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From Models to Observations: A Case Study for the Filchner-Ronne Ice Shelf

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If you have a question about this talk, please contact Dr. Shenjie Zhou.

Warm water of open ocean origin on the continental shelf of Amundsen and Bellingshausen Seas drives the highest basal melt rates reported for Antarctic ice shelves. This has severe consequences for ice shelf/ice sheet dynamics and the mass balance of the Antarctic Ice Sheet. Ice shelves fringing the broad continental shelf in Weddell and Ross Seas melt at rates orders of magnitude smaller. However, simulations using coupled ice–ocean models forced with the atmospheric output of the HadCM3 SRES -A1B scenario run indicate that the circulation in the southern Weddell Sea might change during the 21st century. As elaborated by additional sensitivity studies, certain environmental settings support the flow of Circumpolar Deep Water derivatives southward underneath the Filchner–Ronne Ice Shelf, warming the cavity and intensifying basal melting. The results also identify a tipping point in the southern Weddell Sea: a positive melt water feedback enhances the shelf circulation and the onshore transport of open ocean heat. Motivated by the model results, the Alfred Wegener Institute in collaboration with the British Antarctic Survey and Norwegian Research Centre participated in two projects (FISP and FISS ) focused on the investigation of the Filchner-Ronne Ice Shelf (FRIS) cavity and the southern Weddell Sea continental shelf. Here, I combine the results from data of four moorings operating beneath FRIS with the most recent survey (PS111-2018) along the FRIS front and across the Filchner Trough, complemented by mooring data recovered during the PS124 -2021 COSMUS cruise. It turns out that wide-ranging atmospheric teleconnections influence sea ice and thus dense water formation in the southern Weddell Sea on interannual time scales. The shelf process (a) controls the cavity circulation, (b) causes mode shifts underneath the northern Filchner Ice Shelf, and© determines the strength of the density barrier at the continental shelf break, thereby affecting the onshore flow of warmer waters. This suggests that keeping an eye on the large-scale atmospheric conditions in the Southern Ocean might be one (easy) way to infer changes in the northern Filchner Trough.

This talk is part of the British Antarctic Survey - Polar Oceans seminar series series.

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