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 : Arctic 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. |
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.
| Figure 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. |
) Figure 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.
Figure 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/