AN INTERCOMPARISON OF ANTARCTIC SEA-ICE EXTENT DATASETS FROM THE US-JOINT-ICE-CENTER (JIC) AND SATELLITE PASSIVE MICROWAVE OBSERVATIONS FOR1979-88

US Joint Ice Center (JIC) Antarctic sea ice extent data, the longest c ontinuous series of its kind for this part of the world, are compared with direct passive microwave-based estimates to assess their overall consistency both spatially and temporally in the period 1979-88. Using ice edge position as a proxy for ice extent, the comparison reveals c lose agreement in most years, in monthly averaged ice edge positions i n all Antarctic regions at the time of maximum ice extent, and also in autumn and spring in the Ross and Weddell Seas. Unexpectedly, JIC rel ative overestimation prevails during both autumn and spring in some ot her areas. Previously noted differences in JIG: and passive microwave total Antarctic extent in 1979-80 result mainly from problems in the R oss Sea. Reasons for the various discrepancies may lie in differences in the methods used to produce the datasets especially in spring but t hose in autumn seem to often arise for other reasons. It is found that the prevalent discrepancies in the Ross Sea in 1979-80 as well as tho se in spring in other regions from 1981 coincide with periods of ice e xtent change and the evolution/intensification of ice extent anomalies .