Fast-Ice Formation in Presence of Tabular Icebergs in McMurdo Sound, Antarctica

Icebergs calved from the Ross Ice Shelf during last five years (B15, C16 and C19) and currently adrift in the Ross Sea have had an impact on the formation and break-up of fast ice (sea ice that is immobile and attached to the shore) in the vicinity of McMurdo Sound. Between October 2004 and May 2005, a great wall of icebergs consisting of B15A, the Dragalski Ice Tongue, B15K and C16 fortuitously developed along the Victoria Land Coast and effectively isolated McMurdo Sound, from the effects of the open Ross Sea. During this time period, 40% to 90% of the seaward boundary of this area was blocked by these icebergs. The iceberg barrier occurred during the warmest summer months (December - March) when sea ice is normally cleared from the area; thus, as the 2005 austral winter progressed, land-fast multiyear sea ice has remained in the region, despite a subsequent break-down of the iceberg barrier (i.e., B15A drifting north). This barrier reduced the effect on the sea ice of southerly winds by presenting a mechanical buttress to nortward flow, and also blocked currents from the Ross Sea which normally contribute to the break up of fast ice in the austral summer. In addition, lateral melting of the icebergs resulted in the freshening of the ocean surface layer, enhancing stratification and sea-ice formation. This study shall Geographic Information System analysis of satellite imagery to quantify the length of the iceberg barrier, and to demonstrate the resultant impact on the development and total extent of fast ice. A simple numerical model of one-dimensional water-column/sea-ice interaction will be used to quantify the effects of fresh-water flux from iceberg melting and associated effects on sea-ice formation.