Literature review of past work

[adele-morrison]

This is a place to record brief notes on past studies that have found a relationship (or not) between ASC strength and cross-slope heat transport. Some initial papers to get us started:

• Ellie's recent paper
• Silvano et al. 2019
• Nakayama et al. 2021
• Not sure if we want to go into the Amundsen papers looking at variations in the undercurrent on the slope and warm water intrusions - this might be a quite different mechanism to where there is a strong westward ASC. Maybe a very brief summary of a couple of these would be nice?

Let's add brief summaries of what these papers found below, and please add more suggestions of papers that have investigated the relationship between the ASC and cross-slope heat transport below.

[ongqingyee]

Si et al. 2023, Heat transport across the Antarctic Slope Front controlled by cross-slope salinity gradients

There is enhanced poleward heat transport in both fresh shelf and dense shelf regimes, resulting from the modification of salt fluxes prescribed on the shelf in an idealised model. "Freshening the shelf leads to baroclinic instabilities of the slope front that drive a shallow overturning, bringing warm waters onto the shelf and exporting fresh surface waters offshore, while salinifying the shelf leads to dense outflows in canyons that drive a warm return flow at mid-depth" A surface-intensified ASC and bottom-intensified ASC arise as a result of the freshening/salinification.

Stewart and Thompson 2015. Eddy-mediated transport of warm Circumpolar Deep Water across the Antarctic Shelf Break

Eddy transport of CDW onto the shelf is "sensitive to all aspects of the ASF surface forcing and geometry [bathymetry], suggesting that shoreward eddy heat transport may be localized to favorable sections of the continental slope". "Easterly wind stress particularly shapes ASF and constrains shoreward CDW flux."

[PaulSpence]

Pena-Molino et al. 2016

Only observations of ASC at longer than seasonal time-scale in East Antarctic. Direct velocity observations from a 17 month current meter moored array deployed across the continental slope between the 1000 and the 4200 m isobaths, in the southeastern Indian Ocean near 1138E.

The observed time-mean flow consists of a surface-intensified jet associated with the Antarctic Slope Front (ASF) and a broader bottom-intensified westward flow that extends out to approximately the 4000 m isobath and is strongest along the upper slope. The time-mean transport of the ASC is 229.2 Sv. Fluctuations in the transport are large, typically exceeding the mean by a factor of 2. They are mainly due to changes in the northward extent of the current over the lower slope. However, seasonal changes in the wind also drive variations in the transport of the ASF and the flow in the upper slope. Both mean and variability are largely barotropic

M1 is on the shelf and M5 is at 4500m depth:

[PaulSpence]

Silvano et al. 2022

Modelling study focussed on the Amundsen Sea undercurrent. Argues that undercurrent behaves differently (more baroclinic) on decadal time-scales - with stronger easterlies increasing the southward heat transport (I don't believe them :).

[PaulSpence]

Klatt et al. 2005

Obs along prime meridion (0 deg). AWI233 is on the slope.

[PaulSpence]

Walker et al. 2007

Amundsen Sea trough obs. "On the basis of new data we calculate that 2.8 terra-Watts of oceanic heat flow onto the continental shelf and toward the glaciers via a submarine glacial trough."

[PaulSpence]

Stewart et al. 2019

Modelling study: These findings imply that the circulation and mean overturning of the ASC are not only determined by near-Antarctic winds, but also depend crucially on sea ice cover, regionally-dependent mesoscale eddy activity over the continental slope, and the amplitude of tidal flows across the continental shelf break.

[PaulSpence]

Beadling et al. 2022

The meltwater forcing dominates the Antarctic shelf response and the models yield strikingly different responses along West Antarctica. The disagreement is attributable to the mean-state representation and meltwater-driven acceleration of the Antarctic Slope Current (ASC). In CM4, the meltwater is efficiently trapped on the shelf by a well resolved, strong, and accelerating ASC which isolates the West Antarctic shelf from warm offshore waters, leading to strong subsurface cooling. In ESM4, a weaker and diffuse ASC allows more meltwater to escape to the open ocean, the West Antarctic shelf does not become isolated, and instead strong subsurface warming occurs.

[PaulSpence]

Yamazaki et al. 2020

Use under ice ARGO data to look at currents in East Antarctica.

Use temp to identify the ASC position: "We also present a proxy for the ASC axis as the 0°C isotherm at 400 dbar based on hydrographies (Bindoff et al., [2000] Whitworth et al., [1998] as the velocity field derived from Argo data cannot resolve the ASC axis. Since the subsurface temperature abruptly varies in a cross-isobath direction near the ASC axis (generally from −0.5°C to 1°C) with a spatial scale on the order of 50 km, the index is not sensitive to the choice of temperature for the scale of our interest."

[PaulSpence]

Hatterman 2018

Analysis of 2859 CTD profiles obtained between 1977 and 2016 by ships and instrumented seals at the Weddell Sea continental slope reveals a seasonal rise of the Antarctic Slope Front thermocline by more than 100 m during the summer.