On iceberg behaviour : observations , model results and satellite data

Abstract

Iceberg calving events from the Antarctic ice shelves occur on a regular basis and amount to about 2000 Gt/a (Jacobs et al., 1992). Large tabular icebergs originate in the Weddell and Ross seas from the Filchner-Ronne and Ross Ice Shelves. Smaller sized icebergs with length of the order of one kilometer or less might contribute an equal amount of freshwater to the Southern Ocean. Gladstone et al. (2001) suggest a freshwater input of 410 Gt/a for the Weddell Sea. Iceberg motion determines where the fresh water fromthe Anatrctic continent is supplied to the ocean. As part of the freshwater budget, like precipitation minus evaporation or differential freezing and melting of sea ice, the fate of icebergs might locally effect the stability of the water column with consequences for the formation of deep and bottomwater and the biology of the surface mixed layer. Some questions are: • Where do smaller/mediumsized icebergs drift? • What is the influence of sea-ice on iceberg drift pattern? • Where are the areas ofmajor freshwater contributions? • What is the quantity of freshwater input frommelting? and • What are the effects of iceberg melting on biological productivity? This study addresses the questions by combining a) direct observations, i.e. icebergs tagged with GPS sensors, b) an iceberg drift modell, and c) SeaWiFS data.