has been the lack of a standardised system for making and recording the observations Observations of e g Sea ice type concentration thickness and surface topography have been maintained on many voyages over the past two decades however these have often been in the form of written notes and in many instances there has been no quantitative analysis of the data Furthermore individual data sets are rarely in a format comparable with others from different voyages making regional or seasonal comparisons i
15. lif the ice classification is valid short int iceConc lithe ice concentration 0 10 short int lice type code Short int floeSize size code Short int topography code Short int snowType Isnow type code float iceThick Ilice thickness in cm float snowThick 1 5 thickness in cm Y Single Ice observation struct ICERECORD BOOL isValid llif the observation was made TIMEDATE Tobs time and date when the observation was made float lat latitude in degrees float on longitude in degrees float distTrack I distance since start of log first observation float distE dge distance from the edge of ice short int totallce ice concentration short int openWater lopen water code char comments 120 comments field ICEOBS pri sea ice data ICEOBS Sec sea ice data ICEOBS ter tertiary sea ice data char 50 I spare fields for future use Y 54 Single Met observation struct METRECORD BOOL isValid TIMEDATE Tobs float at float on float seaTemp BOOL isValidSeaT emp float airTemp BOOL isValidAirTemp Short in windVel BOOL isValidWindVel short in windDir BOOL isValidWindDir Short in photoF ilm BOOL isValidP hotoF ilm Short in photoF rame BOOL isValidP hotoF rame Short in video BOOL isValidVideo Short in visibility Short in cloud Short in weatherCode
16. not be specified 49 2 6 3 Observation Record Defaults From the Options menu select the Observation Record Defaults option This menu function is used to initialise the observation record with some default values The dialog box shown in Figure 2 23 appears on the screen Use The Previous Lat Lon Entry Leave Lat Lon Fields Empty Lat N S Lon E W Lat Lon Input Format Defaults For Observation Record Figure 2 23 Observation Record Defaults When a new record is being added to the log file the latitude and longitude fields will be shown as that of the previous record entry if this box is checked When a new record is being added to the log file the latitude and longitude fields will be blank if this box is checked This is used to set the hemisphere default for latitude to either north or south ifthe Leave Lat Lon Fields Empty check box is selected This is used to set the hemisphere default for longitude to either east or westifthe Leave Lat Lon Fields Empty check box is selected The default latitude and longitude may be specified as either decimal degrees or degrees and minutes The default setting applies to all aspects of the program including data entry plotting and display The default setting may be changed at any time 50 Sea Temperature No Wind Speed No Wind Direction No Photo Film No No Photo Frame No No Video Counter Check this box to set the de
17. pes 915902 9 005 lt SXea1q KI9A 005 005 SILA PIM 02 06 55914 uc Sxvo1q moreu SOLI ssulusdo ON NHdO 13111586 MOUS se ppnd Ysnys 9W 7 MOUS PIO MOUS MOU MOUS MON mous MOUS plo gt MOUS MOU 18014 IO MOUS ON 9540 MOUS ON S MONS wos Uu ye Uu c gi 148194 res Ae G 0 Sen eA 001 06 06 08 08 OL 01 09 09 06 05 07 0 0 0 lt 0 0C OT 8 01 0 5 x sb IPJO 8 8 ou SOSPLI MOUS IO MOUS MOUS ou 8 1 8 4 OOP soyeourd 006 soxeoued poyey 00 001 4 AHdV3I2OdOL 0005 lt 590 008 000 005 soo 00L 006 001 saoz 009 01 0 5204 006 Qc exe 007 oor uoxoiq gserq 00 oor 1994 MON 00 soxeoueq 001 D AZIS so1jouinuoo ur oq ZS MONS NV 2 AOI VAS ur 01 2 uyONOO AOI 991 15
18. polar stereographic coordinates Track distance calculations 3 8 1 Latitude distance 3 8 2 Longitude distance 3 8 3 Track distance PART OBSERVATIONAL TECHNIQUE AND RESULTS 1 0 INTRODUCTION The sea ice thickness distribution is a fundamental parameter for defining the extent of ocean atmosphere interaction within the sea ice zone as well as the extent of mechanical deformation within the ice field Combined with sea ice extent it also defines the total ice volume and possible response of sea ice to climatic change combined with ice velocity it defines the mass flux of ice and combined with the multi year ice fraction ice structural composition and ice temperature and Salinity it defines the mechanical strength of the ice cover However sea ice thickness is one of the most difficult geophysical parameters to measure over large spatial and temporal scales It can not be measured remotely hence the need for in situ measurements to determine the distribution and thickness of different ice types within the pack ice zone In the Antarctic over the past several decades numerous field investigations have employed different techniques for measuring sea ice thickness These include drilled measurements Ackley 1979 Allison and Worby 1994 Eicken et al 1994 Jeffries and Weeks 1992 Lange 1991 Wadhams et al 1987 upward looking sonar Bush et al 1996 Strass and Fahrbach 1998 impulse radar Wadhams et al 1987 electromagnetic
19. range is ignored If this box is not checked then the user must specify a subset of records to be processed defined by a range of latitude This is used to specify a subset of the data file by latitude All observations outside this range will not be processed You may specify the From and To values in any order i e From 60 S to 6595 will produce the same result as From 6595 to 6095 The specified range can not be greater than 90 degrees If this box is checked then the longitude range is ignored If this box is not checked then the user must specify a subset of records to be processed defined by a range of longitude This is used to specify a subset of the data file by longitude All observations outside this range will not be processed You may specify the From and To values in any order i e From 170 E to 165 W will produce the same result as From 165 W to 170 E The specified range can not be greater than 180 degrees Records less than a specified distance from the previous record may be excluded from the data analysis This is to prevent biasing when there is an uneven spatial distribution of observations To turn this option off select the OFF option You may also type a number rather than selecting from the list provided see Figure 2 20 Displays the results of the calculations i e the destination file contents A sample result file is shown in the appendix 45 Table 2 1 Sample Output from Calculate Stat
20. site follow the SEA ICE OBSERVATIONS link and follow the instructions The CD ROM which also contains an interactive tutorial for conducting sea ice observations and an image library and bibliography of sea ice terms is available from Dr Anthony Worby Antarctic Cooperative Research Centre University of Tasmania PO Box 252 80 Hobart Tasmania 7001 AUSTRALIA Email A Worby utas edu au Fax 461 3 6226 7650 To install the ice observation software download the following three files to a new directory on your PC Run the executable file seaice exe from Windows by double clicking the icon When you run the executable a new file seaice cfg will be created which stores the software configuration information This file is automatically updated when the user changes any default settings It is important to remember to delete this file before installing future upgrades of the seaice exe software i Seaice exe This is the executable version of the software ii grid vbx This is a system file that must be copied to enable the executable to run il landmask map This is a file of latitude and longitude points around the Antarctic coastline and is used for plotting purposes The following four files contain the blank observation spreadsheets and codes used for recording the ship based sea ice observations The completed forms should kept as a hard copy record of your observations i iceobs pdf Ice and meteorological observation lo
21. 1 indicates no data This is a drop list box from which the required code is selected Cloud in oktas code 0 8 A value of 1 indicates no data This is a drop list box from which the required code is selected The weather code is a two digit code from the Australian Meteorological Observers handbook The codes normally range from 00 99 however only the codes for weather conditions likely to be encountered in Antarctica are listed i e codes for unlikely events such as dust storms are not listed 36 2 3 2 Delete Record From the Record menu select the Delete Record option This allows an observation record to be deleted from the log file The dialog box shown in Figure 2 9 appears on the screen Select Record Ed Select A Record By Its Date Time Count Time Date 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 9 jun 1996 9 jun 1996 Cancel Delete Record Figure 2 9 Delete Record Dialog Box To delete a record select it by highlighting the appropriate time and date in the list box and then click the Delete Record button The program will prompt for confirmation before the record is removed from the database log file After the record is deleted the program will re calculate all track distances for the remaining records in the log file e Record Click on the date time list box to select the record to be delet
22. 1998 Results from work conducted in the Bellingshausen and Amundsen Seas are presented in Worby et al 19966 In the East Antarctic ship based sea ice observations have been collected on 18 voyages between October 1986 and August 1995 The voyage tracks are shown in Figure 4 1 and a summary of the seasonal coverage of the data are presented in Table 4 1 The combined data set from all voyages have been used to describe the seasonal cycle of the sea ice thickness distribution around East Antarctica The complete data set 1986 1995 comprises 2419 observations with the highest 3 091 Figure 4 1 Voyage tracks for 18 voyages to the East Antarctic pack ice between 1986 and 1996 on which ship based observations have been collected concentration of observations en route to and the location of the three Australian Antarctic stations The majority of the data have been collected during spring and most years have observations in October and November There are also observations in March April May September and December in some years The data have been categorised by month and binned into 0 2 m thickness categories The mean monthly ice and snow thickness distribution curves are shown in Figures 4 2 a and b There are sufficient data in seven months March April and August December to draw statistically meaningful conclusions about the thickness distribution of the sea ice and snow cover in th
