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Projecting Antarctica's contribution to future sea level rise from basal ice shelf melt using linear response functions of 16 ice sheet models (LARMIP-2)

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Title: Projecting Antarctica's contribution to future sea level rise from basal ice shelf melt using linear response functions of 16 ice sheet models (LARMIP-2)
Authors: Levermann, Anders Browse this author
Winkelmann, Ricarda Browse this author
Albrecht, Torsten Browse this author
Goelzer, Heiko Browse this author
Golledge, Nicholas R Browse this author
Greve, Ralf Browse this author →KAKEN DB
Huybrechts, Philippe Browse this author
Jordan, Jim Browse this author
Leguy, Gunter Browse this author
Martin, Daniel Browse this author
Morlighem, Mathieu Browse this author
Pattyn, Frank Browse this author
Pollard, David Browse this author
Quiquet, Aurelien Browse this author
Rodehacke, Christian Browse this author
Seroussi, Helene Browse this author
Sutter, Johannes Browse this author
Zhang, Tong Browse this author
Van Breedam, Jonas Browse this author
Calov, Reinhard Browse this author
DeConto, Robert Browse this author
Dumas, Christophe Browse this author
Garbe, Julius Browse this author
Gudmundsson, G. Hilmar Browse this author
Hoffman, Matthew J Browse this author
Humbert, Angelika Browse this author
Kleiner, Thomas Browse this author
Lipscomb, William H Browse this author
Meinshausen, Malte Browse this author
Ng, Esmond Browse this author
Nowicki, Sophie M. J Browse this author
Perego, Mauro Browse this author
Price, Stephen F Browse this author
Saito, Fuyuki Browse this author
Schlegel, Nicole-Jeanne Browse this author
Sun, Sainan Browse this author
van de Wal, Roderik S. W Browse this author
Issue Date: 14-Feb-2020
Journal Title: Earth System Dynamics
Volume: 11
Issue: 1
Start Page: 35
End Page: 76
Publisher DOI: 10.5194/esd-11-35-2020
Abstract: The sea level contribution of the Antarctic ice sheet constitutes a large uncertainty in future sea level projections. Here we apply a linear response theory approach to 16 state-of-the-art ice sheet models to estimate the Antarctic ice sheet contribution from basal ice shelf melting within the 21st century. The purpose of this computation is to estimate the uncertainty of Antarctica's future contribution to global sea level rise that arises from large uncertainty in the oceanic forcing and the associated ice shelf melting. Ice shelf melting is considered to be a major if not the largest perturbation of the ice sheet's flow into the ocean. However, by computing only the sea level contribution in response to ice shelf melting, our study is neglecting a number of processes such as surface-mass-balance-related contributions. In assuming linear response theory, we are able to capture complex temporal responses of the ice sheets, but we neglect any self-dampening or self-amplifying processes. This is particularly relevant in situations in which an instability is dominating the ice loss. The results obtained here are thus relevant, in particular wherever the ice loss is dominated by the forcing as opposed to an internal instability, for example in strong ocean warming scenarios. In order to allow for comparison the methodology was chosen to be exactly the same as in an earlier study (Levermann et al., 2014) but with 16 instead of 5 ice sheet models. We include uncertainty in the atmospheric warming response to carbon emissions (full range of CMIP5 climate model sensitivities), uncertainty in the oceanic transport to the Southern Ocean (obtained from the time-delayed and scaled oceanic subsurface warming in CMIP5 models in relation to the global mean surface warming), and the observed range of responses of basal ice shelf melting to oceanic warming outside the ice shelf cavity. This uncertainty in basal ice shelf melting is then convoluted with the linear response functions of each of the 16 ice sheet models to obtain the ice flow response to the individual global warming path. The model median for the observational period from 1992 to 2017 of the ice loss due to basal ice shelf melting is 10.2 mm, with a likely range between 5.2 and 21.3 mm. For the same period the Antarctic ice sheet lost mass equivalent to 7.4 mm of global sea level rise, with a standard deviation of 3.7 mm (Shepherd et al., 2018) including all processes, especially surface-mass-balance changes. For the unabated warming path, Representative Concentration Pathway 8.5 (RCP8.5), we obtain a median contribution of the Antarctic ice sheet to global mean sea level rise from basal ice shelf melting within the 21st century of 17 cm, with a likely range (66th percentile around the mean) between 9 and 36 cm and a very likely range (90th percentile around the mean) between 6 and 58 cm. For the RCP2.6 warming path, which will keep the global mean temperature below 2 ∘C of global warming and is thus consistent with the Paris Climate Agreement, the procedure yields a median of 13 cm of global mean sea level contribution. The likely range for the RCP2.6 scenario is between 7 and 24 cm, and the very likely range is between 4 and 37 cm. The structural uncertainties in the method do not allow for an interpretation of any higher uncertainty percentiles. We provide projections for the five Antarctic regions and for each model and each scenario separately. The rate of sea level contribution is highest under the RCP8.5 scenario. The maximum within the 21st century of the median value is 4 cm per decade, with a likely range between 2 and 9 cm per decade and a very likely range between 1 and 14 cm per decade.
Type: article
Appears in Collections:低温科学研究所 (Institute of Low Temperature Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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