A COMPARISON OF CONVENTIONAL AND PASSIVE MICROWAVE SEA-ICE DATASETS FOR HUDSON-BAY

A sea-ice dataset derived from passive microwave data acquired by the Scanning Multichannel Microwave Radiometer (SMMR) is compared with a c onventional sea-ice dataset from Ice Branch, Atmospheric Environment S ervice, Canada. The conventional set uses data from several sources in cluding ships of opportunity, reconnaissance aircraft, satellite photo graphs and climate stations. The comparison was made for a 3-year peri od from 1979 to 1981 over Hudson Bay, an area that is covered with fir st-year ice only. For 8 of the 12 months of the year, monthly area-ave rage ice concentrations are within one tenth; larger differences are e vident during periods of melting and freeze-up. Extensive ponding on f irst-year ice during the melt season is interpreted as open water by t he SMMR algorithm, leading to significant ''errors'' in the passive mi crowave dataset. By comparing the two datasets, we were able to show t he extent of ponding on the ice for a complete seasonal melt cycle. Du ring freeze-up the algorithm, under some conditions, provides a better estimate of the amount of ice than a conventional dataset owing to th e difficulty of observing the presence of new ice.