Warm seawater intrudes into Antarctica’s main ice shelf, raising concerns about sea levels

The vast Antarctic ice sheet stores more than half of the earth’s fresh water. In some places on the continent, the ice extends over the ocean, where it forms large floating shelves. Observations show that many of these ice shelves are thinning as they melt from below, affecting ocean dynamics, global sea levels, and Earth’s climate.

For now, the Filchner-Ronne Ice Shelf, one of Antarctica’s largest ice shelves in the Weddell Sea, remains relatively stable due to near-freezing ocean currents circulating over the continental shelf below. It seems so. However, climate models predict that changes in ocean currents could bring warmer water to the continental shelf in the future.

To get a clearer picture of the future of the Filchner-Ronne Ice Shelf, Professor Steiger analyzed water temperature and current velocity data from 2017 to 2021. The data was captured by bottom moorings along the ocean floor and sensors mounted on underground floats near the ice shelf. The findings are published in the Journal of Geophysical Research: Oceans.

Previous research has shown that during the summer, relatively warm seawater rises from the nearby mid-depths of the ocean to the continental shelf and then along the Filchner Trough on the ocean floor toward the edge of the ice shelf. Ta. However, most of these observations are limited to single site or single year data.

In this study, the researchers found that summer warm water flow occurs not only along the Filchner Trough, but also along a second, smaller trough to the east, and that the relative importance of each pathway varies from year to year. I discovered something different. In warmer-than-average years, warm water flows faster across the continental shelf.

The analysis also highlights two summers in 2017 and 2018 that experienced both an unusually warm inflow and an unusually low amount of floating sea ice. Researchers suggest that less ice changes ocean dynamics, making it easier for warm water to rise and push onto continental shelves.

It is not clear whether the warm flows of 2017 and 2018 actually reached the edge of the Filchner-Ronne Ice Shelf itself. However, researchers observed warm water meeting ice in the summer of 2013, and previous research suggested that this movement of warm water was linked to wind patterns. Continued observations could help reveal the exact cause of this year-to-year difference in warm water flow.

This article is republished courtesy of Eos, sponsored by the American Geophysical Union. Read the original story here.