Probabilistic framework for assessing the ice sheet contribution to sea level change

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 9; pp. 3264 - 3269
• Main Authors: Little, Christopher M., Urban, Nathan M., Oppenheimer, Michael
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences 26.02.2013; National Acad Sciences
• Subjects: Antarctic Regions; Basins; Climate Change; Climate change adaptation; Climate models; Correlation analysis; Earth, ocean, space; Exact sciences and technology; External geophysics; Glaciers; Ice; Ice Cover; Ice sheets; Mass balance; Oceans and Seas; Physical Sciences; Physics of the oceans; Probability; Probability distribution; Sea level; Sea level rise; Snow. Ice. Glaciers; Social Sciences; Surface waves, tides and sea level. Seiches; Uncertainty; Antarctica; Greenland; polar regions; Antarctic Regions; glaciology; risk management; Century 21st; Probabilistic approach; mass balance; Cryosphere ocean interaction; Decision making; Glacier variation; Sea level rise; Climate prediction; ice sheets; decision-making; Risk assessment; Polar region; sea level; climate change; Glacier dynamics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1214457110

Previous sea level rise (SLR) assessments have excluded the potential for dynamic ice loss over much of Greenland and Antarctica, and recently proposed “upper bounds” on Antarctica’s 21st-century SLR contribution are derived principally from regions where present-day mass loss is concentrated (basin 15, or B15, drained largely by Pine Island, Thwaites, and Smith glaciers). Here, we present a probabilistic framework for assessing the ice sheet contribution to sea level change that explicitly accounts for mass balance uncertainty over an entire ice sheet. Applying this framework to Antarctica, we find that ongoing mass imbalances in non-B15 basins give an SLR contribution by 2100 that: (i) is comparable to projected changes in B15 discharge and Antarctica’s surface mass balance, and (ii) varies widely depending on the subset of basins and observational dataset used in projections. Increases in discharge uncertainty, or decreases in the exceedance probability used to define an upper bound, increase the fractional contribution of non-B15 basins; even weak spatial correlations in future discharge growth rates markedly enhance this sensitivity. Although these projections rely on poorly constrained statistical parameters, they may be updated with observations and/or models at many spatial scales, facilitating a more comprehensive account of uncertainty that, if implemented, will improve future assessments.