Modeling Ocean Circulation and Ice Shelf Melt in the Bellingshausen Sea

The ice shelves in the Bellingshausen Sea are melting and thinning rapidly due to modified Circumpolar Deep Water (mCDW) intrusions carrying heat toward ice-shelf cavities. Observations are, however, sparse in time and space, and extensive model-data comparisons have never been possible. Here, using a circulation model of the region and ship-based observations, we show that the simulated water mass distributions in several troughs traversing mCDW inflows are in good agreement with observations, implying that our model has the skills to simulate hydrographic structures as well as on-shelf ocean circulations. It takes 7.9 and 11.7 months for mCDW to travel to the George VI Ice Shelf cavities through the Belgica and Marguerite troughs, respectively. Ice-shelf melting is mainly caused by mCDW intrusions along the Belgica and Marguerite troughs, with the heat transport through the former being similar to 2.8 times larger than that through the latter. The mCDW intrusions toward the George VI Ice Shelf show little seasonal variability, while those toward the Venable Ice Shelf show seasonal variability, with higher velocities in summer likely caused by coastal trapped waves. We also conduct particle experiments tracking glacial meltwater. After 2 years of model integration, similar to 33% of the released particles are located in the Amundsen Sea, supporting a linkage between Bellingshausen Sea ice-shelf meltwater and Amundsen Sea upper ocean hydrography. The Bellingshausen Sea Ice Shelves have been affected by high ice-shelf melt and ice-loss rates in Antarctica. The reason for the ice loss is the presence of warm modified Circumpolar Deep Water (mCDW) over the continental shelf, which intrudes into ice-shelf cavities. Recently, studies combining observations and models have significantly advanced our understanding of Ice-Ocean interactions around Antarctica. For example, in the Amundsen Sea, the region neighboring the Bellingshausen Sea and contributing the most to Antarctic glacial ice loss, such an approach has revealed the drivers and pathways of ocean heat intrusions as well as the impact of glacial meltwater on the Antarctic coastal circulation. We follow this approach and evaluate our ocean model by comparing it with ship-based and satellite-based observations. Using this model simulation, we show that the simulated mCDW intrudes from the continental shelf break toward ice-shelf cavities mainly through two deep cross-shelf troughs. The glacial meltwater is transported by the westward Antarctic Coastal Current (AACC) flowing into the Amundsen Sea. The mCDW inflow and AACC in the coastal area show seasonal variabilities with higher velocities in the summer, which are likely caused by coastal trapped waves. The simulated hydrographic structures over the Bellingshausen Sea continental shelf region are in good agreement with observations The warm water intrusions toward the Venable Ice Shelf show peaks of higher velocities in summer, likely caused by coastal trapped waves Glacial meltwater from about 33% of the area underneath the BS ice shelves flows into the Amundsen Sea within 2 years