New research conducted by scientists from the University of East Anglia reveals that the Ross Ice Shelf in Antarctica has been experiencing increased melting over the last four decades due to warming ocean waters. The study, which was the result of an autonomous Seaglider getting stuck underneath the ice shelf, suggests that this trend is likely to continue as climate change drives further ocean warming. The glider, named Marlin, was deployed into the Ross Sea to collect data on ocean processes important for climate, but was pulled into the ice shelf cavity where it remained for four days before re-emerging.
Researchers recorded a 50-meter-thick intrusion of relatively warm water that had entered the cavity from the nearby open water. Water temperatures measured ranged from -1.9°C to a warmer -1.7°C under the ice. Subsequent analysis of the measurements shows that heat transported into the cavity has increased over the last 45 years, most likely due to warming of the Ross Sea as a result of climate change. The findings were published in the journal Science Advances, with lead author Dr. Peter Sheehan explaining that the slight temperature increase of four thousandths of a degree a year could lead to additional ice loss of 20 to 80 cm per year.
The issue of warm water melting the underside of ice shelves is a significant concern as this process contributes to Antarctic ice-mass loss. The melting of floating ice itself does not substantially raise sea levels, but it destabilizes ice shelves which can lead to the accelerated delivery of land ice to the ocean and increased global sea-level rise. One of the factors that can drive warm surface water under the Ross Ice Shelf is wind, particularly southward surface ocean flows caused by Ekman currents.
Dr. Sheehan and co-author Prof. Karen Heywood used long-term measurements of wind and ocean temperature, along with a model to fill in gaps in the record, to calculate the strength of southward Ekman heat transport over the last 45 years. They found that the heat transported into the cavity by Ekman currents has increased over time. This trend is likely linked to warming of the Ross Sea, as warmer waters today will transport more heat energy into the cavity than in the past. Prof. Heywood emphasized the importance of incorporating the influence of surface-water intrusions and Ekman dynamics into climate models to better understand the impacts of continued ocean warming on Antarctic land-based ice.
This study is the first to examine this process using a long-term dataset, whereas previous understanding of surface-water intrusions came mainly from observations in open water and within ice shelf cavities. The research was funded by organizations such as the UK Natural Environment Research Council, the US National Science Foundation, and the European Research Council Horizon 2020 program. The findings highlight the urgent need to incorporate these processes into climate models to better predict the impacts of continued warming on Antarctic ice shelves and sea-level rise.
