Rapid development and persistence of a massive Antarctic sea ice tongue

Abstract

An extraordinary sea ice tongue developed near 85°E over a period of 30 days in April-May 2002. The ice tongue extended to the north more than 800 km from the surrounding ice edge and covered an area greater than 200,000 km2. Satellite measurements of ice extent and roughness characteristics demonstrate that the tongue persisted as a distinct feature throughout the winter. Remote sensing observations between 1978 and 2004 confirm that ice tongues occur frequently at this location, although the 2002 tongue was particularly pronounced. We show that ocean currents and winds conspire to favor the development of ice tongues at this location. Mean streamlines of the southern part of the Antarctic Circumpolar Current turn sharply to the north near 85°E after passing through the Princess Elisabeth Trough. The edge and northern limit of the ice tongue correspond well with the pattern of mean streamlines. Mean winds in April-May have a dominant southerly component in this location, favoring offshore advection of ice; year-to-year variability in the prominence of the tongue is largely caused by variations in the wind, with northerly (southerly) anomalies inhibiting (promoting) development of a sea ice tongue. Ice drift is strongly northward along the axis of the tongue, suggesting the feature is formed by advection of ice from the south rather than by in situ thermodynamic ice formation. The northward current and sea ice tongue at 85°E are associated with higher biomass at all trophic levels than observed elsewhere in east Antarctica. Copyright 2008 by the American Geophysical Union.