Future of the West Antarctic Ice Sheet

West Antarctic Ice Sheet and Climate Change – a Polar Puzzle

The West Antarctic Ice Sheet (WAIS) is one of the key polar scientific puzzles for projecting the consequences of climate change. WAIS holds a potential 11-20 feet (3.3-6 meters) of global sea level rise and is inherently unstable because it is grounded on rock that lies well below sea level. Little is known about the dynamics and potential for a rapid disintegration (or collapse) of WAIS, whereby the ice sheet could flow at increasing rates into the ocean as the ice shelves that protect it from the encroaching oceans diminish. However, recent research appears to indicate that WAIS is changing more rapidly than was previously thought.

The Antarctic Ice Sheets are losing mass, and this loss is accelerating

The use of gravity measurements coupled with general satellite observations of the Earth’s ice sheets, confirm that the Antarctic and Greenland Ice Sheets are losing mass, and that this loss has been accelerating over the past 18 years.

Changes to WAIS are happening now and are related to anthropogenic climate change

Ice shelves form over the water and serve as buttresses for the inland ice sheets behind them. Not all ice shelves are thinning, but those that are, are melting on their undersides, a process called basal melting. The highest thinning rates occur where the ice shelves interact with the warmest sea water, which is influenced by wind forcing, ocean upwelling, and atmospheric warming.

New research has shown that not only the Antarctic Peninsula but also West Antarctica is warming and that human effects may be playing a significant role in these changes. As the air warms and atmospheric circulations intensify, changes to the ice are expected to occur. For example, the previously stagnant, Kamb Ice Stream in the Ross Sea sector of WAIS may return to flowing sometime this century, rapidly increasing the WAIS contribution to global sea level.

WAIS is likely to survive mostly intact for this century, but a “collapse,” if and when it happens, will raise sea level by 10 feet (3 meters)

While these changes are happening now, WAIS seems likely to remain stable in the short term. Experts do not agree on the likelihood nor rate of a rapid WAIS disintegration, however, the expected sea level rise generated would create profound impacts on global infrastructure and society.

A West Antarctic Tipping Point threshold is likely to exist, though the science is not settled

Is there a temperature threshold which, when crossed, forms the “point of no return” for WAIS disintegration? The notion of a tipping point is compelling because it provides a specific target to avoid, in order to keep WAIS stable for now. However, it is important to note that there may be more complexity involved in “tipping” the ice sheet into disintegration, including temperature changes, oceanic changes, and the internal behavior of the ice sheet.

The article above is based on an Information Paper presented by the Antarctic and Southern Ocean Coalition (ASOC) at the 36th Antarctic Treaty Consultative Meeting held recently in Brussels. (See attachment below). The 5th Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), due in 2014, will provide the latest scientific knowledge on the future for WAIS.

Header image: www.antarcticglaciers.org

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