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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.  

Rapid changes are occurring where the Antarctic ice sheet meets the ocean, particularly along the Antarctic Peninsula and in the Amundsen Sea.  This photo shows the ice shelf, or floating extension, of Pine Island Glacier, west Antarctica, one of the current "hotspots" of polar climate change (photo credit K. Leonard)
Snow cover is an important but poorly understood component of the Antarctic sea ice environment.  In contrast with the Arctic, there is very heavy snowfall over the Southern Ocean, which contributes to ice growth.  The heavy snow cover on Antarctic sea ice helps insulate the ice and ocean underneath from cold winter temperatures, and also influences biological processes in the upper ocean / sea ice environment.   (photo K. Leonard, Bellingshausen Sea, west 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.  

Observing the CTD instrument    
Katherine Leonard, observing the CTD instrument being lowered through a lead (natural opening) in the sea ice (photo credit Alain Hubert / IPF)

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.

Princess Elisabeth Station    
Princess Elisabeth Station, Antarctica (photo credit K. Leonard)