Search for: All records

Abstract. The ice shelves of the West Antarctic Ice Sheet experience basal meltinginduced by underlying warm, salty Circumpolar Deep Water. Basal meltwater,along with runoff from ice sheets, supplies fresh buoyant water to acirculation 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. 

Abstract The stability of the West Antarctic Ice Sheet (WAIS) depends on ocean heat transport toward its base and remains a source of uncertainty in sea level rise prediction. The Antarctic Slope Current (ASC), a major boundary current of the ocean's global circulation, serves as a dynamic gateway for heat transport toward Antarctica. Here, we use observations collected from the Bellingshausen Sea to propose a mechanistic explanation for the initiation of the westward‐flowing ASC. Waters modified throughout the Bellingshausen Sea by ocean‐sea‐ice and ocean‐ice‐shelf interactions are exported to the continental slope in a narrow, topographically steered western boundary current. This focused outflow produces a localized front at the shelf break that supports the emerging ASC. This mechanism emphasizes the importance of buoyancy forcing, integrated over the continental shelf, as opposed to local wind forcing, in the generation mechanism and suggests the potential for remote control of melt rates of WAIS' largest ice shelves. 

Abstract Hydrographic data are analyzed for the broad continental shelf of the Bellingshausen Sea, which is host to a number of rapidly thinning ice shelves. The flow of warm Circumpolar Deep Water (CDW) onto the continental shelf is observed in the two major glacially carved troughs, the Belgica and Latady troughs. Using ship‐based measurements of potential temperature, salinity, and dissolved oxygen, collected across several coast‐to‐coast transects over the Bellingshausen shelf in 2007, the velocity and circulation patterns are inferred based on geostrophic balance and further constrained by the tracer and mass budgets. Meltwater was observed at the surface and at intermediate depth toward the western side of the continental shelf, collocated with inferred outflows. The maximum conversion rate from the dense CDW to lighter water masses by mixing with glacial meltwater is estimated to be 0.37 ± 0.1 Sv in both depth and potential density spaces. This diapycnal overturning is comparable to previous estimates made in the neighboring Amundsen Sea, highlighting the overlooked importance of water mass modification and meltwater production associated with glacial melting in the Bellingshausen Sea. 

Abstract Hydrographic data and tracers from several ship‐based sections show the location and structure of a deep eastern boundary current in the Chile Basin. The current is centered above the Peru‐Chile Trench at 2,500–3,400 m and transports up to 6 Sv of low‐potential vorticity, high‐silicate water south toward Drake Passage. Deep current velocities from direct Lowered Acoustic Doppler Current Profiler measurements are up to about 15 cm/s southward. The hydrographic data, as well as potential vorticity and silicate distributions, show that the current is comprised to a large extent of flow from the west moving along the southern flank of the Sala y Gomez Ridge and Nazca Ridge, and to a lesser extent from a flow along the eastern boundary entering directly from the Panama Basin. At the southern edge of the Chile Trench, the current weakens and partly turns offshore to cross the Chile Ridge through a complex region of passages. Above the southern flank of the Chile Rise the flow joins a broader eastward flow; together, these waters return to the eastern boundary before entering Drake Passage.