The autonomous glider, named Marlin, was deployed in December 2022 to collect data on oceanic processes crucial for understanding climate dynamics. Initially programmed to move north into open water, Marlin was carried south by a current and became lodged beneath the ice shelf for four days. During this time, it completed 79 dives, measuring water conditions up to 200 meters deep and near the base of the ice shelf.
The data revealed a 50-meter-thick layer of relatively warm water infiltrating the cavity from nearby open water, with temperatures between -1.9C and -1.7C. Analysis of historical measurements pointed to a long-term increase in the heat transported into the ice shelf cavity, likely tied to rising temperatures in the Ross Sea.
Dr. Peter Sheehan, the study's lead author, emphasized the implications of even minor temperature increases: "While the temperature increase - four thousandths of a degree a year - might not seem all that much, it could lead to around 20 to 80 cm of additional ice loss per year over the 45 years we look at."
Dr. Sheehan explained that this warm water is capable of melting the ice from below, unlike colder waters that typically remain at freezing points. "What's new here is that we can track the warm water pretty much from the open water of the Ross Sea at the ice front, back into the cavity. We have not seen one of these intrusions happening directly before," he added.
These insights are significant as ice shelves, which float on the ocean and extend from the continent, act as a buffer that slows the flow of land ice into the sea. While the melting of floating ice does not directly raise sea levels, the thinning and potential disintegration of ice shelves could accelerate land ice discharge, contributing to global sea-level rise.
The study also highlighted the role of Ekman currents, surface ocean flows driven by wind, which transport heat beneath the ice shelf. This mechanism allows heat to directly affect the ice without needing to rise from deeper ocean layers. The research team, including Dr. Sheehan and Prof. Karen Heywood, used a blend of historical wind and temperature data along with a model to assess the increase in southward Ekman heat transport over recent decades.
Prof. Heywood noted, "It appears reasonable to expect that the magnitude of the Ekman heat flux, and of the melting that it drives, will increase yet further as climate change drives continued ocean warming. This trend is a concern in itself."
The findings underscore the importance of including these processes in climate models, as understanding their influence is critical for predicting the response of Antarctic ice to a warming climate.
This study represents the first multi-decade analysis of surface-water intrusions impacting an Antarctic ice shelf, improving upon previous studies that relied on more limited observations from ships, tagged animals, and ice-anchored moorings.
Research Report:Ross Ice Shelf frontal zone subjected to increasing melting by ocean-surface waters
Related Links
University of East Anglia
Beyond the Ice Age
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
