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01 March 2007

Global mapping of Arctic sea ice drift : a unique database

For several years, the CERSAT has been providing sea ice data and maps from various scatterometers (microwave radar) and radiometers onboard earth observation satellites (ERS-1, ERS-2, ADEOS-1, QuikSCAT, SSM/I, AMSR-E).

The scatterometer is initially designed to measure winds over ocean surface, but it can also be used to detect sea ice edge and sea ice type (first year, multi-year). Radiometer is commonly used for sea ice concentration. Using correlation technique between successive maps, sea ice drifts can be estimated from both of these sensors.

 IFREMER/CERSAT provides continuous Arctic sea ice drift maps from 1992, a unique database in the world.

From 1992 until 1999, 3 and 6 day-lags drifts are estimated from SSM/I radiometer. Since 1999, drifts are estimated from the combination of QuikSCAT scatterometer and SSM/I radiometer (merged drift), this product has been validated over 5 winters. Since 2002, AMSR-E radiometer provides higher resolution data, adapted to regional studies; due to its resolution, drifts can be estimated at 2 day-lag. Monthly merged drift maps are also available.

 

Figure 1 shows an example of 3 day-lag drift. Beaufort gyre and sea ice flux exit through Fram strait between Greenland and Spitzberg are sharply marked.

drift fig1 english largeArctic sea ice drift, 30th April-3rd May 2002, from the combination of SeaWinds/QuikSCAT scatterometer and SSM/I radiometer. Drifts less than one pixel are marked with a cross. In red : identical drift for QuikSCAT and the two SSM/I polarizations, in green : identical drift for two of the product ; in blue : selection of one product. Drifts are not estimated over grey areas. Blue areas are open-water areas. N.B. Vectors are not at the scale of the map.

 

 

 

drift fig2 largeFigure 2 : Arctic sea ice drift, 2nd-5th February 2005, from the combination of SeaWinds/QuikSCAT scatterometer and SSM/I radiometer. See caption of Figure 1.drift fig3 largeFigure 3 : Arctic sea ice drift, 2nd-5th February 2005, from AMSR-E radiometer. Drifts less than one pixel are marked with a cross. In red : identical drift for both polarizations (horizontal and vertical); in blue : selection of one product. Drifts are not estimated over grey areas. Blue areas are open ocean areas. N.B. Vectors are not at the scale of the map.

 

The comparison between merged (figure 2) and AMSR-E (figure 3) 3 day-lag drift maps shows that the higher resolution sensor AMSR-E provides drifts in coastal areas (canadian archipelago and North of Alaska). Angular resolution is also improved and drift vectors are more reliable but data gaps are visible, AMSR-E is thus well adapted to regional studies.

 

drift fig4 largeFigure 4 : Monthly Arctic sea ice drift, 1st-March-1st April 2005, from the combination of SeaWinds/QuikSCAT scatterometer and SSM/I radiometer. Drifts less than one pixel are marked with a cross. Drifts are not estimated over grey areas. N.B. Vectors are not at the scale of the map.

 

More information : ftp://ftp.ifremer.fr/ifremer/cersat/products/gridded/psi-drift/