Satellite view of an ice shelf and sea ice
Part of the Filchner-Ronne Ice Shelf, the largest ice shelf in Antarctica, is seen here from space in February 2017. Credit: Paul Quast, USGS/Flickr, CC BY 2.0
Source: Journal of Geophysical Research: Oceans

The Antarctic Ice Sheet is the largest block of ice in the world. It covers an area 4 times the size of China and holds more than 60% of the world’s fresh water. Where the ice sheet meets the ocean, it forms floating shelves that cool and freshen the salty waters below as they melt. Because of the Antarctic Ice Sheet’s vast size and effects on the ocean, the rates at which its shelves melt play key roles in influencing Earth’s climate.

In a new study, Vaňková and Nicholls used 14 ground-based radars to monitor the rate at which the base of the Filchner-Ronne Ice Shelf (FRIS)—the continent’s largest by ice volume, located in West Antarctica—has been melting both seasonally and annually. The radars collected measurements at least every 2 hours, with the shortest-running device active for several months and the longest-running one active for 6 years. At two of the sites, the team used ocean mooring data to extrapolate further back in time, obtaining up to 15-year-long melt rate time series, by far the longest such measurement in Antarctica.

The researchers found that the highest melt rates follow episodes of low summer sea ice concentrations outside the ice shelf. They also showed that the strength of this melt rate signal is spatially nonuniform across the ice shelf. In comparing the radar time series with satellite data, they found similar average melt rates using both methods. However, the radar data show that melting below broad areas of FRIS varies to a much lower extent than indicated by the existing satellite estimates. In addition, they note, the time series can help scientists determine whether ocean models are accurately predicting melt rate changes and which regions need further ground-based data collection, according to the researchers.

More accurate melt rate measurements offer a better understanding of dynamical interactions between the ocean and the Antarctic Ice Sheet. Understanding ongoing changes and improved capability to reproduce those changes in Earth system models can, in turn, lead to better constraints on sea level rise projections and other climate change impacts, according to the authors. (Journal of Geophysical Research: Oceans,, 2022)

—Rachel Fritts, Science Writer

Citation: Fritts, R. (2022), A close look at melting below Antarctica’s largest ice shelf, Eos, 103, Published on 28 October 2022.
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