Monitoring of new-ice in Greenland waters

In the sea ice covered waters of Greenland the active polarisation ratio (APR) of QuikSCAT SeaWinds Ku-band (13 GHz) scatterometer measurements and the passive polarisation ratio (PPR) of DMSP-SSM/I 19 GHz radiometer measurements are used in combination to classify new-ice and older ice from 1999 to 2001. In particular, the two regions where new-ice is covering large areas: (1) Baffin Bay (64°W, 72°N) during the yearly freeze-up in autumn, and (2) the formation of the ´Odden´ in the Greenland Sea (8°W, 75°N) in late winter, were used in the study. The results of the surface cover classification in the Greenland Sea and in Baffin Bay were validated against 19 Radarsat ScanSAR wide scenes from the same period. In our study new-ice is defined according to its backscatter and radiative properties and our results show that the transformation to older ice usually occurs within one week. Further, the formation of new-ice and its transformation to older ice or the destruction of an ice cover occur on a daily time scale. The detection of new-ice using the above method is consistent with Radarsat data for areas >50 km both in Baffin Bay and the Greenland Sea. Furthermore, it was found that large areas are covered by new-ice during the freeze up of the Baffin Bay in October and November. In the Greenland Sea the new-ice appears in March as an ice peninsula appended to the belt of older ice drifting along the east coast of Greenland. These results have been confirmed by Radarsat observations. However the algorithm was found to mis-classify the surface cover in the following cases: (1) open water into sea ice at high surface wind speeds (>15 m/s), and (2) regions of grease ice into open water or other ice types.