Coastal sea ice variation around East Dronning Maud Land, Antarctica, during the last five decades
Abstract
Satellite images obtained in Lützow-Holm Bay (69ºS, 38ºE) have revealed frequent occurrences of ice-breakup events since the 1980s. Such unstable conditions continued for several to ten-odd years till now, and its variability coincides well with the characteristics of snow accumulation patterns on sea ice; in other words, breakups are often observed during periods of less snow. In contrast, during the 1950s 70s, landfast ice seems to have been extremely stable, judging from the appearance of a long glacier tongue (Shirase Glacier) flowing into the fast-ice field. The length of the tongue had reached ~75km as of 1980 just before the breakup and the equivalent time to its elongation has been estimated at about 30 years. Expansion and contraction of the floating ice tongue depends on its surrounding fast-ice condition. Then, the unstable sea-ice condition for the last two decades has shortened the ice tongue. A decrease in the snow cover on sea ice and warm periods of summer autumn led to the weakening of the landfast ice as the melt season progressed; broken floes were then transported offshore by the prevailing southerly winds. This is a possible scenario for the ice- breakup processes. Furthermore, characteristics of coastal ice variation are reflected in the navigation of the icebreaker, which has made a voyage almost at the same season (middle to late December) and in the same sailing route at the bay. The penetration distance by ramming icebreaking has negative correlation with ice/snow thicknesses and is regarded as an index for ice condition. The distances have shown distinct interannual variations; that is, the periods of longer distances coincide with those of frequent occurrence of breakup in mid-1980s and from late- 1990s to now, while short distances appeared in mid-1990s correspond with continuously stable ice condition without breakup.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.C52A..06U
- Keywords:
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- 0720 Glaciers;
- 0750 Sea ice (4540);
- 4207 Arctic and Antarctic oceanography (9310;
- 9315)