Modelling the impact of ocean warming on melting and water masses of ice shelves in the Eastern Weddell Sea |
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Authors: | Malte Thoma Klaus Grosfeld Keith Makinson Manfred A Lange |
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Institution: | 1. Bayerische Akademie der Wissenschaften, Kommission für Glaziologie, 80539, München, Germany 2. Alfred Wegener Institute for Polar and Marine Research (AWI), Bussestrasse 24, 27570, Bremerhaven, Germany 3. British Antarctic Survey (BAS), High Cross, Madingley Road, Cambridge, CB3 0ET, UK 4. Energy, Environment and Water Research Center (EEWRC), The Cyprus Institute, P.O. Box 27456, CY-1645, Nicosia, Cyprus
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Abstract: | The Eastern Weddell Ice Shelves (EWIS) are believed to modify the water masses of the coastal current and thus preconditions
the water mass formation in the southern and western Weddell Sea. We apply various ocean warming scenarios to investigate
the impact on the temperature–salinity distribution and the sub-ice shelf melting in the Eastern Weddell Sea. In our numerical
experiments, the warming is imposed homogeneously along the open inflow boundaries of the model domain, leading to a warming
of the warm deep water (WDW) further downstream. Our modelling results indicate a weak quadratic dependence of the melt rate
at the ice shelf base on the imposed amount of warming, which is consistent with earlier studies. The total melt rate has
a strong dependence on the applied ocean warming depth. If the warming is restricted to the upper ocean (above 1,000 m),
the water column (aside from the mixed surface layer) in the vicinity of the ice shelves stabilises. Hence, reduced vertical
mixing will reduce the potential of Antarctic Bottom Water formation further downstream with consequences on the global thermohaline
circulation. If the warming extends to the abyss, the WDW core moves significantly closer to the continental shelf break.
This sharpens the Antarctic Slope Front and leads to a reduced density stratification. In contrast to the narrow shelf bathymetry
in the EWIS region, a wider continental shelf (like in the southern Weddell Sea) partly protects ice shelves from remote ocean
warming. Hence, the freshwater production rate of, e.g., the Filchner–Ronne Ice Shelf increases much less compared with the
EWIS for identical warming scenarios. Our study therefore indicates that the ice-ocean interaction has a significant impact
on the temperature-salinity distribution and the water column stability in the vicinity of ice shelves located along a narrow
continental shelf. The effects of ocean warming and the impact of increased freshwater fluxes on the circulation are of the
same order of magnitude and superimposed. Therefore, a consideration of this interaction in large-scale climate studies is
essential. |
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