- Research Reveals ‘Eddy Mechanism’ behind How Warm Seawater Melts the Antarctic Ice Shelves, Published in the International Journal Communications Earth & Environment -

 In the midst of the unprecedented Antarctic glacial meltdown triggered by climate change in recent years, the Ministry of Oceans and Fisheries (Minister CHO, Seung-Hwan) and the Korea Polar Research Institute (President KANG, Sung-Ho) have successfully found the key to predicting how quickly the Antarctic glaciers will melt. In a world-first, the process of how an eddy, generated in the austral summer coast, channeled the warm surface waters of the ocean into the cavity below the ice shelves was discovered. While it was a well-known fact that the warmer ocean waters from global warming melt the glaciers of Antarctica, the mechanism behind how its warm surface waters flowed into the ice shelf cavities that lay hundreds of meters below was not fully understood.

 Ice shelves are huge masses of ice 200~900 meters thick that stretch out from the terrestrial glaciers of the Antarctic continent and float on top of the ocean, which prevent glaciers from falling into the water. Glacial ice from the land raises the sea levels proportionally to scale, making ice shelf calving a major element of sea level changes.

 Meanwhile, it is said that sea levels on Earth will rise by about 58m when all the Antarctic ice melts. This is a height that can sink not only the coastal cities of Incheon, Busan, and New York but also the inland cities of Seoul and London. Therefore, analyzing the causes of Antarctic ice shelf melting and predicting their future is extremely critical in our responses to climate change.

 The results of the study are a set of accomplishments delivered by a joint team of international researchers led by Dr. LEE, Won-Sang of the Korea Polar Research Institute, initiated in 2019 as a R&D project of the Ministry of Oceans and Fisheries to identify the causes of the ice shelf melting in Antarctica. In addition to the Polar Research Institute, Kyungpook University of Korea, the University of California and Columbia University of the US, and University of Auckland of New Zealand took part in the research. The team approached the Nansen Ice Shelf in 2019 on the icebreaker RV Araon and observed underwater activity by using an unmanned underwater glider as there were limits to what could be understand with the naked eye.

 The autonomous underwater glider collected information, including the water temperature, salinity, and oxygen saturation, with its sensors from an expansive area while the Araon remained nearby the ice shelves. The research team analyzed the directions and speed of the seawater based on the data collected by the glider, and discovered that an eddy, 10km in diameter and rotating clockwise, transported the heat of the warm surface water to the calving front of a cold-water cavity ice shelf.

Nansen Ice Shelf: an ice shelf nearby the Jang Bogo science station in Antarctica, where an 214㎢ calving (circle in the left image) fell and flowed towards the ocean (circle in the right image, image observed by the Arirang satellite)

 While it was assumed that the warm surface water would have been transported to the bottom of the ice shelves, this was the first finding in the world to have observed and revealed the process. The eddy in front of the Nansen Ice Shelf is a natural phenomenon that temporarily occurs in the summer of the Southern hemisphere, which was confirmed to have been created by the integrated actions of multiple factors, including the katabatic winds, the coastal currents flowing along the coasts, and the melted water emitted from the bottom of the ice shelf. This eddy upwells the cold middle layer water while deepening the warm surface water, thereby accelerating the basal melt rate of the ice shelf.

 The research is meaningful in that it has allowed us to make more accurate predictions of the melt rates of ice shelves in the future by understanding the existence of eddies. Scientists can now predict that glaciers found in regions affected by eddies will melt faster than previously expected. As the research team expects similar eddy-driven activity in the Thwaites glacier of West Antarctica, the most vulnerable region of the continent to climate change as the lower part of the glacier is located below sea level, they plan to start field exploration from the end of 2023.

 The research findings were published in the June edition of the international journal Communications Earth & Environment. The edition showcased three articles in the same volume, including the findings of the Polar Research Institute as well as research findings from Japan and Belgium, together with an article emphasizing the urgent need to study sea level changes that react sensitively to climate change.

 Deputy Minister Song Myeong-dal, the Head of the Marine Policy Office at the Ministry of Oceans and Fisheries praised the “dedication and hard work of the Korean research team in observing the changes first-hand, despite the extreme Antarctic environment, and revealing the secret of how seawater melts the Antarctic ice for the first time in the world.” He also pointed out that “proactively responding to climate change, by expanding scope of such research to the whole of Antarctica, will reveal the causes and the rates of the melting of the ice shelves, and provide support for related research, such as on predicting the rise in global sea levels.”