Regional Classes of Sea Ice Cover in the East Antarctic Pack Observed from Satellite and In Situ Data during a Winter Time Period
Massom, RA and Comiso, JC and Worby, AP and Lytle, VI and Stock, L, Regional Classes of Sea Ice Cover in the East Antarctic Pack Observed from Satellite and In Situ Data during a Winter Time Period, Remote Sensing of Environment, 68, (1) pp. 61-76. ISSN 0034-4257 (1999) [Refereed Article]
Ice concentration data alone are often of limited use in many process, and modeling studies as different ice regimes of approximately 100% concentration can have significantly different heat flux, albedo, and other surface properties. Current ice concentration algorithms perform poorly in regions of predominantly thin or highly fragmented ice, which constitute a significant proportion of the pack in East Antarctica. The impact of the sea ice cover on high latitude air-sea interactions and marine ecology depends not only on ice extent and concentration but also on the ice-type composition of the pack. An unsupervised ice classification scheme, using data from four channels of the SSM/I, is presented and tested as a means of gaining important additional, complementary information on surface type. Class interpretation is by comparison with AVHRR, ERS-1 SAR, and near-coincident digital aerial photography and in situ data. The classification does a reasonable job at consistently differentiating the large-scale constituent regimes, including the outer marginal ice zone, the interior pack, and a transition zone separating the two. Given the short period of data analyzed, the cluster maps appear to be generally coherent and consistent through time as the pack changes in response to synoptic-scale atmospheric forcing, although the robustness of the technique needs further testing over longer time periods. An observed crossover in the meridional brightness temperature profiles is a dominant and consistent feature which marks the transition from unconsolidated and wet ice in the marginal ice zone to more consolidated ice with a thicker and drier snow cover in the interior pack. Ambiguities occur at the boundaries of some of these regimes due to sensor resolution limitations and the mixing of different ice types and open water. Also, some ice classes (like brash ice) cannot be distinguished from forming pancake ice. Furthermore, although the signature of the inner pack is usually distinct from that of the outer pack, we observed one extraordinary swell propagation event which led to ice fracturing and surface wetting, and significantly altered the surface classification. The results of this multiparameter study underline the importance of using multisensor systems synergistically to improve interpretation of passive microwave data and better characterize the complex Antarctic pack.