The Antarctic Slope Current in a Changing Climate

Abstract

The Antarctic Slope Current (ASC) is a coherent circulation feature that rings the Antarctic continental shelf and regulates the flow of water toward the Antarctic coastline. The structure and variability of the ASC influences key processes near the Antarctic coastline that have global implications, such as the melting of Antarctic ice shelves and water mass formation that determines the strength of the global overturning circulation. Recent theoretical, modeling, and observational advances have revealed new dynamical properties of the ASC, making it timely to review. Earlier reviews of the ASC focused largely on local classifications of water properties of the ASC's primary front. Here we instead provide a classification of the current's frontal structure based on the dynamical mechanisms that govern both the along‐slope and cross‐slope circulation; these two modes of circulation are strongly coupled, similar to the Antarctic Circumpolar Current. Highly variable motions, such as dense overflows, tides, and eddies are shown to be critical components of cross‐slope and cross‐shelf exchange, but understanding of how the distribution and intensity of these processes will evolve in a changing climate remains poor due to observational and modeling limitations. Results linking the ASC to larger modes of climate variability, such as El Niño, show that the ASC is an integral part of global climate. An improved dynamical understanding of the ASC is still needed to accurately model and predict future Antarctic sea ice extent, the stability of the Antarctic ice sheets, and the Southern Ocean's contribution to the global carbon cycle.

Evolution of the Seasonal Surface Mixed Layer of the Ross Sea, Antarctica, Observed With Autonomous Profiling Floats

“…Moffat et al (2008) discussed the dynamics of buoyancy-driven coastal currents and their dependence on the seasonal modulation of melt rate. Much of this freshwater input at the Ross Sea's eastern boundary past Cape Colbeck flows along the continental slope in the Antarctic Slope Current (Thompson et al, 2018); however, some turns southward into Little America Basin toward the eastern Ross Ice Shelf front (Orsi & Wiederwohl, 2009, their Figure 5b). Realistic numerical model simulations (Dinniman et al, 2015;Kusahara & Hasumi, 2014;Nakayama et al, 2014) also demonstrate this freshwater pathway.…”

Seasonality of Warm Water Intrusions Onto the Continental Shelf Near the Totten Glacier

“…Interaction between currents on the upper continental slope and troughs at the shelf break promotes MCDW intrusions onto the continental shelf (e.g., Dinniman et al, ; Jenkins et al, ; Palóczy et al, ; St‐Laurent et al, ). Easterly winds drive a westward current along most of the Antarctic slope, known as the Antarctic Slope Current (Thompson et al, ). The Antarctic Slope Current transports MCDW, and it is diverted poleward along isobaths when it encounters a trough, resulting in intrusions originating from the east of a trough (Klinck, ).…”

Reduced Sea Ice Production Due to Upwelled Oceanic Heat Flux in Prydz Bay, East Antarctica

“…Although the Antarctic Slope front (ASF) acts as a strong dynamical barrier to the inflow of CDW across the shelf in East Antarctica (Spence et al, ; Thompson et al, ), intrusions of mCDW have been observed in the sea ice growth season (March–August), entering Prydz Bay over Four Ladies Bank (FLB) and occupying the eastern side of the bay following the cyclonic PBG and are directed toward the eastern flank of the AIS (Herraiz‐Borreguero et al, ; Liu et al, ; Williams et al, ). The interaction of the AIS with mCDW heat transport has been clarified by several studies (Herraiz‐Borreguero et al, , ; Wong et al, ), and the AIS net basal melt rate driven by mCDW inflow was estimated at 1.0 ± 0.4 m/year (Herraiz‐Borreguero et al, ), reducing local shelf water density and suppressing its potential contribution to AABW formation (Williams et al, ).…”