The Ob river releases large amounts of fresh water into the Kara Sea which freezes in the winter season. Some of this ice is landfast along the coasts as can be seen in the pair of ERS-1 SAR images from February 24 and 27, 1994 (see the location of the SAR image ). In this period southerly winds prevailed causing the drifting ice to move towards north.
The ice displacement is calculated from the two images using an ice kinematics algorithm and the velocity vectors are superimposed on top of the images. The mean displacement is 16 km in three days, which is equivalent to a mean ice speed of 6 cm/sec. The dark signature is thin new-frozen ice which has formed as the thicker pack ice moves towards north. Some of the ice in this region is freshwater ice, which is harder and more difficult to penetrate for the icebreakers compared with the saltier sea ice.

Legend:
A landfast ice
B island
C Yamal Peninsula

NERSC, Bergen, Norway

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry