Observed warming below Fimbulisen Ice Shelf in East Antarctica
22 September 2023

Understanding how climate change influences ocean-driven melting of the Antarctic ice shelves is one of the greatest challenges for projecting future sea level rise. This melting can be caused by higher ocean temperatures and changing currents below the ice.

A new paper in Nature Geoscience describes long-term observations of ocean heat transport to Antarctica and remote forcing mechanisms.

“The East Antarctic ice shelf cavities host cold water masses that limit melting, and only a few short-term observational studies exist on what drives warm water intrusions into these cavities. We analyze nine years of continuous oceanographic records from below Fimbulisen and relate them to oceanic and atmospheric forcing. On monthly time scales, warm inflow events are associated with weakened coastal easterlies reducing downwelling in front of the ice shelf. Since 2016, however, we observe sustained warming, with inflowing Warm Deep-Water temperatures reaching above 0◦C.” explains CRiceS researcher Tore Hattermann of the Norwegian Polar Institute. 

Hattermann is responsible for the Fimbulisen observatory and supervised the work led by PhD-candidate Julius Lauber. The observations come from instruments that were set out during Hattermann’s PhD-work when he was part of a team of 6 who spent 45 days on Fimbulisen Ice Shelf in East Antarctica to install an array of three sub-ice-shelf moorings. These moorings were deployed through hot-water-drilled holes below 400 m thick ice. Since then, the moored instruments have continuously measured temperature and velocity of this almost inaccessible part of the world’s oceans. Hattermann will head back to renew them later this year to continue the time series.

The observations made concur with an increase in satellite-derived basal melt rates of 0.62 m/year, which nearly doubles the basal mass loss at this relatively cold ice shelf cavity. 

“We find that this transition is linked to a reduction in coastal sea ice cover through an increase in atmosphere-ocean momentum transfer and to a strengthening of remote subpolar westerlies. These results imply that East Antarctic ice shelves may become more exposed to warmer waters with a projected increase of circum-Antarctic westerlies, increasing this region's relevance for sea level rise projections.” says Hattermann. 

> Read the whole article here: https://www.nature.com/articles/s41561-023-01273-5