23. 3 3919 1986 Hibler W D S J Mock and W B Tucker Ill Classification and variation of sea ice ridging in the western Arctic Basin J Geophys Res 79 18 2735 2743 1974 Jeffries M O and W Weeks Structural characteristics and development of sea ice in the western Ross Sea Antarct Sci 5 1 63 75 1992 Lange M A Antarctic sea ice its development and basic properties in Proceedings of the International Conference on the Role of the Polar Regions in Global Change pp 275 283 University of Alaska Fairbanks Fairbanks Alaska J une 1990 1991 Parkinson C L Sea ice in the polar regions a module in the CD ROM Sea ice in the polar regions and the Arctic observatory Consortium for International Earth Science Information CIESIN University Center Michigan 1996 Steffan K Atlas of the sea ice types Deformation processes and openings in the ice North Water project Z rcher Geographische Schriften 20 55 pp Geographisches Institut Eidgendssische Technische Hochschule Z rich 1986 Strass V H and E Fahrbach Temporal and regional variation of sea ice draft and coverage in the Weddell Sea obtained from upward looking sonars in J effries M O ed Antarctic Sea Ice Physical Processes Interactions and Variability Antarctic Research Series 74 123 139 1998 Tucker W B Ill W Govoni Morphological investigations of first year sea ice pressure ridge sails Cold Reg Sci
24. 94 18814 sao Jeo n n A W g lt weak 1504 C 0 996 1514 0 60 Te 3514 w COST O 201 18 CT 0 T 0 gor A213 soxeoued SE IN SLA esnys Zeg 01 43 AMAL AJI Meteorological Observation Codes The meteorology codes are used to describe the weather conditions at the time of the sea ice observations They are taken from the Australian Bureau of Meteorology Observers Handbook Only those conditions pertinent to Antarctic conditions are reproduced here Cloud Development During Past Hour Codes 00 03 00 Cloud development not observed or not observable 01 Clouds dissolving or becoming less developed 02 State of sky on the whole unchanged 03 Clouds forming or developing Fog Precipitation During Past Hour But Not At Time Of Obs 20 28 20 Drizzle not freezing or snow grains 21 Rain not freezing or snow grains 22 Snow not freezing or snow grains 23 Rain and snow or ice pellets 24 Drizzle or rain freezing 25 Showers of rain 26 Showers or snow or of rain and snow 27 Showers of hail or of hail and rain 28 Fog in the past hour not at present Blowing or Drifting Snow 36 39 36 Drifting snow below eye level slight moderate 37 Drifting snow below eye level heavy 38 Blowing snow above eye level slight moderate 39 Blowing snow above eye level heavy Mist 41 49 41 Fog in patches visibility 1000 42 Fog thin
25. ANTARCTIC ANTARCTIC CRC C R COOPERATIVE RESEARCH CENTRE FOR THE ANTARCTIC AND SOUTHERN OCEAN ENVIRONMENT A Technique for Making Ship Based Observations of Antarctic Sea Ice Thickness and Characteristics PART Observational Technique and Results ANTHONY WORBY IAN ALLISON PART User Operating Manual ANTHONY WORBY VITO DIRITA Antarctic CRC and Australian Antarctic Division GPO Box 252 80 Hobart Tasmania 7001 Australia Antarctic CRC GPO Box 252 80 Hobart Tasmania 7001 Australia Research Report No 14 ISBN 1875796 09 6 ISSN 1320 730X May 1999 This report details a technique for making systematic and quantifiable observations of sea ice thickness and characteristics from ships transiting the Antarctic pack ice This observation protocol has been endorsed by the SCAR ASPeCt Antarctic Sea ice Processes and Climate program as the preferred method for conducting ship based observations of sea ice characteristics Part is a complete description of the observational method It presents the codes used for quantifying the ice and snow parameters such as thickness floe size and topography and provides guidelines for observers to follow when making the observations Results from observations made in the East Antarctic pack are shown including the observed seasonal cycle of sea ice and snow thickness distribution for the period 1986 1996 A set of blank observation sheets are provided i
26. L 3 0 2 1 2 2 2 3 2 4 2 5 2 6 The main screen layout The FILE menu 2 2 1 Open observation log 2 2 2 Convert to text file 2 2 3 Import old database file The RECORD Menu 2 3 1 Add new record 2 3 2 Delete record 2 3 3 Edit record The GRAPHS Menu 2 4 1 Plot ship route 2 4 2 Plot sea ice data The CALCULATE Menu 2 5 1 Sea ice statistics The OPTIONS Menu 2 6 1 Input validation control 2 6 2 Albedo values 2 6 3 Observation record defaults APPENDIX 1 3 1 3 2 3 4 3 5 3 6 3 7 3 8 Calculating sea ice statistics 3 1 1 Notation 3 1 2 Type concentration matrix 3 13 Algorithms Database log file structure Config file structure Check and validation rules 3 4 1 General checks 3 4 2 Ice type checks 3 4 3 Total ice concentration Ice observation codes 3 5 1 Ice type codes ty 3 5 2 Floe size codes 1 3 5 3 Topography codes t 3 5 4 Snow type codes s 3 5 5 Open water codes OW Meteorological observation codes 3 6 1 Cloud development during past hour 00 03 3 6 2 Fog Precipitation during past hour but not at time of obs 20 28 3 6 3 Blowing or drifting snow 36 39 3 6 4 Fog Mist 41 49 3 6 5 Precipitation as drizzle 50 59 3 6 6 Precipitation as rain not showers 60 69 3 6 7 Frozen precipitation not showers 70 79 3 6 8 Precipitation as showers 80 90 3 6 9 Visibility Map plotting coordinate transformation 3 7 1 North or south pole 3 7 2 Calculate
27. Matrix Calculate the Type Concentration matrix this is a matrix of 10 3 dimensions 10 ice types 3 snow thicknesses 0 cm 0 3 cm gt 3 cm The table of albedo coefficients for each of the 10 ice types and 3 snow thicknesses is shown in the previous section See Figure 2 22 Coeff sz Table of albedo coefficients depending on the snow thickness 52 and the ice type ty classification Note that the function Coeff returns 3 values the row 1 10 ice type ty the column 1 3 snow thickness 0 cm 0 3 gt 3cm and the albedo coefficient coeff TypeCon 10 3 Type concentration matrix this is used for output to a file and for the calculation of the other parameters Refer to algorithm A 3 1 3 Algorithms From the TypeCon 10 3 matrix we can calculate all remaining parameters as described in algorithm B Algorithm A Calculate The TypeCon 10 3 Matrix SumAviceThickT ot 0 SumAvS noThickTot 0 SumAvAlbedo 0 SumP erAreaR idged 0 Repeat for each observation Read from the log file 52 y 6 cc TypeCon 1 1 TypeCon 1T1 10 cc SumAvAlbedo SumAvAlbedo 10 cc 0 07 for j 1 to 3 coeff row col 52 TypeCon rowl col 6 SumAviceThickTot SumAviceThickTot Cj Zj SumAvSnoThickTot SumAvS noThickTot 52 SumAvAlbedo SumAvAlbedo coeff SumPerAreaRidged S umP erAreaR idged 53 Algorithm B Calculate The Albedo and averages s
28. age must be completed in order to uniquely identify a record using the time and date fields When a new record is added to the file the record is inserted into the file in chronological order not necessarily at the end of the file The track distances are recalculated for the entire file when this occurs Ice Observation This page is used to record the hourly ice observations Data entry is via a series of dialog boxes Note that it is not essential to enter ice data to create a valid record but if no ice data are available the No Ice Observation box must be checked Met Observation This page is used to record the meteorological data Note that met data may be recorded in the absence of ice data if necessary Note that it is not essential to enter met data to create a valid record but if no met data are available the No Met Observation box must be checked 32 Seaice Windows Application Figure 2 6 General Information Page e Hour Minute The time of the observation is in hours and minutes and entered in 24 hour clock time e g 06 15 17 23 etc Day month year The date of the observation is entered as day month year eg 1 1 1997 30 12 2001 The year must be entered as a four digit number between 1900 and 2100 The date and time are used to uniquely identify each record Lat dd mm The latitude is entered in degrees minutes The range is 0 89 degrees 0 59 minutes North and south can be specified using the check box T
29. aph follow the procedure below Load Click on this button to select the log file to plot The file browser dialog box shown in Figure 2 15 will appear on the screen select the log file you wish to plot The file will initially be loaded but not plotted until the x axis is specified Figure 2 15 Selecta og file to plot 41 Plot Sea Ice Observations Database CAANTHONYVICEOBS 1 AUSTDA 1 AA070895 L06 o LA Na af 1000 Figure 2 16 Plotsea ice data X Axis If you wish to plot the entire file i e particular parameter s from every record in the file click on Plot Entire File Otherwise you may highlight a subset of the data by time and date as shown in Figure 2 17 Figure 2 17 X Axis Dialog Box 42 Y Axis Any of the ice or met data may be plotted the y axis The following dialog box displays the y axis set up and contains a list of items which may be plotted along the y axis More than one item may be plotted at any time Y Axis Options Ea Horizontal grid lines 40 Click item below to change Plot Status ESE MI Total Conc Tot Conc Open Water Op Water Track Distance Track Km i Ice Conc Pri Conc i Ice Type Pri Ice i Ice Thickness Pri Z cm i Floe Size Pri Floe i Topography Topo i Snow Type i Snow i Snow Thickness i S cm Ice Conc Ice Type Ice Th
30. c sections of the record click on any of the five buttons View Pri View Sec View Ter View Met or Comments 2 2 2 Convert To Text File From the File menu choose the Convert to Text File option The dialog box shown in Figure 2 3 appears on the screen This function is used to generate printable text files from binary database log files 2 7 Generate Text File From Database Time Field Latitude Field Longitude Field Ice Total Cone Ice Open Water Ice Track Distance Pri Ice Conc Pri Ice Thickness ee Pri Floe Size Pri Topography Figure 2 3 ConvertTo Text File Source Database File name This box displays the name of the database log file to convert from It will initially be blank Click on the lt lt button to select a log file A file browser box will appear similar to that shown in Figure 2 2 Selecta file with the extension log When the file is loaded the Dates From To will default to the first and last record in the file Destination Text File This is the name of the destination text file The default file name will be identical to the log file but with the extension txt Click on the lt lt button to change the name of the destination file Date gt gt From This specifies the first record of the file to be converted to text Pressing this button will display a dialog box with a list of records in the file Select the required record Refer t
31. calculation The ratio of ice below sea level ice above is defined as 1 0 16 1 18 r 4 3 3 1 based on the mean and snow thicknesses given above The value r 4 3 compares well with the value of 4 used by Dierking 1995 which was based on drilled transect measurements by Lange and Eicken 1991a and Wadhams et al 1987 The model formulation to calculate the average thickness of ridged floes 7 can now be written as 2 z r 0 5 RS z 3 2 where is the areal extent of surface ridging S is the average sail height of ridges and 2 is the thickness of level undeformed ice in the floe 3 4 Calculating area averaged albedo The area averaged albedo is computed from the ice concentration and allwave albedo for each ice type The allwave albedo values for different ice and snow thickness categories were originally taken from Allison et al 1993 however these have recently been updated Warren personal communication 1998 The average albedo is calculated over the entire pack including the open water fraction A value is calculated at each hourly observation site from which zonal averages may also be calculated 4 0 TYPICAL RESULTS A summary of the results from ship based observations collected in the East Antarctic pack ice is presented to indicate the usefulness of the data For a complete presentation of results readers are referred to Allison et al 1993 Allison and Worby 1994 and Worby et al
