Necessary Conditions for Warm Inflow Toward the Filchner Ice Shelf, Weddell Sea. Issue 22 (17th November 2020)

• Record Type: Journal Article
• Authors: Daae, K.; Hattermann, T.; Darelius, E.; Mueller, R. D.; Naughten, K. A.; Timmermann, R.; Hellmer, H. H.
• Is Part Of: Geophysical research letters. Volume 47:Issue 22(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-17
• Subjects: ice shelf basal melting -- regime shift -- Antarctic slope front; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL089237
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Understanding changes in Antarctic ice shelf basal melting is a major challenge for predicting future sea level. Currently, warm Circumpolar Deep Water surrounding Antarctica has limited access to the Weddell Sea continental shelf; consequently, melt rates at Filchner‐Ronne Ice Shelf are low. However, large‐scale model projections suggest that changes to the Antarctic Slope Front and the coastal circulation may enhance warm inflows within this century. We use a regional high‐resolution ice shelf cavity and ocean circulation model to explore forcing changes that may trigger this regime shift. Our results suggest two necessary conditions for supporting a sustained warm inflow into the Filchner Ice Shelf cavity: (i) an extreme relaxation of the Antarctic Slope Front density gradient and (ii) substantial freshening of the dense shelf water. We also find that the on‐shelf transport over the western Weddell Sea shelf is sensitive to the Filchner Trough overflow characteristics. Plain Language Summary: The Weddell Sea continental shelf is presently filled with water masses that are too cold to melt the Filchner‐Ronne Ice Shelf from below. If warmer offshore water masses gain access to the Weddell Sea continental shelf and flow into the ice shelf cavity, the ocean‐driven melting would increase rapidly and cause ice shelf thinning. Increased ice shelf melting would supply the continental shelf with freshwater that influence sea ice production and generation of dense water masses and cause an increased discharge of grounded ice, which would contribute to global sea level rise. Two main factors currently prevent warm water from accessing the Weddell Sea continental shelf. First, the warm water is located deeper than the continental shelf and does not have direct access. Second, the Weddell Sea continental shelf is filled with dense water masses that block an inflow of warmer and lighter water. We use a regional ocean model to investigate what would happen if the warm offshore water is lifted higher up or if the dense water masses become fresher and lighter. We find that the Weddell Sea system is robust, and we need to make extreme changes to both factors to allow warm water access to the continental shelf. Key Points: Thermocline heaving and freshening of the high‐density shelf water are both needed to cause a cold‐to‐warm regime shift in the Weddell Sea The presence of dense shelf water in Filchner Trough limits inflow of warm water toward the Filchner Ice Shelf front Reduced Filchner Trough overflow may cause increased on‐shelf transport, and thus warming, in the western Weddell Sea