Warm Ocean Water Melting Antarctic Ice Shelves from Below
26.04.2012 - Atmosphere & Space, Water & Oceans, Ice & Snow, Antarctic
Results of a new multinational study published in Nature show that warming ocean water making itw way under ice shelves in Antarctica is a major cause of ice loss on the continent. Carried out by researchers from the British Antarctic Survey, Utrecht University, the University of California San Diego and the non-profit Earth and Space Research institute.
Taking a time series of 4.5 million surface height measurements using a laser mounted on NASA’s Ice, Cloud and land Elevation Satellite (ICESat), the team of researchers was able to measure the thinning taking place on the ice shelves around the coast of Antarctica. Their results indicate that melting can be attributed not only to warmer air above, but to warmer ocean currents below the ice tongues.
Ice tongues form when glaciers draining ice from the interior of the continent move out over the sea and form a tongue of ice that floats on the water. Normally icebergs calve off at the end of the ice tongue as new ice moves in from the interior of the ice sheet to replace it.
However the warmer waters below the ice tongues are thinning and weakening them, causing them to lose ice more quickly. This in turn allows the rate at which ice flows into the ice tongues from outlet glaciers to accelerate, causing more ice to be drained from the interior of the ice sheet and contributing to sea level rise.
Researchers say that the ice loss caused by warmer waters is the most widespread and rapid in West Antarctica and most of the Antarctic Ice Sheet loss during the period covered under the study, between October 2003 and October 2008.
Dr. Hamish Pritchard from the British Antarctic Survey (BAS), lead author of the study, stated that “We can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt…The oceans can do all the work from below.”
The team was also able to determine how changes in wind patterns brought about by climate change have contributed to warming oceans. Altered wind patterns have been affecting the direction of ocean currents, causing warmer water to be directed under the ice tongues along the coast of Antarctica.
Measurements taken using a laser can deliver more precise changes in ice thickness. ICESat measured how ice shelf height changed over time and compared it to computer models - taking into account changes from natural snow accumulation and compaction as well as height changes caused by high and low tides.