One of the most important sources of the dense, oxygen- and nutrient-rich bottom waters that drive global ocean circulation is Antarctica’s Ross Sea. The cold, salty waters that form in this deep embayment play a crucial role in regulating heat and the availability of oxygen and vital nutrients throughout the world’s oceans.
A significant source of freshwater flowing into the Ross Sea is basal melt from the 34,018-square-kilometer Getz Ice Shelf, which stretches for 650 kilometers along the West Antarctica coast. Because the coastal current steers meltwater from this ice shelf into the Ross Sea, the Getz Ice Shelf’s accelerating basal melt rate has the potential to alter bottom water formation there. Yet despite the region’s importance, dedicated observations near the Getz Ice Shelf’s western front have been extremely limited to date.
Now Assmann et al. present 2 years of continuous velocity and temperature records from several moorings deployed at depths of 600 to 800 meters in a trough that cuts across the continental shelf west of Siple Island. This is one of the areas where warm Circumpolar Deep Water, which has been linked to the rapid thinning and melting of several West Antarctic ice shelves, can reach the Getz Ice Shelf.
The data show there is a continual flow of Circumpolar Deep Water through the Siple Trough. Although this water often undergoes slight cooling or freshening as it approaches the continent, the data indicate there are frequent occasions when undiluted deep water up to 1.5°C—some of the warmest ever observed at an ice shelf front in Antarctica—reaches the western Getz Ice Shelf front.
The authors’ analysis indicates that a combination of wind stress and upwelling at the edge of the continental shelf controls the presence of the warm deep water in this area, although the authors caution that the paucity of data from this region limits their ability to draw robust conclusions. Regardless, this paper is likely to be of great interest to oceanographers and climate scientists who are grappling with the rapid changes occurring in a region with wide-ranging impacts on Earth’s oceans. (Geophysical Research Letters, https://doi.org/10.1029/2018GL081354, 2019)
—Terri Cook, Freelance Writer