Hydrography, circulation, and response to atmospheric forcing in the vicinity of the central Getz Ice Shelf, Amundsen Sea, Antarctica

Abstract

Abstract. Ice shelves in the Amundsen Sea are thinning rapidly as ocean currents bring warm water into the cavities beneath the floating ice. Although the reported melt rates for the Getz Ice Shelf are comparatively low for the region, its size makes it one of the largest freshwater sources around Antarctica, with potential consequences for, bottom water formation downstream, for example. Here, we use a 2-year-long novel mooring record (2016–2018) and 16-year-long regional model simulations to describe, for the first time, the hydrography and circulation in the vicinity of the ice front between Siple and Carney Island. We find that, throughout the mooring record, temperatures in the trough remain below 0.15 ∘C, more than 1 ∘C lower than in the neighboring Siple and Dotson Trough, and we observe a mean current (0.03 m s−1) directed toward the ice shelf front. The variability in the heat transport toward the ice shelf appears to be governed by nonlocal ocean surface stress over the Amundsen Sea Polynya region, and northward to the continental shelf break, where strengthened westward ocean surface stress leads to increased southward flow at the mooring site. The model simulations suggest that the heat content in the trough during the observed period was lower than normal, possibly owing to anomalously low summertime sea ice concentration and weak winds.

Modeling Ocean Circulation and Ice Shelf Melt in the Bellingshausen Sea

“…The mCDW intrusions toward the Venable and Abbot ice shelves show seasonal variability with higher velocities in summer, only in the coastal area (see Figures 12e and 12f). However, the seasonal variability of mCDW intrusions (current velocities) tends to be weak near the coast (K. Assmann et al., 2019; Dotto et al., 2019; Dundas et al., 2022; Ha et al., 2014; T.‐W. Kim et al., 2017; B. Webber et al., 2017).…”

Unsteady Circulation in a Glacial Fjord: A Multiyear Modeling Study of Milne Fiord

“…In Antarctic ice shelf cavities, the direct intrusion of the coastal shelf current is also the mechanism by which under ice water is renewed (e.g., Bradley et al, 2022;De Rydt et al, 2014;Gwyther et al, 2014;Steiger et al, 2022). The coastal shelf current's density variations, responsible for the barotropic and front modes are not unique to Milne Fiord either; similar or greater variability is found on, or near the continental shelf of East Greenland (Rykova et al, 2015), Northeast Greenland et al, 2017, Svalbard (Nilsen et al, 2008) and West Antarctica (Dundas et al, 2022;Webber et al, 2017). To summarize, the fact Milne Fiord has a comparable geometry, stratification, buoyancy forcing (Appendix B) and offshore forcing to other glacial fjords and ice shelf cavities indicates analogous unsteadiness (on time scales longer than 1 month) may be found in other systems.…”