32. ce thickness in the Antarctic Cold Regions Sci Technol in press Worby 0 Jeffries W Weeks Morris and J afia The thickness distribution of sea ice and snow cover during late winter in the Bellingshausen and Amundsen Seas Antarctica J Geophys Res 101 C12 28 441 28 455 1996b Worby A P Massom I Allison V Lytle and Heil East Antarctic sea ice A review of its structure properties and drift in Antarctic sea ice physical processes interactions and variability Antarct Res Ser 74 edited by O Jeffries pp 41 67 American Geophysical Union Washington D C 1998 12 7 0 APPENDIX 1 BLANK OBSERVATION SHEETS AND CODES 13 GAL lt lt LAL 95 15319345 SI JOI VIS ANVWIId 41451 ppp pp 7 AUYUVILYAL AUVGNODAS ASIVIAT Id 005 8907 6 0297 214 SNOLLVAIASSO AOI VAS NOLLISOd 2 N3AIO SI 2 343530 ANG lt ONIMOTIOS JHL JAY 38 AVIA SIN3ININOO TVNOILICQV SUPLA A 8 49 p ds 59 09 KZ SON 1994 13 5 OLOHd SNOLLVAYASHO TVOIOO IONO LLAIA B 7 SIN3ININOO vos uod 33 9 Aq eAuA od e1seooyeAuATOqd
33. char comments 200 char 50 llif the obse rvation was made observation time and date latitude of the observation Hongitude of the observation sea temperature C lair Iva Ifilm valid inva Ifilm frame valid inva Ilvideo reco inva veloc inva direc inva id sea temp data mperature in C id air temp data ity in m s id wind velocity ion in degrees id wind direction roll number id photo film counter id photo frame rder counter id video counter visibility code IIcloud cover code I weather code Icomments Ispare field The complete observation record written to disk file struct LOG RECORD ICERECORD icerecord METRECORD metrecord 3 3 Config File Structure field 5 for future use The config file comprises the individual records written to a single file called seaice cfg The following records are stored the same sequence as listed Data validation record struct VALRECORD VALIDATION_STYLE iceThick2000 VALIDATION_STYLE snowThick300 VALIDATION STYLE totlcelsS um VALIDATION_STYLE snowlceThick js 75 VALIDATION STYLE priSecTerThick 75 VALIDATION STYLE iceThicklceType VALIDATION STYLE iceTypeChecks 10 VALIDATION STYLE totalConcChecks 6 I GENERAL CHECKS Icheck for ice thickness 2000 cm
34. condary is specified sum pri Ice Thickness pri gt sec gt ter The ice thickness values must be in order of primary gt secondary gt tertiary e Ice Thickness gt snow thickness The ice thickness must be gt snow thickness Ice thickness matches ice type The ice thickness must be consistent with the ice type specified For example if the ice type selected is young grey ice the ice thickness must be 10 15 Ice Type Checks For each ice type there is a corresponding set of ice parameters each of which has a defined range of values When you click on each of the ice types the acceptable range of values of each corresponding parameter are displayed Clicking on the ice type will switch the validation controls between YES NO and WARNING ONLY For example Ice type is Check that nilas floe size 200 topography 100 400 500 600 snow type 1 2 3 ice thickness cm snow thickness Total ice concentration checks For each value of total ice concentration there is a corresponding range of values for open water When you click on the total concentration list the acceptable range of values for open water are displayed Clicking on the ice type will switch the validation controls between YES NO and WARNING ONLY For example Total ice conc is Check that 4 10 Open water value 4 5 6 Note that the configuration of validation controls may be stored so that next time the program runs the set up informa
35. e lt 10 cm 3 45 0 00 0 00 Nilas lt 10 cm 19 03 0 00 0 00 Grey Ice 10 15 cm 1 59 3 81 0 71 Grey White 15 30 cm 0 80 5 22 9 47 1st Y ear 30 70 cm 0 00 2 12 11 50 1st Year 70 120 cm 0 00 0 88 9 20 Ist Year gt 120 cm 0 00 0 00 11 86 Multiyear Ice 0 00 0 00 0 09 Brash 0 44 0 00 0 00 Fast Ice 0 00 0 00 0 00 46 Coefficients Process A full description of all calculations is given in Appendix Algorithms and software also included A sample Part of this report for more information Pressing this button will process the log file The results are saved to the destination file and displayed in the sea ice statistics box output file is shown in Table 2 1 2 6 The OPTIONS Menu 2 6 1 Input Validation Control From the Options menu select the Input Validation Control option This menu function is used to enable or disable various validation checks when the user is entering a new observation record The dialog box shown in Figure 2 21 will appear Each validation check has three settings YES enabled Forces the user to provide input data consistent with the prescribed checks NO disabled Ignores the validation check WARNING ONLY Identifies data inconsistent with the prescribed checks but enables the user to overwrite them General Checks Ice Thickness Check lt 20 meters Snow Thickness Check lt 3 meters Total Ice Conc Pri Sec Ter Ice Conc Pri gt Sec
36. e for primary or secondary or tertiary ice 100 to 800 Code 0 identifies no data Topog Drop list box to select topography code for primary or secondary or tertiary 100 to 897 If topography 2 500 it will prompt for the x and y components x areal coverage y mean sail height Code 0 identifies no data Snow Type Drop list box to select snow type code for primary or secondary or tertiary ice 0 to 10 Code 0 identifies no data 34 Ice Thick Ice thickness in cm for primary or secondary or tertiary ice drop list box 0 to 2000 cm Snow Thick Snow thickness in cm for primary or secondary or tertiary ice drop list box 0 to 300 cm No Primary Ice Obs If no primary ice observation is available click on this check box All primary ice input fields will be disabled Note that in this case the No ice observation box should be checked No Secondary Ice Obs If no secondary ice observation is available click on this check box All secondary ice input fields will be disabled No Tertiary Ice Obs If no tertiary ice observation is available click on this check box All tertiary ice input fields will be disabled After completing the required input fields for the ice observation you must proceed to the met observation page to enter any meteorological data or to specify that none are available At this point the program will check that all the required ice data are supplied and valid It will then app
37. ean thickness of the level ice within the pack To account for the mass of ice in ridges the observations described in section 2 5 are used in conjunction with a simple model to calculate a corrected mean thickness 2 The model takes the undeformed floe thickness 2 average sail height S and an estimate of the areal extent of surface ridging H as input parameters and calculates the mean thickness of the floe z assuming a triangular sail isostasy and a ratio of ice and snow above sea level to ice below sea level as 5 1 The assumption of a triangular sail cross section is consistent with the formulation of Hibler et al 1974 for calculating the effective thickness of ridged ice Their formulation used a fixed slope angle of 26 however the present study uses an implied variable slope angle which is dependent upon the areal coverage of ridges and the average sail height In this way broader ridges are flatter which is consistent with the theory that ridges should build laterally once the limiting height is reached Tucker and Govoni 1981 The assumption of a triangular ridge is therefore not likely to induce large errors Published literature on sea ice density is sparse however Buynitskiy 1967 presented mean densities from East Antarctic sea ice for summer and winter ice of 875 kg m and 920 kg m respectively and these are consistent with the value of 900 kg m used in the model formulation The assumption of hydrostatic equilibri
38. ed Delete Record This button is used to delete the selected record 2 3 3 Edit Record From the Record menu select the Edit Record option This allows an observation record to be individually edited from the log file The dialog box shown in Figure 2 10 appears on the screen To edit a record select it by highlighting the appropriate time and date in the list box and then click on the Edit Record button The record is edited in the same manner as described in section 2 3 1 Add New Record except that all the fields in the record are initialised with the contents of the record in the log file Once the record is edited the program will re calculate all track distances for all the records in the log file Note that the record is identified by the time date fields changing these fields will delete the original record specified and add a new record with a new time date e Record Click on the date time list box to select the record to be edited e Edit Record This button enables the selected record to be edited 37 Select Record x Select A Record By Its Date Count Time Date 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 87 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 9 jun 1996 9 jun 1996 Cancel Edit Record Figure 2 10 EditRecord Dialog Box 2 4 The GRAPHS Menu 2 4 1 Plot Ship Route Database files can be plotted on a geographic map generally
39. ed the following checks apply 3 4 1 General Checks e the required data are supplied An error message is displayed if any data field has not been specified All the supplied data are within their specified range Thus the time must be lt 23 59 the day lt 31 month lt 12 etc The ice thickness must be lt 2000 cm and the snow thickness lt 300 cm An error message is displayed if any entry is not specified correctly e The total ice concentration must equal the sum of the individual ice concentrations thus primary secondary tertiary total e The primary ice thickness gt secondary ice thickness gt tertiary ice thickness The ice thickness should normally be greater than the snow thickness A warning message is displayed if this is not the case however the user can choose to ignore the warning message if the observation is correct e The specified ice thickness must be consistent with the specified ice type category Thus if the ice type is 40 Young grey ice 10 15 cm then the ice thickness must be the range 10 15 cm 56 3 4 2 Ice Type Checks Frazil Shuga Grease Nilas Pancakes Young grey 10 15 Grey white 15 30 1st Year ice 30 70 1st Year ice 70 120 1st Year ice gt 120cm Multi Year ice 85 Floe size Topography snow type ice thickness Snow thickness Floe size Topography snow type ice thickness Snow thickness Floe size Topography snow type ice th
