Coast News

Antarctica Remains the Wild Card for Sea-Level Rise Estimates Through 2100

Comprehensive sea-level rise projections

TOP0505AntarcticIceFlowPresent day Antarctic ice flow as simulated by the MALI ice sheet model (jointly developed by Los Alamos and Sandia national laboratories, and simulation image by John Patchett of LANL). Interior grey-to-white areas indicate slow flowing regions while warmer colored areas indicate faster flowing regions (dark red ~10 meters/day). Large orange-to-red regions near the ice sheet margins are floating ice shelves. Fine lines indicate the path of ice flow from the interior, through outlet glaciers and ice streams, and into fringing ice shelves.

A massive collaborative research project covered in the journal Nature this week offers projections to the year 2100 of future sea-level rise from all sources of land ice, offering the most complete projections created to date.

"This work synthesizes improvements over the last decade in climate models, ice sheet and glacier models, and estimates of future greenhouse gas emissions," said Stephen Price, one of the Los Alamos scientists on the project. "More than 85 researchers from various disciplines, including our team at Los Alamos National Laboratory, produced sea-level rise projections based on the most recent computer models developed within the scientific community and updated scenarios of future greenhouse gas emissions," said Price.

The estimates show that limiting global warming to 1.5 degrees C above pre-industrial temperatures would cut projected 21st century sea-level rise from land ice in half, relative to currently pledged emissions reductions. For example, the paper notes that, when looking at all land ice sources, the median projection of cumulative rise in sea level by the year 2100 decreases from approximately 25 cm to approximately 13 cm when emissions are limited.

The term "land ice" includes mountain glaciers such as those in Alaska, Europe, high-mountain Asia, etc.; ice caps including those of Iceland and the Canadian Arctic; and ice sheets in Greenland and Antarctica.

Continental Wild Card

Interestingly, Price points out, Antarctica continues to be the wild card. "Future changes to Antarctica remain highly uncertain," he said. "Because of this, our high-end estimates for sea-level rise from land ice are more than twice as large as the 'most likely' estimate." This is largely due to substantial uncertainty in how strongly warm ocean waters erode floating parts of the ice sheet from beneath.

Apart from that uncertainty, the bulk of the Antarctic sea-level rise projections do not show a strong sensitivity to different emissions scenarios, but a small number of projections result in an up to five-fold increase in sea-level contribution, Price said. Indeed, improving DOE's ability to accurately simulate Southern Hemisphere climate and Antarctic ice sheet evolution has been a focus of Los Alamos efforts for more than a decade.

By DOE/Los Alamos National Laboratory

Journal Reference

Tamsin L. Edwards, Sophie Nowicki, Ben Marzeion, Regine Hock, Heiko Goelzer, Hélène Seroussi, Nicolas C. Jourdain, Donald A. Slater, Fiona E. Turner, Christopher J. Smith, Christine M. McKenna, Erika Simon, Ayako Abe-Ouchi, Jonathan M. Gregory, Eric Larour, William H. Lipscomb, Antony J. Payne, Andrew Shepherd, Cécile Agosta, Patrick Alexander, Torsten Albrecht, Brian Anderson, Xylar Asay-Davis, Andy Aschwanden, Alice Barthel, Andrew Bliss, Reinhard Calov, Christopher Chambers, Nicolas Champollion, Youngmin Choi, Richard Cullather, Joshua Cuzzone, Christophe Dumas, Denis Felikson, Xavier Fettweis, Koji Fujita, Benjamin K. Galton-Fenzi, Rupert Gladstone, Nicholas R. Golledge, Ralf Greve, Tore Hattermann, Matthew J. Hoffman, Angelika Humbert, Matthias Huss, Philippe Huybrechts, Walter Immerzeel, Thomas Kleiner, Philip Kraaijenbrink, Sébastien Le clec’h, Victoria Lee, Gunter R. Leguy, Christopher M. Little, Daniel P. Lowry, Jan-Hendrik Malles, Daniel F. Martin, Fabien Maussion, Mathieu Morlighem, James F. O’Neill, Isabel Nias, Frank Pattyn, Tyler Pelle, Stephen F. Price, Aurélien Quiquet, Valentina Radić, Ronja Reese, David R. Rounce, Martin Rückamp, Akiko Sakai, Courtney Shafer, Nicole-Jeanne Schlegel, Sarah Shannon, Robin S. Smith, Fiammetta Straneo, Sainan Sun, Lev Tarasov, Luke D. Trusel, Jonas Van Breedam, Roderik van de Wal, Michiel van den Broeke, Ricarda Winkelmann, Harry Zekollari, Chen Zhao, Tong Zhang, Thomas Zwinger. Projected land ice contributions to twenty-first-century sea level riseNature, 2021; 593 (7857): 74 DOI: 10.1038/s41586-021-03302-y

Funding was provided by the DOE Office of Science, from the offices of Biological and Environmental Research (BER) and Advanced Scientific Computing Research (ASCR).

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