Sea-level Response to Ice Sheet Evolution

1. ? S e E a R S I Sea-level Response to Ice Sheet Evolution An IPCC-targeted study addressing “How large could the ice-sheet contribution to future sea level be ?” • Sea-level Response to Ice Sheet Evolution(SeaRISE) is a community organized effort to estimate the upper bound of ice sheet contributions to sea level in the next 100 to 200 years. • Objectives • develop a set of common input data • design and execute a set of numerical experiments employing a wide range ice sheet models • refine details of rapidly responding areas in particular experiments with ice stream/ice-shelf or ice-shelf/ocean regional models • publish results in time to inform the next report of the Intergovernmental Panel on Climate Change (IPCC) • Participating models will compare output to determine both the contribution to sea level and associated uncertainties. • Strategy • Whole ice sheet models lack internal processes responsible for recently observed change, thus these are prescribed externally and the models run to assess the evolving response to imposed forcing over the next 500 years. The prescriptions are intentionally extreme to assess the upper bound of possible ice sheet contributions to future sea level. • For reference, each model conducts two control runs: one with a constant climate and one with a climate matching the mean of coupled climate model results for the A1B1 scenario published in the IPCC Fourth Assessment Report. Results of any experiment are differenced from the control runs to quantify the sensitivity of the model to the prescribed forcing. The range of model responses is then examined to assess individual model behaviors. Standard data sets of many essential parameters are provided to minimize the differences between models. Sample Experiments Prescribed forcing experiments already undertaken include doubling sliding velocities of the Greenland ice sheet and melting of Antarctic ice shelves at rates of 2, 20 and 200 meters per year. Many other experiments are under consideration including retreat of grounding lines, basal lubrication tied to surface meltwaterproduction, and thawing of the subglacial bed. It is expected that regional models will not only refine ice sheet response in limited areas of high sensitivity but also help define additional external forcings. Community Participation in SeaRISE is voluntary and remains open. The guiding document is available on the web as a wiki (http://websrv.cs.umt.edu/isis/index.php/SeaRISE_Assessment) that is updated as community decisions are made and clarifications are required. Reports of SeaRISE activities are posted at http://oceans11.lanl.gov/trac/CISM/wiki/AssessmentGroup. Control simulation Extreme climate simulation Participating institutions: Hokkaido University Los Alamos National Laboratory NASA Goddard Space Flight Center NASA Jet Propulsion Laboratory New York University Pennsylvania State University Princeton University Universite Joseph Fourier University Corporation for Atmospheric Research University of Alaska-Fairbanks University of Bristol University of Buffalo University of California at Berkeley University of California at Santa Cruz University of Colorado University of Maine University of Maryland Baltimore County University of Montana University of Potsdam University of Texas at Austin University of Tokyo Additional participants are welcome; Contact: Robert.A.Bindschadler@nasa.gov