40. efreeze as quickly as observed in August increasing the amount of ice less than 0 7 m thick Second the ice does not grow to the same thickness primarily because of increased radiation and warmer air temperatures As a result there is more open water and thin ice within the pack typically with a thinner snow cover As the pack diverges ice is slower to form leading to an increase in the open water fraction and a subsequent warming of the surface ocean water This is a positive feedback which further limits ice production and may result in some ice melt The distribution curve for December reflects this showing the greatest open water fraction no ice thinner than 0 2 m and a considerable decrease in the ice types thinner than 0 6 m The ice thickness distribution curves for the intervening months are consistent with the discussion above April shows a flatter distribution than March which is indicative of less new ice growth over large areas and the formation of thicker ice by dynamical processes The September curve flattens between the thinnest category and the 0 4 0 6 m category which is consistent with the trend between August and October November in turn shows an increase in open water fraction and further flattening of the distribution curve in response to the divergence of the pack and limited new ice growth The surface topography observations used as input to the ridging model described in section 3 3 have been Collected on voyages
41. es to be identified and fixed at the time of the observation The data quality checks are described in section 6 1 Data entry is via a series of dialog boxes thus reducing the possibility of input errors by the user Initial data processing can be completed during the voyage Calculations include mean ice and snow thicknesses and the fraction of different ice types within the pack These can be calculated on the entire data set or any Subset of it defined by a range of dates or latitude and longitude Furthermore the statistics may be calculated on multiple data files The program can plot sea ice and meteorological observations on an XY Cartesian graph and geographical plots to show ship tracks on a polar stereographic map south only Geographical plots may include the Antarctic coastline and station locations 1 2 Data File Format The program stores observation records to a disk file in binary format Thus the files cannot be viewed or printed directly The reason for using a binary file format is to simplify reading and writing complex data records to disk reliably and rapidly The program provides a facility to create text file listings from binary data files These text files can be viewed and printed The minimum hardware configuration to run the program is e BM PC or compatible with 4MB of memory e Windows 3 11 or higher e Colour graphics display with pixel resolution better than 800 x 600 16 colours Screens with a lo
42. f no data are available click on the check box to the right of the sea temperature input box This check box may be disabled by default refer to section 2 6 3 A warning message appears if the sea temperature is outside the range 2 2 The wind speed in meters second If no data are available click on the check box to the right of the wind speed input box This check box may be disabled by default refer to section 2 6 3 A warning message appears if the wind speed is gt 25 m s The wind direction in metres second The range is 0 to 359 degrees relative to north i e T entered as an integer If no data are available click on the check box to the right of the wind direction input box This check box may be disabled by default refer to section 2 6 3 The photo film number Any integer is allowed If no data are available click on the check box to the right of the photo film number input box This check box may be disabled by default refer to section 2 6 3 The photo frame number Any integer is allowed If no data are available click on the check box to the right of the photo frame number input box This check box may be disabled by default refer to section 2 6 3 The video tape counter This must have the format hh mm ss If no data are available click on the check box to the right of the video tape counter input box This check box may be disabled by default refer to section 2 6 3 Visibility code 90 97 A value of
43. fault no air temperature to no data This means that when entering a new record the air temperature in the met observation dialog box has a default value of N A not available Note that when entering a new record the user may override this default setting by unchecking the N A box and entering a value Chec Chec Chec Chec Chec Chec kth kth kth kth kth kth is box to set the defau is box to set the defau is box to set the defau is box to set the defau is box to set the defau is box to set the defau 51 tfor the sea temperature field to N A tfor the wind speed field to N A tfor the wind direction field to N A photographic film number to N A t for photographic frame number to N A tfor the video counter to N A 3 0 3 0 SOFTWARE ALGORITHMS AND CHECK CODES 52 3 1 Calculating sea ice statistics 3 1 1 Notation The equations for calculating the sea ice statistics assume that all the input data are correct The following notation is used in all equations ice concentration j 1 primary 2 secondary 3 tertiary ice 2 ice thickness in metres j l primary 2 secondary 3 tertiary ice 57 snow thickness in metres 1 primary 2 secondary 3 tertiary ice X areal coverage parameter x 100 tyice type classification j 1 primary 2 secondary 3 tertiary ice N total number of observations CC total ice concentration for an observation 3 1 2 Type Concentration
44. g sheets ii comm xls pdf Comments log sheet 1 icecodes pdf Ice observation codes metcodes pdf Meteorological observation codes Parts and II of this report are contained in the file i report pdf Parts and Il of this report Antarctic CRC Research Report 14 TABLE OF CONTENTS Abstract Access to software and related files PART OBSERVATIONAL TECHNIQUES AND RESULTS 1 0 INTRODUCTION 2 0 OBSERVATIONAL TECHNIQUE 2 1 Ice concentration 2 2 Ice type ty 2 3 Ice thickness 2 24 Floe size f 25 Topography t 2 6 Snow type s 275 Snow thickness sz 2 8 Open water 2 9 Meteorological observations 2 10 Photographic records 21 Comments 3 0 DATA ENTRY AND PROCESSING 31 Quality control 32 Editing data 3 33 Estimating area averaged ice and snow thickness 34 Calculating area averaged albedo 4 0 TYPICAL RESULTS 5 0 ACKNOWLEDGEMENTS 6 0 REFERENCES 7 0 APPENDIX 1 11 Blank ice observation sheet 12 Blank met observation sheet 73 Blank comments sheet 74 Ice observation codes 75 Met observation codes 76 Visibility codes 8 0 APPENDIX 2 8 1 Example of completed ice observation sheet 8 2 Example of completed met observation sheet 8 3 Example of completed comments sheet PART USER MANUAL 1 0 INTRODUCTION 11 General description 1 2 Data file format 13 Installation Ui amp gt UC C C O O 10 24 25 25 25 25 2 0 USER MANUA
45. ght hours a photographic record of ice conditions can be kept Slides are usually taken from the bridge at the time of each observation and the log book has a column for recording film and frame numbers There is also scope for recording the frame number for a time lapse video recorder which the authors have mounted on the ship s rail This captures a single video frame every 8 seconds providing a comprehensive visual record of ice conditions on a single video tape for each 30 day period This photographic archive is not generally used for quantitative analyses but provides an excellent reference that can be used in conjunction with the ship based observations At night the camera is angled closer to the ship to view an area that can be adequately lit by flood lights mounted on the ship s rail 2 11 Comments In addition to the hourly observations entered by code there is scope for additional comments to be recorded These usually include a brief description of the characteristics of the pack in particular features which are not covered by the observation codes such as frost flowers on dark nilas or swell penetrating the pack Brief details of sampling sites buoy deployments or other on ice activities may also be recorded and if necessary a comment on how typical the ice along the ship s route is of the surrounding region The Ref no column enables the observer to easily reference comments made on the Additional Comments proforma 3 0 DATA ENTRY
46. graphic coordinates This conversion produces no distortion at latitudes of 70 degrees south or north hence there is minimal distortion within the Antarctic sea ice zone The earth is assumed to be an ellipsoid with a radius of 6378 273 km and eccentricity e of 0 081816153 if at 90 tang 4 lat 2 G 2 lt 1 0189 ecsh 85 tang 4 S _ 2 1 6 0 62 95 m 4 0 exi 5 _ e E G p lt sygnesn or XLAM G p odon XLAM if at 90 Gres Go 3 8 Track Distance Calculations To calculate the distance between two points lat1 lon1 and lat2 lon2 on the earth we use the following equations Itis assumed that the points are close to each other The notation used is earth radius 6378 273 km earth eccentricity 0 081816154 lat lon geodetic coordinates 3 8 1 Latitude distance 2 Rode d9 1 co 9 where 0 Bt lat all values are in radians 3 8 2 Longitude distance Re 1 cof T 952 1 ca 8 where 0 2 lat d 0 3 8 3 Track distance ds as 63
47. he latitude may also be entered in decimal degrees i e dd ddd see section 2 6 3 A warning message will appear if the latitude and longitude occur elsewhere in the data base Lon ddd mm The longitude is entered in degrees minutes The range is 0 179 degrees 0 59 minutes East and west can be specified using the check box The longitude may also be entered in decimal degrees i e ddd ddd see section 2 6 3 A warning message will appear if the latitude and longitude occur elsewhere in the data base 33 Seaice Windows Application Figure 2 7 Ice Observation Page Note that the codes for all ice types floe sizes topography snow type and open water are listed in the appendix No Ice Observation If there is no ice observation as distinct from no ice at the time of the observation then this box should be checked Total Ice Conc Drop list box to select the total ice concentration between 0 and 10 This value must equal the sum of the primary secondary tertiary ice concentrations Open Water Drop list box to select open water code 0 to 9 Comments Comments for this ice observation to a maximum of 120 characters Ice Conc Drop list box to select ice concentration for primary or secondary or tertiary ice 0 to 10 Ice Type Drop list box to select ice type code for primary or secondary or tertiary ice 10 to 95 Code 0 identifies no data Floe Size Drop list box to select floe size cod
