West Antarctic Ice Sheet Collapse Could Raise Sea Level 3 Meters

Summary: A study in Nov. 2's Proceedings of the National Academy of Sciences finds a 3-meter sea level rise from West Antarctic Ice Sheet collapse in 60 years.

Landsat Image Mosaic of Antarctica (LIMA): Public Domain, via NASA

Sixty years of sub-ice-shelf melting in the Amundsen Sea could be a tipping point for West Antarctic Ice Sheet collapse, yielding a global 3-meter (9.8 feet) sea level rise, suggests a study published Nov. 2, 2015, in the Proceedings of the National Academy of Sciences.

The study’s two co-authors, Johannes Feldmann and Anders Levermann, both with Germany’s Potsdam Institute for Climate Impact Research, note the significance of their findings as going beyond current short-term models to simulate a long-term scenario for the entire West Antarctic Ice Sheet (WAIS). Currently observed melting rates in the West Antarctic Ice Sheet’s Amundsen Sea account for a tipping point of ice-sheet instability after just 60 years. Sufficient -- not necessarily complete -- West Antarctic Ice Sheet collapse could slide the entire ice sheet into the ocean, where its displacement could affect sea levels in an unstoppable, long process lasting hundreds to thousands of years.

The authors explain: “Once the ice masses get perturbed, which is what is happening today, they respond in a non-linear way: there is a relatively sudden breakdown of stability after a long period during which little change can be found.”

The simulation’s long-term view considers tipping point implications for West Antarctica and for global coastlines. The Parallel Ice Sheet Model (PISM) used by the study’s authors suggests that ice loss in the Amundsen Sea sector then expands West Antarctica’s unfolding marine ice-sheet instability to the Filchner-Ronne Ice Shelf, on the southern shore of the Weddell Sea, and to Ross Ice Shelf, at the head of the Ross Sea. Tipping point-driven sea level rises lasting for an undetermined period of centuries to millennia call for long-term strategies for safeguarding global coastlines.

The authors conclude: “We thus might be witnessing the beginning of a period of self-sustained ice discharge from West Antarctica that requires long-term global adaptation of coastline protection.”

The topography of the Amundsen Sea area of the West Antarctic Ice Sheet is conducive to destabilization. The area’s downward, inland slope encourages sub-ice-shelf melting by channeling influxes of warm water to the ice sheet’s base.

The West Antarctic Ice Sheet receives its name from its location entirely within the Western Hemisphere. As Antarctica’s smaller, lower-lying portion, the ice sheet consists of a vulnerable, marine-based mass of glacier ice. The West Atlantic Ice Sheet lies on the South Pacific Ocean side of the Transantarctic Mountains, the range that divides the continent’s ice stream drainage between mainly Eastern and Western Hemisphere flows. Rising in sedimentary layers of coal, sandstone, and siltstone above a basement of granites and gneiss, the non-volcanic Transantarctic Mountains stretch lengthwise across Antarctica’s neck between West Antarctica’s Ross and Weddell seas and feature some noticeably ice-free peaks amid Antarctica's primarily icy, snowy panoramas.

The equation of ice with Antarctica, though, no longer seems a firm fact. “What we call the eternal ice of Antarctica unfortunately turns out not to be eternal at all,” says the study’s lead author, Johannes Feldmann.

Thwaites glacier in western Antarctica (AFP/Getty): Anders Levermann @ALevermann via Twitter Nov. 3, 2015

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Landsat Image Mosaic of Antarctica (LIMA): Public Domain, via NASA @ http://lima.nasa.gov/pdf/A3_overview.pdf

Thwaites glacier in western Antarctica (AFP/Getty): Anders Levermann‏ @ALevermann via Twitter Nov. 3, 2015, @ https://twitter.com/ALevermann/status/661457538383220737

For further information:

Anders Levermann‏ @ALevermann. "West-Antarctic-ice-sheet collapse follows local destabilization #sealevelrise @PIK_Climate." Twitter. Nov. 3, 2015.
Available @ https://twitter.com/ALevermann/status/661457538383220737

Carbon Brief. "Model simulation of loss of entire West Antarctic Ice Sheet." YouTube. Nov. 2, 2015.
Available @ https://www.youtube.com/watch?v=YJLSbYV2-zc

Feldmann, Johannes, and Anders Levermann. "Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin." Proceedings of the National Academy of Sciences of the United States of America, vol. 112, no. 46 (Nov. 17, 2015): 14191-14196.
Available @ http://www.pnas.org/content/early/2015/10/28/1512482112

PIK Press Office. "Local destabilization can cause complete loss of West Antarctica's ice masses." Potsdam Institute for Climate Change Research. Nov. 2, 2015.
Available @ https://www.pik-potsdam.de/news/press-releases/local-destabilization-can-cause-complete-loss-of-west-antarctica2019s-ice-masses