The Antarctic Slope and Coastal Currents are key ocean circulation features around the Antarctic margin, driving the transport of heat, salt and nutrients around the continent. They are also coupled to the hydrography of the region, where in certain locations around Antarctica, the weakening of these currents facilitate the cross-slope transport of warm water onto the continental slope, inducing basal melt of ice shelves and increasing glacial and ice sheet flow, resulting in global sea level rise. However, a lack of observations in this remote region limits our understanding of these current systems. This work examined the dynamics of the Antarctic Slope and Coastal Currents, which shed new light on their temporal and spatial variability and has implications on their roles in the climate system.
In Part I of this work we examined an intrinsic variability in warm water intrusions on the Antarctic continental slope through canyons, with narrower canyons resulting in more irregular intrusions in an idealised channel ocean model. Using dynamical systems theory we found that this intrinsic variability arises from the Antarctic Slope Current, driven by feedbacks between eddy generation and surface wind stress input.
In Part 2 of this work we compared eddy and current velocities across a 1/10 degree and 1/20 degree regional ocean-sea ice model, showing that eddy activity is more than doubled in the 1/20 degree model than the 1/10 degree model, with minimal differences in current velocities. Eddy activity and coastal current velocities were found to exhibit a hysteresis loop with sea ice, with sea ice growth leading a dampening of eddy activity and current velocities, a feature more strongly represented in the higher resolution model.
In Part III of this work modelled Antarctic Slope Current changes under a transient meltwater perturbation were investigated, representative of projected meltwater inputs under climate change. The Antarctic Slope Current increases non-linearly over time as more meltwater is added around Antarctica, with an increased acceleration towards the middle of the 21st century. The non-linear acceleration is attributed to a strengthened salinity gradient across the continental slope, driven by poleward shifting warm waters. This work provides new dynamical insight into the variability of these circulation features, but also motivates further investigation into these emergent phenomena to better understand their impact on our changing Antarctic climate.
