Shear-margin melting causes stronger transient ice discharge than ice-stream melting in idealized simulations

Feldmann, Johannes, Reese, Ronja, Winkelmann, Ricarda and Levermann, Anders (2022) Shear-margin melting causes stronger transient ice discharge than ice-stream melting in idealized simulations. The Cryosphere, 16 (5). pp. 1927-1940. ISSN 1994-0424

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Basal ice-shelf melting is the key driver of Antarctica's increasing sea-level contribution. In diminishing the buttressing force of the ice shelves that fringe the ice sheet, the melting increases the ice discharge into the ocean. Here we contrast the influence of basal melting in two different ice-shelf regions on the time-dependent response of an isothermal, inherently buttressed ice-sheet-shelf system. In the idealized numerical simulations, the basal-melt perturbations are applied close to the grounding line in the ice-shelf's (1) ice-stream region, where the ice shelf is fed by the fastest ice masses that stream through the upstream bed trough and (2) shear margins, where the ice flow is slower. The results show that melting below one or both of the shear margins can cause a decadal to centennial increase in ice discharge that is more than twice as large compared to a similar perturbation in the ice-stream region. We attribute this to the fact that melt-induced ice-shelf thinning in the central grounding-line region is attenuated very effectively by the fast flow of the central ice stream. In contrast, the much slower ice dynamics in the lateral shear margins of the ice shelf facilitate sustained ice-shelf thinning and thereby foster buttressing reduction. Regardless of the melt location, a higher melt concentration toward the grounding line generally goes along with a stronger response. Our results highlight the vulnerability of outlet glaciers to basal melting in stagnant, buttressing-relevant ice-shelf regions, a mechanism that may gain importance under future global warming.

Item Type: Article
Additional Information: Funding Information: Johannes Feldmann acknowledges support by the priority program “Antarctic Research with comparative investigations in Arctic ice areas” SPP 1158 through grant WI 4556/6-1. Ronja Reese and Ricarda Winkelmann are grateful for support by the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 820575 (TiPACCs). Ricarda Winkelmann further acknowledges support by the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 869304 (PROTECT). Development of PISM is supported by NASA grant NNX17AG65G and NSF grants PLR-1603799 and PLR-1644277. The authors gratefully acknowledge the European Regional Development Fund (ERDF), the German Federal Ministry of Education and Research and the Land Brandenburg for supporting this project by providing resources on the high performance computer system at the Potsdam Institute for Cli- mate Impact Research. We thank three anonymous referees for their valuable comments and suggestions which helped to improve the manuscript.
Subjects: F700 Ocean Sciences
F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: John Coen
Date Deposited: 05 Aug 2022 13:09
Last Modified: 05 Aug 2022 13:15

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