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Water properties in the antarctic
The Antarctic ice sheet gains mass through snowfall, and loses
it through a variety of processes.Through this project, we aim to quantify many of these processes.
Dr. Katherine Leonard of the SLF snow-cover and micro-meteorology group and the EPFL CRYOS Lab led a scientific expedition to the Roi Baudoin ice shelf on the Princess Ragnhild Coast of east Antarctica in November - December 2011. This project was part of the Belgian Science Policy Office (BELSPO) - funded "BELISSIMA" project, which seeks to understand ice shelf and sea ice mass balance processes in this region of East Antarctica.
The focus of this year's expedition was to measure the water properties at the boundary between the ice shelf and the Southern Ocean. The Antarctic ice sheet gains mass through snowfall, and loses it through a variety of processes. Melting occurs where ocean water that is warmer than the in-situ freezing point (about -1.8 C) comes into contact with the bottoms of ice shelves and at ice sheet grounding lines (the zone where the ice sheet changes from sitting on bedrock to floating on the ocean). The earth's oceans are warming, and this trend is particularly strong in the Southern Ocean offshore from Antarctica. In places where this warm water is able to reach the ice sheet, melt is occurring, which is causing the inland ice to move more rapidly towards the ocean.
The oceanographic measurements were made using an acoustic depth sounder, to determine the water depth, and a "CTD" (conductivity - temperature - depth) instrument, that recorded the temperature, salinity, dissolved oxygen content, and turbidity of the water several times per second as the instrument was lowered to the ocean floor and brought back to the surface.
These measurements are traditionally made from ice-breaking research ships, but in this case the expedition traveled from Princess Elisabeth Station to the coast in tractors, and used skidoos to transport the researchers and equipment onto the sea ice (floating frozen ocean water). The measurements were made through holes drilled in the ice and in leads, natural breaks in the sea ice. In combination with the oceanographic measurements, the team collected data on the sea ice and the properties of its snow cover.