48. ickness Floe Size Topography 20 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 booooooooooooooo Cancel D Figure 2 18 Y Axis Dialog Box Horizontal Grid Lines The number of grid lines may be selected from the combo box or a number can be typed in Click an item to change plot status Highlighting any one of the parameters in this list box will display the dialog box shown in Figure 2 19 The dialog box has a range of options To plot the selected parameter check the Plot it box The upper and lower plot ranges may be specified as well as the line colour and thickness and marker style Different marker shapes can be used to better display plots on lower quality monitors On monitors that do not support more than 16 colours some colours will not be displayed correctly Button This is a scroll left button if you are plotting a large file and viewing only a small section of that file it is possible to scroll backward and forward using this button and the Button The graph will scroll by one page where one page is equal to the number of points plotted on the x axis gt gt Button Scroll right button See description above 43 Y Axis Item Figure 2 19 Single Y Plot Dialog Box 2 5 The CALCULATE Menu 2 5 1 Sea Ice Statistics From the Calculate menu choose the Sea Ice Statistics option The dialog box shown in Figure 2 20 will a
49. ickness Snow thickness Floe size Topography snow type ice thickness snow thickness Floe size Topography snow type ice thickness snow thickness Floe size Topography snow type ice thickness snow thickness Floe size Topography snow type ice thickness snow thickness Floe size Topography snow type ice thickness snow thickness Floe size Topography snow type ice thickness Snow thickness 57 0 0 1 lt 10 0 cm 200 100 400 500 600 1 2 3 lt 10 lt 3 100 400 100 200 1 2 3 4 10 20 cm 10 cm 200 400 700 100 500 700 z1 2 3 4 10 210 15 cm 10 cm 200 400 700 100 500 700 1 2 3 4 10 15 30 cm 20 200 400 800 100 500 800 1 2 3 4 10 11 30 70 cm lt 40 400 800 100 500 800 2 3 4 10 11 70 120 60 400 800 500 800 2 3 4 10 11 120 300 cm lt 100 400 800 100 500 800 2 11 lt 2000 300 Brash ice 90 Floe size Topography snow type ice thickness snow thickness Fast ice 95 Floe size Topography snow type ice thickness Snow thickness 3 4 3 Total Ice Concentration 0 Check open water 6 9 1 2 Check open water 6 8 3 4 Check open water 4 6 5 7 Check open water 2 6 8 9 Check open water 1 4 10 Check open water 0 1 3 5 Ice Observation Codes 3 5 1 Ice Type Codes ty 0 No data 10 Frazil 11 Shuga 12 Grease 20 N
50. ickness data into a simple model see Section 3 3 Table 2 1 Ice thickness classifications used for the ship based observations Ice Type Classification Ice Thickness m Code Fazil 10 Shuca 91 11 New ice Grease 12 Nila 20 Pancakes lt 0 2 30 Young grey ice 0 10 0 15 40 Young grey white ice 0 15 0 3 50 First year ice 0 3 0 7 60 First year ice 0 7 1 2 70 First year ice gt 1 2 80 Multi year ice lt 20 85 Brash lt 0 5 90 Fastice lt 3 95 Range is a guide only and may be exceeded Thinner snow free ice categories which are particularly important for ocean atmosphere heat exchange can be reliably classified by a trained observer from their apparent albedo while the thickness of very thick floes may be estimated by their freeboard The accuracy of careful observations will be within 10 20 of the actual thickness and a large sample of observations can be expected to provide a good statistical description of the characteristics of the pack This is particularly true at the thin end of the thickness distribution where changes are most important for both radiant and turbulent heat transfer 0 Worby and Allison 1991 On dedicated scientific voyages it is usually possible to make regular in situ measurements of ice and snow thickness both on level ice and across ridges to calibrate the ship based observations Worby et al 1996b demonstrated a technique for combining in situ and ship based observations to estimate the ice th
51. ickness distribution in the Bellingshausen Sea Dedicated scientific voyages also usually provide the opportunity to follow specific routes to optimise data quality which may be compromised if the ship follows the most easily navigable routes It is the observer s responsibility to clearly indicate on the observation sheet when the ship is preferentially following leads so that this may be considered during data processing 2 4 Floe size f Floe size can be difficult to determine because it is not always clear where the boundary of a floe is located Cracks and leads delineate floe boundaries whereas ridges do not Where smaller floes have been cemented together to form larger floes the larger dimension is recorded but usually with a comment to indicate that smaller floes are visible Where two floes have converged and ridged the floe size is taken as the combined size of the two A good rule of thumb is if you could walk from point A to point then both points are on the same floe This guide can be helpful when trying to determine floe size The length of the ship about 100 m for most ice breakers can act as a good guide for estimating floe size The Ship s radar can be useful for determining the size of very large floes Floe size is recorded using a code between 100 and 700 New sheet ice code 200 is normally used for nilas This code does not specify floe size but is a descriptor for refrozen leads and polynyas It is often used in con
52. ilas 30 Pancakes 40 Young Grey ice 0 1 0 15 m 50 Young grey white ice 0 15 0 3 m 60 First year 0 3 0 7 m 70 First year 0 7 1 2 m 80 First year gt 1 2 85 Multi Year floes 90 Brash 95 3 5 2 Floe Size Codes f 0 No data 100 Pancakes 200 New sheet ice 300 Brash broken ice 400 Cake ice lt 20 m 500 Small floes 20 100 m 600 Medium floes 100 500 m 700 Large floes 500 2000 m 800 Vast floes gt 2000 m 58 300 0 1 lt 50 cm 0 800 100 500 800 2 11 lt 300 60 3 5 3 Topography Codes 1 0 No Data 100 Level ice 200 Rafted pancakes 300 Cemented pancakes 400 Finger rafting 5 New unconsolidated ridges no snow New ridges filled with snow snow cover Consolidated ridges no weathering 8 Older weathered ridges where X realCoverage o d Y S ilHeght T 10 20 2 2030 NOOB 3 30 40 pm 4 40 50 Zi EM 5 50 60 6 60 90 2e 7 70 80 i Red 8 80 90 5 Om 9 90 100 3 5 4 Snow Codes 5 Ra SSO Co cg UT No observation No Snow no ice or brash Cold new snow 1 day old Cold old snow Cold wind packed snow New melting snow wet new snow Old melting snow Glaze Melt slush Melt puddles Saturated snow waves Sastrugi 3 5 5 Open Water Codes OW SON OO ro O IEA O No openings Small cracks Very narrow brea
53. ile From the File menu select the Import Old Database Files option The dialog box in Figure 2 5 will appear This option is used to convert database files from older versions of the sea ice software to the new version of the sea ice software and will not be required by the vast majority of users Older versions of the sea ice software used data base files in text format Two separate data base files were used One containing the sea ice observations and the other containing meteorological observations The current version of Seaice exe uses a single binary data base format which combines the ice and met data into a single record The file extension used is log Import Old Database T ext Files View Edit Record For Identical Records Ho Md gt gt Update gt gt Confirm Before Replacing OK Indicates a record is found valid Selection Indicates no data E Add All Records No Confirm 21 ER Indicates record is error Round off Time to Nearest Hour Figure 2 5 Import Old Database Files Dialog Box 30 Figure 2 5 shows the dialog box used to convert old version database files to the new version files the left of the dialog box the user specifies the file names of the old met and ice data files and on the right the file name of the destinaton log file is specified If the log file exists the new records are appended to it or replace any existing records The fields are as follows e Import This pull
54. inuous 72 Moderate fall of snow flakes intermittent 73 Moderate fall of snow flakes continuous 74 Heavy fall of snow flakes intermittent 15 Heavy fall of snow flakes continuous 76 Ice prisms with without fog 71 Snow grains with without fog 78 Isolated starlike snow crystals 79 Ice pellets Precipitation As Showers 80 90 80 Slight rain showers 81 Moderate or heavy rain showers 82 Violent rain showers 83 Slight showers of rain and snow 84 Moderate heavy showers of rain and snow 85 Slight snow showers 86 Moderate or heavy snow showers 87 Slight showers of soft or small hail 88 Moderate heavy showers of soft small hail 89 Slight showers of hail 90 Moderate or heavy showers of hail Visibility Codes The visibility codes are used to estimate how far an observer can see from the ship s bridge 90 lt 50 91 50 200 92 200 500 93 500 1000 94 1 2 km 95 2 4 km 96 4 10 km 97 210 km 4 Not available 19 8 0 APPENDIX 2 EXAMPLES OF COMPLETED OBSERVATION SHEETS 20 lt Z lt 1A 553 15319346 JO SI JOI V3S SALON Ol e OL 4 96 lg d ec 2 g UE 14 v dap 995 5 w sb J p ot ww RP ES UON pps ee Ee a SESS RN
55. is region of the Antarctic ice pack Currently there is still a large gap the data set during the early winter months with very little or no data in May June and July By far the greatest seasonal changes in the ice thickness distribution are in the open water and thin ice categories The amount of open water decreases from almost 60 in December to little more than 10 in August and the thinnest ice thickness category 0 0 2 shows 30 seasonal change between December and March contrast the amount of ice greater than 1 0 m shows very little seasonal variability Table 4 1 Summary of the mean ice concentration and undeformed ice and snow thickness values from ship based observations Month Number of Number of Mean Ice Mean Ice Thickness Mean Snow Voyages Observations Concentration m Thickness m March 3 92 76 0 36 0 02 April 3 129 83 0 48 0 11 August 1 165 93 0 52 0 11 September 1 246 82 0 47 0 12 October 10 595 75 0 35 0 07 November 8 1129 64 0 36 0 07 December 4 63 43 0 31 0 07 The mean values are calculated over the entire pack ice including the open water fraction Note that the mean ice and snow thickness values for March exclude the anomalously thick multi year floes shown in Figure 12 observed on the March 1995 voyage near 150 E Fractional coverage September September October November November 0 4 0 2 0 0 0 6 December op December 0 4 9 04 0 2 8 0 2 5 8 0 0 0 0 gt
56. istics for Voyage Data from RSV Aurora Australis 2 26 October 1997 TOTAL OBSERVED AREA DATABASE C ASEAICE ICEOBS AA101097 L0G 113 OUTPUT C SEAICE ICEOBS AA101097 STA Date From ALL Date To ALL Latitude F rom ALL Latitude To ALL Longitude From ALL Longitude To ALL Exclude observations lt 11 0 km number of observations 113 Total ice concentration 80 09 Open water within pack 19 91 Av level ice thickness total area cm 27 49 Av level ice thickness ice area cm 34 32 Fraction of surface area ridged 0 06 Av ridged ice thickness total area cm 52 18 Av ridged ice thickness ice area cm 65 16 Av snow thickness total area cm 6 13 Av snow thickness ice area cm 7 65 Av snow thickness Snow covered area cm 11 16 Snow covered ice within pack total area 54 87 Snow free ice within pack total area 25 31 Percent ice with snow cover 68 43 Percent ice with no snow 31 57 Av albedo total area 0 46 Level Ice snow cover 0 3cm gt 3cm Water 19 91 0 00 0 00 New Ice lt 10 cm 3 45 0 00 0 00 Nilas lt 10 cm 19 03 0 00 0 00 Grey Ice 10 15 cm 1 59 6 55 2 92 Grey White Ice 15 30 cm 0 80 5 31 9 38 1st ear 30 70 0 00 0 18 18 67 1st Year 70 120 0 00 0 00 7 08 1st Year gt 120 cm 0 00 0 00 4 69 Multiyear Ice 0 00 0 00 0 09 Brash 0 44 0 00 0 00 Fast Ice 0 00 0 00 0 00 Ridged Ice snow cover 0 gt 3cm Water 19 91 0 00 0 00 New Ic
