Sea‐ice conditions in the Ross Sea during spring 1996 as observed on SAR and AVHRR imagery

Abstract

The structure and properties of the sea‐ice field in the western Ross Sea during the spring of 1996 are evaluated using data from the ERS‐2 Synthetic Aperture Radar (SAR) and the Advanced Very High Resolution Radiometer (AVHRR) sensors. A multispectral classification method enabled separation of six ice types including fast ice, new ice, smooth first‐year ice, rough first‐year ice, thin new ice/wind roughened open water and glacial ice. In Terra Nova Bay it was observed that the size of the recurring polynya depended strongly on the strength of the consistent offshore winds arising from the strong katabatic wind flow down the Priestley and Reeves Glaciers. It appears that the presence and size of this feature is more dependent on atmospheric than on oceanographic forcing. The Terra Nova Bay Polynya is frequently not ice free, but covered, at least in part, by thin, new sea ice. During katabatic events, rows of new ice, formed in response to Langmuir circulations, are observed oriented perpendicular to the coastline. These structures are swept downstream where, under less turbulent conditions, they consolidate to form pancake ice and thicker icefloes. Elsewhere over the continental shelf sea‐ice conditions changed little in over a month, indicating that much of the ice in this area is landfast.