Antarctic Seals and the Sea-ice EnvironmenT (ASSET)

Given the sensitivity of the sea-ice zone to global warming (IPCC 2013), there is an urgent need for determining how top predators use their physical and biological environment, in order to understand and predict their response to climate change in the different Antarctic regions. Events such as calving of large icebergs provide a framework for natural experiments to study the consequences of habitat variations on higher trophic level populations. Because the occurrence of such extreme events around Antarctica is predicted to increase due to global warming, it is now timely to study the ecological response of higher trophic levels to calving of large icebergs and their oceanographic consequences. We propose to take advantage of the unique opportunity offered by the recent Mertz Glacier Tongue calving in Adélie Land (Feb. 2010) to continue an unprecedented time-series on the winter foraging movements and in-situ oceanographic conditions of an ice-dependent top predator, the Weddell seal, spanning over 13 years and encompassing this significant climate event. Using vertical T/S/chlorophyll profiles collected by the seals during their dives in winter, we will link their foraging behaviour to in situ hydrographic conditions before and after the Mertz Glacier calving, and assess impact of the Mertz Glacier calving on ocean/sea ice interactions and primary production in the Dumont d’Urville region, and their potential consequences on the seals foraging behaviour. We will also complete our time-series on the foraging ecology of Weddell seals during summer (post breeding), during which ice retreat stimulates primary production. Finally, we propose to develop new seal-borne sensors to measure otherwise poorly sampled key sea-ice parameters such as sea-ice thickness and sea-ice algae biomass. By so doing, we will simultaneously address urgent questions on upper trophic levels ecology, primary production processes in and below sea-ice, and sea-ice/ocean interactions in an innovative and cost-efficient way.