57. junction with topography codes 100 level ice and 400 finger rafting 2 5 Topography t As discussed above the ice thickness estimates are only made of the level ice in a floe This is because the thickness of ridges can not reliably be estimated from a ship since they tend to break up in to their component blocks when hit by the ship rather than turning sideways so that their thickness can be estimated However drilled transects across ridged ice floes indicate that the mass of ice in ridges is a major contributor to the total ice mass of the pack hence it is important to quantify the extent of ridging within the pack To do this the areal extent and mean sail height of ridges is recorded for each ice type within the pack The extent of surface ridging is estimated to the nearest 10 1 15 important that observers not look too far from the ship when estimating the areal extent of ridges otherwise only the ridge peaks are seen and not the level ice between them This gives a false impression of more heavily deformed ice than is actually present The mean sail height is estimated to the nearest half metre below 2 m and to the nearest metre above 2 m It is important to remember that it is the mean sail height that is recorded This can be difficult to estimate particularly in flat light when the sky is overcast Our experience has shown that ridge height is generally underestimated due to the vertical perspective from the bridge Ridges are cla
58. ks lt 50 m Narrow breaks 50 200 Wide breaks 200 500 m Very wide breaks gt 500 m Lead coastal lead Polynya coastal polynya Water broken only by small scattered floes Open sea 59 3 6 Meteorological Observation Codes 3 6 1 Cloud Development During Past Hour Codes 00 03 Cloud development not observed or not observable Clouds dissolving or becoming less developed State of sky on the whole unchanged Clouds forming or developing 3 6 2 Fog Precipitation During Past Hour But Not At Time Of Obs 20 28 Drizzle not freezing or snow grains Rain not freezing or snow grains Snow not freezing or snow grains Rain and snow or ice pellets Drizzle or rain freezing Showers of rain Showers or snow or of rain and snow Showers of hail or of hail and rain Fog the past hour not at present 3 6 3 Blowing or Drifting Snow 36 39 Drifting snow below eye level slight moderate Drifting snow below eye level heavy Blowing snow above eye level slight moderate Blowing snow above eye level heavy Fog in patches visibility 1000 Fog thinning in last hour sky discernible visibility lt 1000 m Fog thinning in last hour sky not discernible visibility 1000 Fog unchanged in last hour sky discernible visibility lt 1000 m Fog unchanged in last hour sky not discernible visibility 1000 Fog beginning thickening in last hour sky discernible visibility 1000 Fog beginning thickening in last hour sky not
59. ly the check rules described in Sections 2 6 and 3 4 and prompt the user if incorrect or anomalous entries are found Seaice Windows Application 1 Ho Observation CLOUD DEVELOPMENT WITHIH LAST HOUR 00 03 00 Cloud development not observed or not observable 01 Clouds dissolving or becoming less developed 02 State of sky on the whole unchanged 03 Clouds forming or developing FOG OR PRECIPITATIOH WITHIH LAST HOUR 20 28 20 Drizzle not freezing or snow grains 21 Rain not freezing or snow grains 22 Snow not freezing or snow grains 23 Rain and snow or ice pellets ____ 25 Showers of rain 26 Showers of snow or of rain and snow 210 s of hail or of hail and rain gt Figure 2 8 Met Observation Page 35 No Met Observation Air Temp Sea Temp Wind Speed m s Wind Direction 0 359 Photo Film No Photo Frame No Video Tape Counter Visibility Code Cloud Oktas Weather Code If no met data are available simply click this check box All other controls become invisible This means that the record will not contain any met data The air temperature in C If no data are available click on the check box to the right of the air temperature input box This check box may be disabled by default refer to section 2 6 3 A warning message appears if the air temperature is gt 5 C The sea temperature in C I
60. mary Ice Observation Data Secondary Ice Observation Data Tertiary Ice Observation Data Meteorological Observation Data or Ice Observation Comments depending on which of the five buttons above is selected Primary Secondary Tertiary ice Displays the record number time latitude longitude and total ice concentration Additionally the ice concentration ice type and thickness floe size topography snow type snow thickness distance along track from the first observation and open water codes are displayed for each of the primary secondary and tertiary ice types The ice and snow thickness values are in units of cm All other entries are in the specified codes Meteorological Data Displays the record number time latitude longitude sea temperature air temperature wind speed wind direction photo film photo frame numbers video counter visibility cloud cover and current weather codes Comments Displays the record number time latitude longitude and comments from the ice observation record 26 Months List box Day List box e Year List box e Font Size box 2 2 The FILE Menu 2 2 1 Open Observation Log To display the data for a different month click on the month and the list box to the right Day will display the number of daily records for that particular month Click on one of the days listed to display the contents on screen To display the data for a different day click on the day number
61. mpossible The ship based observing scheme presented in this report provides a consistent and quantifiable method for estimating the thickness and distribution of sea ice along a ship s track through the pack ice The scheme involves making hourly observations from the ship s bridge entered using a series of classification codes for each parameter Information on snow cover type and thickness are also recorded Software for PC is available for entering quality controlling and conducting preliminary analyses of the data while in the field The observations may be made by a trained observer from any ice capable vessel operating within the Antarctic pack ice zone Frequently repeated shipping routes to Antarctic coastal stations provide an opportunity to obtain data which may identify seasonal and possibly inter annual changes in ice conditions Observations from multiple voyages within the pack ice may enable the identification of regional differences 2 0 OBSERVATIONAL TECHNIQUE A standard set of observations are made hourly by an observer on the ship s bridge These include the ship s position and total ice concentration and an estimate of the areal coverage thickness floe size topography and snow cover of the three dominant ice thickness categories within a radius of approximately 1 km of the ship The three dominant ice categories are defined as those with the greatest areal concentration and the thickest of these is defined as the primary ice t
62. n Appendix 1 Examples of completed observation sheets are presented in Appendix 2 Part is the user operating manual for the purpose designed computer program for entering quality controlling and processing the ship based observations on PC The software proformas have a similar layout to the hand written observation sheets The software runs on PC under Windows 3 11 or higher and is written in microsoft visual C version 1 5 2 This report should be read in conjunction with the CD ROM Observing Antarctic Sea Ice A Practical Guide for Conducting Sea Ice Observations from Vessels Operating in the Antarctic Pack Ice Worby 1999 which provides an interactive tutorial and instructions for conducting ship based sea ice observations in the Antarctic The CD ROM also contains an image library and bibliography of sea ice types and general information on the role of sea ice in the global climate system ACCESS SOFTWARE AND RELATED FILES The software and related files described below have been specifically designed for conducting ship based observations of Antarctic sea ice and for entering quality controlling and processing the data The files are available via the ASPeCt Antarctic Sea Ice Processes and Climate program web site or on CD ROM Worby 1999 At the time of publication version 2 22 of the software was released Future upgrades will be available via the ASPECT web site at http www antcrc utas edu au aspect From this
63. ning in last hour sky discernible visibility 1000 43 Fog thinning in last hour sky not discernible visibility 1000 44 Fog unchanged in last hour sky discernible visibility 1000 45 Fog unchanged in last hour sky not discernible visibility 1000 46 Fog beginning thickening in last hour sky discernible visibility 1000 47 Fog beginning thickening in last hour sky not discernible visibility 1000 48 Fog depositing rime sky discernible visibility lt 1000 m 49 Fog depositing rime sky not discernible visibility 1000 Precipitation As Drizzle 50 59 50 Slight drizzle intermittent 51 Slight drizzle continuous 52 Moderate drizzle intermittent 53 Moderate drizzle continuous 54 Dense drizzle intermittent 55 Dense drizzle continuous 56 Freezing drizzle slight 57 Freezing drizzle moderate or dense 58 Drizzle and rain slight 59 Drizzle and rain moderate or dense Precipitation As Rain Not Showers 60 69 60 Slight rain intermittent 61 Slight rain continuous 62 Moderate rain intermittent 18 63 Moderate rain continuous 64 Heavy rain intermittent 65 Heavy rain continuous 66 Freezing rain slight 67 Freezing rain moderate or heavy 68 Rain drizzle and snow slight 69 Rain drizzle and snow moderate heavy Frozen Precipitation Not Showers 70 79 70 Slight fall of snow flakes intermittent 71 Slight fall of snow flakes cont
64. o Figure 2 4 Date gt gt To This specifies the last record of the file to be converted to text Pressing this button will display a dialog box with a list of records in the file Select the required record Refer to figure 2 4 28 Column Fields e Text File Preview Convert To Text File e Help Select Record Select Record Its Date Time Time Date 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 8 jun 1996 9 jun 1996 9 jun 1996 Figure 2 4 Select Date From To These are the fields that may be included in the destination text file To toggle between YES and NO click on the item After the text file is created it is displayed in this edit box A sample output is shown below Pressing this button will generate the text file Currently not implemented When you exit the dialog box the program will prompt you to save the setup configuration to the disk file seaice cfg This setup configuration is loaded each time the user opens the Convert to text file dialog box A typical text file is shown below showing the time date latitude longitude and primary ice conditions only Typical sample file output Rec Date Time Lat 1 4 aug 1997 13 00 64 933 2 4 aug 1997 20 00 65 033 3 4 aug 1997 2100 65 067 4 4 1997 22 00 65 100 5 4 aug 1997 2300 65 117 6 53091997 01 00
