TO UNDERSTAND THE SEASONAL AND INTERSEASONAL VARIATION OF ICE TRANSPORT.

THE SPECIFIC WORK BEING CARRIED OUT IN THIS PROJECT FORMS PART OF A LARGER INTERNATIONAL STUDY THE GREENLAND SEA PROJECT OF THE ARTIC OCEAN SCIENCES BOARD.

THE CONTRACTOR HAS JUST RETURNED FROM AN ARTIC VOYAGE IN THE SUBMARINE HMS "SUPERB" , DURING WHICH ICE THICKNESS ALONG THE TRACK WITH AN UPWARD-LOOKING SONAR, AND ICE ROUGHNESS CHARACTERISTICS WITH A SIDESCAN SONAR WERE MEASURED. TWO AIRCRAFT COLLABORATED IN THE EXPERIMENT BY FLYING ALONG THE SAME TRACK AS THE SUBMARINE OBTAINING IMAGERY USING SAR ( SYNTHETIC APERTURE RADAR ) AND PASSIVE MICROWAVE. THE FUNDS REQUESTED ARE FOR THE PURPOSE OF SUPPORTING TWO STUDENTS AND A RESEARCH ASSISTANT WHO WILL HELP IN THE EFFICIENT AND RAPID PROCESSING OF THESE DATA. IN ADDITION, A SECOND SUBMARINE EXPEDITION TO THE ARTIC WILL BE UNDERTAKEN IN THE SAME SEASON (MAY) OF 1988 USING TWO SUBMARINES, GIVING THE OPPORTUNITY TO COMPARE THE ICE THICKNESS CHARACTERISTICS IN TWO SUCCESSIVE YEARS.

THE SUBMARINE DATA GIVE THE ICE THICKNESS DITRIBUTION VERY EXACTLY, BUT ONLY, OF COURSE, ALONG THE SUBMARINE TRACK. NO REMOTE SENSING TECHNIQUE GIVES ICE THICKNESS DIRECTLY, BUT WE WILL USE THE SUBMARINE DATA TO CALIBRATE PASSIVE MICROWAVE SENSORS AND THUS OBTAIN THE THICKNESS DISTRIBUTION INDIRECTLY. THE METHOD IS AS FOLLOWS. THE TRACK OF "SUPERB" WAS COVERED DURING HER VOYAGE BY A P-3 AIRCRAFT OF NASA EQUIPPED WITH PASSIVE MICROWAVE RADIOMETERS OF THE SAME FREQUENCIES AS THE SENSORS USED IN THE SSM/I (SPECIAL SENSOR MICROWAVE IMAGER) ON THE DMSP SATELLITE (SUCCESSOR TO NIMBUS-7). EXISTING ALGORITHMS YIELD TOTAL ICE CONCENTRATION A AND MULTI-YEAR ICE FRACTION F FROM THE BRIGHTNESS TEMPERATURES PERCEIVED AT THESE FOUR FREQUENCIES. THE AIRCRAFT/SUBMARINE DATA WILL YIELD ICE THICKNESS CORRESPONDING TO DIFFERENT BRIGHTNESS TEMPERATURES AT THE SAME FREQUENCIES. IT SHOULD THEREFORE BE POSSIBLE TO ASSOCIATE A MEAN ICE THICKNESS WITH EACH BRIGHTNESS TEMPERARURE AND THUS DRAW UP CALIBRATION CURVES TO DERIVE MEAN ICE THICKNESS OR EVEN THICKNESS DISTRIBUTION FROM A AND F . THIS IS THEN BE APPLIED TO THE SSM/I DATA FROM THE GREENLAND SEA AND FRAM STRAIT AS A WAY OF MEASURING VARIATIONS IN ICE VOLUME OVER LARGE AREAS.

TO CONVERT THESE THICKNESS DISTRIBUTIONS INTO TRANSPORT ESTIMATES WE NEED ICE VELOCITY. WE WILL USE CONCURRENT SATELLITE IMAGERY AT HIGH RESOLUTION (LANDSAT AND SPOT) AND LOW RESOLUTION (NOAA AVHRR) AND SUPERIMPOSE SUCCESSIVE IMAGES TO OBTAIN ICE DRIFT VECTORS. USE WILL ALSO MADE OF DATA FROM ARGOS DRIFTING BUOYS (FRENCH,US,NORWEGIAN) AND CURRENT METER STRINGS, NOTABLY THE GERMAN SET OF MOORINGS INSTALLED AT 79 N IN APRIL 1987.