A research team led by scientists at the University of East Anglia made the remarkable discovery, including how warming ocean waters are causing increased melting of Antarctica’s Ross Ice Shelf over the past 45 years. This discovery, published in Science Advances, was made possible because an autonomous glider, nicknamed Marlin, found itself accidently wedged underneath the ice shelf in December 2022. Initially deployed in the Ross Sea to collect data on ocean conditions, Marlin was then unexpectedly tugged into the cavity below the ice shelf, which it recorded temperature and current data for four days.
Indeed, in 79 dives by Marlin, there is a warmer water layer about 50 meters thick between -1.9°C and -1.7°C. This makes enough to melt the underside of the ice shelf. The warmer water, thus penetrating from the Ross Sea, was located inside the cavity and displaced the colder waters, indicating warming sea conditions are now hitting areas that until then were almost inaccessible to warming.
The scientists believe that heat flux into the ice shelf cavity had increased in the last decades most probably through climate change. Even though the growth rate of warmer water temperature is very small, a little more than four-thousandth of a degree per year, the impact on ice melt is huge, and it could make up for an annual loss of 20 to 80 centimeters of ice over the 45 years of the study. This is the first time such long-term data was used for the analysis of this process in detail as earlier studies were based on very short-term data from ships, tagged seals, or stationary instruments.
The study also takes note of how Ekman currents-wind-driven surface flows that can carry heat to the ice shelf-have become more important. When southward winds force warm surface water under the ice shelf, this heat is immediately available to melt the ice that lies above. Climate change appears to amplify the effect in that warming waters create stronger Ekman currents carrying more heat.
Lead author Dr. Peter Sheehan and his co-author Prof. Karen Heywood warn that future climate models must take into account the trends of this growth in Ekman heat flux and related melting, or otherwise acceleration in ice shelf thinning may quickly lead to land-based ice flow to the ocean and therefore hasten sea-level rise globally.
It investigates how warming seas affect the stability of Antarctic ice under climate change conditions. It is supported by UK Natural Environment Research Council, the US National Science Foundation, and the Horizon 2020 program of European Research Council.