65. ol 3 2 Editing data The data set may be edited to exclude observations within a prescribed distance of the previous observation This is to prevent biasing in areas of heavy ice where the ship s speed is reduced The distance is usually set to 6 nautical miles corresponding to a straight line speed of 6 knots which most ice breakers are capable of maintaining in moderate pack ice The processing software enables the user to specify this distance orto use all observations regardless of spacing Observations are also removed when there is obvious biasing caused by the ship following easily navigable routes The most common example of this is near the ice edge when the ship may constantly pick its way through leads This is usually avoidable on voyages dedicated to sea ice research but may otherwise prove to be a problem Itis atthe discretion of the observer to either note that the data may be biased or not record data under such circumstances 3 3 Estimating the area averaged ice and snow thicknesses Estimates of the area averaged ice and snow thicknesses may be made over the ice covered region of the pack only or for the total pack ice zone including the open water fraction Each observation is equally weighted unless eliminated by the minimum distance rule described above For each hourly observation the estimated ice thickness values for each of the three dominant ice thickness categories are weighted by the ice concentration This provides a m
66. on 100 Note that if the file already exists the program will add the new records into the file Records are inserted into the file in chronological order If the file does not exist it will be created and will contain only the new records For Identical Records This drop list box is used to select from one of three update options If the destination log file already contains records with the same time and date as the old text file the user is given three options i Replace Replace all identical records found in the log file with the records from the fin and met files ii Don t Replace Don t replace the records iii Confirm Before Replacing Prompt before replacing each identical record Update Press this button to update the log file with the records from the fin and met files After completing the log file is shown in the list box All track distances are re calculated for the new log file 2 3 The RECORD Menu 2 3 1 Add New Record From the Record menu select the Add New Hecord function This menu function is used to add new observation records to the database log file and consists of three pages or sections of data General Ice Observation and Met Observation The dialog boxes for each section are shown in Figures 2 6 2 7 and 2 8 respectively When a new record is added to the file the record is inserted in chronological order by date and time All track distances are then automatically recalculated General This p
67. on the Plot Entire File button and the entire list will be highlighted If you wish to plot a subset of the file simply highlight the required observations in the list The marker style line thickness and line colour for a plot may be specified Note that there is an option to place a latitude and longitude marker at each observation point using the Mark each Location check box This box displays the latitude and longitude of the cursor in decimal degrees when the cursor is placed inside the plot region The cursor also changes to when inside the plot region This is a list box which displays the file name of all the database log files being plotted Each time a file is selected for plotting see the File button above the file name appears in this box Up to five log files may be plotted simultaneously If you click on a file name inside this list box that file and its plot options will appear on the screen and may be modified as described above 40 Load Plot File Ea C ALBEDO HIHOLAP1 LOG Square Figure 2 14 Load File Options 2 4 2 Plot Sea Ice Data Database files can be plotted as a time series plot From the Graphs menu select the Plot Sea Ice Data option and a blank graph will appear on the screen This plot facility allows any data either met or ice observation to be plotted versus time It also allows multiple y axis plots as shown in Figure 2 16 Note that only files may be plotted To plot a gr
68. ppear on the screen The details of all the sea ice calculations are described in the appendix Sea Ice Statistics Calculations Figure 2 20 Sea Ice Statistics 44 Load Discard Select ALL e Date FROM Date TO e Lat ALL e LAT From To e Lon ALL e LONG From To e Exclude Observations lt Sea Ice Statistics Specify the name of the database log file to process A file browser will appear on the screen similar to Figure 2 15 The file is loaded and the file name is displayed in the box to the left Note that multiple database files may be loaded and combined to give an overall statistical output To exclude a file from processing when multiple files are selected for processing simply click on the file name in the box to the left and hit the Discard button The file is then removed from the list of files to process The destination file name default is the same as the input file but with the extension sta The user may specify a different destination file name by clicking the Se ect button If this box is checked then the time and date is ignored in the processing If this box is not checked then the user must specify the Subset of records to be processed defined by a range of times and dates To specify the starting date of a subset of records for processing To specify the finishing date of a subset of records for processing If this box is checked then the latitude
69. rid Setup Figure 2 12 Grid Options 39 XY Plot Button Land Stations Button e File Button e Lat Lon Box e File List Box Currently not implemented A map of the Antarctic coastline can be plotted The dialog box in Figure 2 13 appears on the screen A file of 2000 latitude and longitude points called landmask map is supplied for this purpose Alternatively users may plot their own coastline data provided the input file consists of a series of latitude and longitude points in decimal degrees Adjacent points can be connected to produce a solid coastline by clicking on the Draw Solid Outline check box provided the data points are continuous around the continent which is not the case for the supplied landmask map file The location of most Antarctic stations may also be plotted on the map by clicking on the Show Stations check box Land Map File Plot it Land Map File Outline Color MEM Figure 2 13 Land Mask Options This button is used to load and plot a database log file The latitude and longitude of each observation will be plotted on the map The dialog box shown in Figure 2 14 will appear on the screen Clicking on the lt lt File button will enable the user to load a log file Each observation record in the file is listed along with the date time latitude and longitude of the observation To plot the entire file click
70. ries are based on WMO 1970 sea ice classifications First year ice greater than approximately 0 1 m thick is classified by its thickness e g young grey ice 0 1 0 15 first year ice 0 7 1 2 m while thinner ice is generally classified by type 0 frazil shuga grease and nilas A single category is defined for multi year ice There is also a category for brash which is common between floes in areas affected by swell and where pressure ridging has collapsed Books by e g Armstrong et al 1973 and Steffan 1986 and the CD ROM described on page ii Worby 1999 provide illustrated examples of different sea ice types 2 3 Ice Thickness 2 Ice thickness is estimated for each of the three dominant ice types It is helpful to the observer to suspend an inflatable buoy of known diameter or other gauge over the side of the ship approximately 1 m above the ice to provide a scaled reference against which floe thickness can be estimated The ice thickness can then be determined quite accurately as floes turn sideways along the ship s hull Only the thickness of level floes or the level ice between ridges is estimated This is because ridges tend to break apart into their component blocks when hit by the ship making it impossible to estimate their thickness In order to determine the thickness of ridged floes observations of the areal extent and mean sail height of the ridges are made see Section 2 5 and combined with the level ice th
71. rs oderate or heavy snow showers ight showers of soft or small hail oderate heavy showers of soft small hail ight showers of hail Moderate or heavy showers of hail x lt 50 50 200 200 500 500 1000 1 2 km 2 4 km 4 10 km gt 10 km Not available 61 3 7 Map Plotting Coordinate Transformation The map plotting facility described in section 2 4 1 Plot Ship Route is used to plot geographical maps and the location of the ship based ice observations on a polar stereographic plot of the southern hemisphere The latitude and longitude coordinates are mapped to pixel coordinates using the geodetic to polar stereographic projection Details of this algorithm can be found in Snyder 1982 Map projections used by the US Geological Survey US Geological Survey Bulletin 1532 The notation used is Re earth radius Sat standard latitude 70 00 earth eccentricity 0 081816154 polar stereographic coordinates latlon geodetic coordinates Sign 1 south pole radius of latitude circle on polar azimuthal projection or radius from centre on any azimuthal projection elipsoid correction factor 3 7 1 North or South Pole For the southern hemisphere a constant of 180 degrees XLAM is specified the northern hemisphere this value is 45 if lat 0 Sign 1 XLAM 180 lat 1xlat lon 1xlon else Sign 1 45 3 7 2 Calculate polar stereo
72. ssified using a three digit code between 500 and 897 The first digit 5 8 is a description of the type of ridge which may be unconsolidated consolidated or weathered This is determined from the appearance of the ridge and is useful for estimating ridge sail density The second digit 0 9 describes the areal coverage of ridges and the third digit 0 7 records the mean sail height to the nearest 0 5 These observations are probably the most subjective of those made from the ship and it is particularly important to standardise them between observers The observations of surface ridging are input to a model formulation as described in section 3 3 to estimate the mass of ice in ridges 2 6 Snow type s This is a descriptor for the state of the snow cover on sea ice floes It is important for estimating the area averaged albedo of the pack as discussed in Section 3 4 The snow classification is an integer between 0 and 10 For accurate Surface albedo calculations the snow cover classification describes the surface snow Hence in a case where fresh snow has fallen over older wind packed snow the classification code should describe the freshly fallen snow cover However it is very important that the total snow cover thickness is still recorded 2 7 Snow thickness sz An estimate of the snow cover thickness is made for each of the three dominant ice thickness categories Snow thickness is relatively straight forward to estimate for floes t
