The Antarctic Coastal Current in the Bellingshausen Sea

Abstract

Abstract. The ice shelves of the West Antarctic Ice Sheet experience basal melting induced by underlying warm, salty Circumpolar Deep Water. Basal meltwater, along with runoff from ice sheets, supplies fresh buoyant water to a circulation feature near the coast, the Antarctic Coastal Current (AACC). The formation, structure, and coherence of the AACC has been well documented along the West Antarctic Peninsula (WAP). Observations from instrumented seals collected in the Bellingshausen Sea offer extensive hydrographic coverage throughout the year, providing evidence of the continuation of the westward flowing AACC from the WAP towards the Amundsen Sea. The observations reported here demonstrate that the coastal boundary current enters the eastern Bellingshausen Sea from the WAP and flows westward along the face of multiple ice shelves, including the westernmost Abbot Ice Shelf. The presence of the AACC in the western Bellingshausen Sea has implications for the export of water properties into the eastern Amundsen Sea, which we suggest may occur through multiple pathways, either along the coast or along the continental shelf break. The temperature, salinity, and density structure of the current indicates an increase in baroclinic transport as the AACC flows from the east to the west, and as it entrains meltwater from the ice shelves in the Bellingshausen Sea. The AACC acts as a mechanism to transport meltwater out of the Bellingshausen Sea and into the Amundsen and Ross seas, with the potential to impact, respectively, basal melt rates and bottom water formation in these regions.

Variability and Dynamics of Along‐Shore Exchange on the West Antarctic Peninsula (WAP) Continental Shelf

“…The first order current structure in Bransfield Strait is a cyclonic gyre with a southwestward branch, a cold and strongly barotropic form of the AACC (or CC in previous work), which carries water from the Weddell Sea as it flows around the tip of the Peninsula and enters the strait (Heywood et al., 2004; Thompson et al., 2009; Sangrà et al., 2011; Zhou et al., 2002). Note that prior studies suggest there is no strong continuity between the AACC in the Weddell Sea and Bransfield Strait and the coastal current with the same name formed farther downstream in the Bellingshausen Sea (Moffat et al., 2008; Schubert et al., 2021). The northeastern path of the gyre is the Bransfield Current, which flows northeastward along the South Shetland Islands (Niiler et al., 1991; Sangrà et al., 2011; Savidge & Amft, 2009; Zhou et al., 2002, 2006).…”

“…Mesoscale eddies are critical for the delivery of CDW to the cWAP and this water mass is preferentially carried onshore in the large submarine troughs typical of the bathymetry of this region (Couto et al., 2017; Martinson & McKee, 2012; Moffat et al., 2009). Near the coast, a main feature of the circulation is the Antarctic Coastal Current (AACC, in prior work, the Antarctic Peninsula Coastal Current–APCC), a narrow, coastally‐trapped current flowing along the WAP (Moffat et al., 2008; Savidge & Amft, 2009; Schubert et al., 2021). The mCDW‐dominated deep layer and the upper layers, with WW and AASW, form the southern boundary of the SBF.…”

Antarctic Peninsula warming triggers enhanced basal melt rates throughout West Antarctica

“…The Antarctic Coastal Current (AACC), a geostrophically balanced oceanic boundary current found along the coast and ice shelf fronts ( 24 ), connects the different marginal seas of West Antarctica ( 25 ). The AACC originates at the WAP as the result of strong glacial melt concentrating low salinity near the coast ( 24 , 26 ), although surface wind forcing can also generate sea-surface height (SSH) gradients that support the current ( 27 ).…”

Growth and early life stage of Antarctic silverfish (Pleuragramma antarctica) in the Amundsen Sea of the Southern Ocean: evidence for a potential new spawning/nursery ground

“…We agree that Antarctic silverfish larvae may be carried by AACC flows from the Bellingshausen Sea to the Amundsen Sea and Ross Sea. Schubert et al (2021) used surface drifters to provide further support for evidence that the AACC flows in the Bellingshausen Sea are connected to the Amundsen Sea. The results showed that a drifter released in the central Bellingshausen Sea on March 15, 2007, reached the Amundsen Sea on December 24 (Schubert et al 2021).…”

“…Schubert et al (2021) used surface drifters to provide further support for evidence that the AACC flows in the Bellingshausen Sea are connected to the Amundsen Sea. The results showed that a drifter released in the central Bellingshausen Sea on March 15, 2007, reached the Amundsen Sea on December 24 (Schubert et al 2021). Based on these results, it is impossible for AACC flows to carry larvae from the Bellingshausen Sea to the Amundsen Sea in such a short time (25-54 days).…”