Picture (above): Seal at Cape Sherref. Credit: NOAA (Unsplash)
The transport of relatively warm and salty water (known as Circumpolar Deep Water, CDW) from the open ocean to the Antarctic continental shelf has global significance. The amount of warm water that reaches the ice shelves regulates how quickly the ice melts which affects sea levels rise.
At the same time, the amount of salt on the continental shelf regulates how much heat and carbon are stored in the deep ocean through dense water formation.
Yet, the ways in which this circumpolar deep water makes it across the slope and onto the shelf, and the relative importance of the different processes that transport this water, are still unknown.
CLEX researchers have quantified the strength of one of these mechanisms for circumpolar deep water transport – eddy-driven transport – along the continental slope of East Antarctica.
Using a suite of temperature and salinity profiles taken by seals tagged with miniature oceanographic instruments, they found that, in general, eddies transport this deep water across the continental slope to the shelf break – the point where the continental shelf transitions to the continental slope. Closer inspection of this eddy driven transport mechanism revealed specific regions where eddies are much more efficient at carrying circumpolar deep water across the slope (while eddy-driven transport is negligible elsewhere).
The waters at the shelf break are warmer and saltier in these hot spots of eddy-driven transport, and therefore more circumpolar deep water is available to move onto the continental shelf in these locations.
What happens to these regional reservoirs of heat and salt once they move beyond the shelf break will ultimately determine which ice shelves are most vulnerable to ocean-driven melting and where the densest ocean waters are formed.
- Paper: Foppert, A., Rintoul, S. R., & England, M. H. ( 2019). Along‐slope variability of cross‐slope eddy transport in East Antarctica. Geophysical Research Letters, 46, 8224– 8233. https://doi.org/10.1029/2019GL082999