Coastal freshening enhances eddy-driven heat transfer toward the
Antarctic margins
Abstract
The Antarctic Slope Front (ASF) is a strong gradient in water mass
properties close to the Antarctic margins. Heat transport across the ASF
is important to Earth’s climate, as it influences melting of ice
shelves, the formation of bottom water, and thus the global meridional
overturning circulation. Previous studies based on relatively
low-resolution models have reported contradictory findings regarding the
impact of additional meltwater on onshore heat transport onto the
Antarctic continental shelf: it remains unclear whether meltwater
enhances shoreward heat transport, leading to a positive feedback, or
further isolates the continental shelf from the open ocean. In this
study, heat transport across the ASF is investigated using
high-resolution, process-oriented simulations. It is found that
shoreward heat transport is primarily controlled by the salinity
gradient of the shelf waters: both freshening and salinification of the
shelf waters relative to the offshore waters lead to increased heat flux
onto the continental shelf. For salty shelves, the overturning consists
of a dense water outflow that drives a shoreward heat flux near the
seafloor; for fresh shelves, there is a shallow, eddy-driven overturning
circulation that is associated with an export of fresh surface waters
and a near-surface shoreward heat flux. The eddy-driven overturning
associated with coastal freshening may lead to a positive feedback in a
warming climate: large volumes of meltwater increase shoreward heat
transport, causing further melt of ice shelves.