73. tion is the same This information is stored on the disk file seaice cfg Click on the Save to Disk button to save the configuration 48 2 6 2 Albedo Values From the Options menu select the Albedo Values option This menu function is used to view or change the sea ice albedo coefficients specified for each ice type and snow thickness These values are shown in Figure 2 22 Sea Ice Calculation Coefficients i E Ji oes ai 21 Young Grey ce 10 15em Young Grey First Year gt 120em CCICL m esa T Figure 2 22 Sea Ice Albedo Coefficients Any of the values may be changed however users should be aware that these values are based on results available from field experiments Allison et al 1993 S Warren personal communication 1998 The coefficients are used to calculate the area averaged albedo based on the observed distribution of ice types snow cover and open water within the pack ice The calculations are described in the appendix The coefficients are loaded from disk and stored on the disk file seaice cfg when changed The standard defaults are shown in Figure 2 22 The Load Factory Defaults button will change all the coefficients back to the original values Values are not specified for ice conditions that either do not occur or are unlikely to be observed These boxes are disabled and values can
74. to the East Antarctic pack since 1992 These data show that by incorporating the ridged ice the mean thickness increases by on average 1 7 times the observed mean undeformed ice thickness Individual voyages show increases of between 1 3 2 3 times 5 0 ACKNOWLEDGEMENTS The authors are grateful to Vicky Lytle and Rob Massom for their comments and input to the ice observation scheme Thanks also to Steve Ackley Martin J effries Christian Haas and Steve Warren who have trialed the observation scheme on numerous Antarctic voyages and provided valuable feedback Individual observers who have contributed to the success of the program over the past decade are too numerous to name individually the authors are grateful for the contributions of each one This publication has been produced in conjunction with the SCAR Global Change and the Antarctic GLOCHANT Antarctic Sea Ice Processes and Climate AS PeCt program 6 0 REFERENCES Ackley S F Mass balance aspects of Weddell Sea pack ice J Glaciol 24 90 391 405 1979 Allison E Brandt and 5 Warren East Antarctic sea ice albedo thickness distribution and snow cover J Geophys Res 98 C7 12 417 12 429 1993 Allison and Seasonal changes of sea ice characteristics off East Antarctica Ann Glaciol 20 195 201 1994 Armstrong T Roberts and Swithinbank Illustrated Glossary of Snow Ice Special Publication 4 60 pp Scott
75. um must also hold on the large scale however the effect of snow drifts around ridges may induce errors in both the observations and the model In particular observers may not be able to differentiate ridge sails from adjoining snow drifts hence the observations of the areal coverage and to a lesser extent height of ridging will include the fraction covered by snow This will affect the value r defined as the ratio of ice thickness below sea level to the combined thickness of ice and snow above sea level Hence the assumption that ridge sails are solid ice with a density of 900 kg m is incorrect and this is accounted for in the model To determine r in the vicinity of ridges data from drilled thickness transects that intersected ridges were examined Only transects or parts thereof with peaks in freeboard 20 5 m were considered and the mean ice and snow thicknesses were calculated A total of 339 drill holes from 9 thickness transects had mean ice and snow thicknesses of 1 18 m and 0 16 m respectively By assuming densities of 900 kg m and 360 kg m for ice and snow respectively the mean draft was calculated to be 1 12 m Hence 5 in areas of ridged ice The snow density value was derived from data collected on two voyages to the East Antarctic pack V9 92 93 and V1 95 96 with a mean value of 360 110 kg m over the range 120 760 kg In order to calculate only the thickness of ice in ridges it is necessary to remove the snow from the
76. umcoll y TypeCon k 1 sumcol2 x TypeCon k 2 sumcol3 x TypeCon k 3 sum sumcoll sumcol2 sumcol3 Average Ice Thickness total area Average Snow Thickness total area Average Albedo Total Ice Concentration Snow covered ice within pack Snow free ice within pack Open water within pack Percent snow covered ice Percent snow free ice Average ice thickness ice only Average snow thickness ice only Percent surface area ridged Average snow thickness snow only 3 2 Database log file Structure calculate column 1 sum k 1 to 10 calculate column 2 sum k 1 to 10 calculate column 3 sum k 1 to 10 SumAviceThickTot 10 N zSumAvSnoThickTot 10 N SumAvAlbedo 10 N 100 TypeCon 1 1 sumcol2 sumcol3 sumcoll TypeCon 1 1 TypeCon 1 1 100 sumcol2 sumcol3 sum TypeCon 1 1 2100 Percent snow covered ice 100 Average Ice Thickness Total Ice Conc 100 Average Snow Thickness Total Ice Conc SumP erAreaR idged 100 N Average Snow Thickness sumcol2 sumcol3 100 The database log file consists of binary records Each record consists of an ice observation record and met observation record The total size is 544 bytes per record When records are added to the log file they are inserted into the file chronologically and not necessarily appended to the end of the file Single Ice Classification primary secondary tertiary ice struct ICEOBS BOOL isValid
77. urned sideways along the ship s hull although at times the ice snow interface is difficult to distinguish particularly when the base of the snow layer has been flooded and snow ice has formed 2 8 Open water The codes for open water are descriptors for the size of the cracks or leads between floes not a concentration value in tenths As discussed above the length and breadth of the ship can act as a useful guide when estimating lead dimensions The ship s radar can also be useful particularly at night 2 9 Meteorological Observations Instantaneous conditions are usually recorded hourly but this may be reduced to three hourly The standard set of observations include water temperature air temperature true wind speed and direction total cloud cover visibility and current weather On most research vessels water temperature air temperature and wind speed and direction will be displayed on the bridge and may even be logged for the duration of the voyage Cloud cover can be estimated by the observer in eighths and visibility is estimated in kilometres from the ship Wind speed is recorded in ms and wind direction relative to north T The current weather is recorded using the Australian meteorological observer s two digit codes that are provided in appendix 3 Australian Bureau of Meteorology Only a subset of these codes pertinent to Antarctic conditions has been included in the software 2 10 Photographic Records During dayli
78. used for plotting the observation locations From the Graphs menu select Plot Ship Route option The dialog box shown in Figure 2 11 will appear on the screen The display consists of a polar stereographic projection of the south pole The latitude circles are labelled along the vertical and horizontal axes the longitude lines are labelled at the edges of the rectangular display region When the cursor 5 inside the plot region its coordinates are given in decimal latitude and longitude on the right of the scree Mapping and projection algorithms are given in the appendix Any part of the plot may be zoomed by clicking and dragging the mouse over the region to be enlarged The resulting enclosed area will be zoomed when the mouse is released You may also resize the dialog box simply by dragging the corners of the dialog box The dialog box contains the following controls Full Zoom Button Pressing this button will zoom out fully displaying the entire south polar region This is illustrated in Figure 2 11 Zoom Previous Button Adjusts plot to previous zoom coordinates Grid Button This controls the grid display i e the number of grid lines latitude and longitude increments colour etc A dialog box Figure 2 12 appears on the screen The grid can be turned on off and the latitude and longitude step size and colour can be changed 38 Plot Polar Figure 2 11 Graph Plot Plot Ship Route Display Polar G
79. wer resolution e 9 640 x 480 will work but are not as practical e 400 kbytes of disk space is required for the program as well as sufficient disk space for the data files Each hourly observation requires approximately 550 bytes of disk space 1 3 Installation To install the program create a subdirectory on the hard disk where the program will reside Then copy all the required files as described at the front of this report The program should be run from Windows 2 0 USER MANUAL 2 1 The main Screen Layout Running the program will produce a main screen which displays a table of daily sea ice observations The screen has a spreadsheet format similar to the proforma for the hand written observations This is illustrated in Figure 2 1 Note that all the fields are initially empty and that a log file must be loaded before it can be displayed The screen is divided into the following sections Menu Bar The individual menus are described in the next section Main titles Log file name Date and J ulian Day fields 25 Seaice Windows Application Seaice File Record Graphs e Five buttons e Title for data Table header Calculate Options Help Fi gure 2 1 The main window View Primary Ice View Secondary Ice View Tertiary Ice View Met Record and View Comments These buttons are used to display individual parts of the record This is shown in blue It indicates which field is currently displayed i e Pri
80. ype There may be times when only one or two different ice categories are present in which case only the primary or primary and secondary classifications are defined The observations are entered on log sheets using a standard set of codes based on the WMO 1970 nomenclature and designed exclusively for Antarctic sea ice A set of blank proformas is located in Appendix 1 and on the CD ROM described on page ii Examples of completed proformas are shown in Appendix 2 2 1 Ice Concentration c Total ice concentration is an estimate of the total area covered by all types of ice expressed in tenths and entered as an integer between 0 and 10 In regions of very high ice concentration 95 99 where only very small cracks are present the recorded value should be 10 and the open water classification should be 1 small cracks Regions of complete ice cover 10096 will be distinguished by recording an open water classification of 0 no openings An estimate of the concentration of each of the three dominant ice thickness categories is also made These values also expressed in tenths and should sum to the value of the total ice concentration It is sometimes difficult to divide the pack into three distinct categories and it may be necessary to group some categories together to ensure their representation 2 2 Ice Type ty The different ice categories together with the codes used to record the observations are shown in Table 2 1 The ice catego

Antarctic CRC Research Report 14 - Antarctic Sea Ice Processes

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