June 5, 2023
A close look at the melting beneath Antarctica's largest ice shelf

A close look at the melting beneath Antarctica’s largest ice shelf

Journal of Geophysical Research: Oceans (2022). DOI: 10.1029/2022JC018879″ width=”800″ height=”530″/>

Map of the Filchner-Ronne Ice Shelf using the polar stereographic projection (PS71), inset shows the location of the study area in Antarctica. The contours mark the thickness of the water column at 100 m intervals, while the color map is saturated at 800 m. Deployment sites include ApRES (black dots), under-ice moorings (blue triangles for time series shown here, green stars for the mooring array and purple square for site 1), and ocean moorings (red squares). Geographic labels are as follows: EIS = Evans Ice Stream, FIS = Foundation Ice Stream, KIR = Korff Ice Rise, HIR = Henry Ice Rise, BI = Berkner Island. Flow paths are shown schematically. Ronne and Berkner high salinity shelf water (HSSW) inflows are in red and orange, respectively. Blue arrows mark known ice water outflows. Our results show that the interannual variability of the Ronne HSSW volume propagates to the center of the Ronne ice sheet (the solid and possibly also the dashed line), but the signal does not reach the back of the trough behind the KIR and HIR (the dashed line ). The dashed purple line indicates a plausible two-year, faster-flowing alternative to R05. Credit: Journal of Geophysical Research: Oceans (2022). DOI: 10.1029/2022JC018879

The Antarctic ice sheet is the largest block of ice in the world. It covers an area four times the size of China and contains 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 enormous size and effects of the Antarctic ice sheet on the ocean, the rates at which its shelves melt play a key role in influencing Earth’s climate.

In a new study, Vaňková and Nicholls used 14 ground-based radars to track the rate at which the base of the Filchner-Ronne Ice Shelf (FRIS)—the continent’s largest ice by volume, located in West Antarctica—has been melting as seasonally . and annually.

The radars collected readings at least every two hours, with the shortest-running device active for several months and the longest operating for six years. At two of the sites, the team used ocean mooring data to extrapolate further back in time, obtaining melt rate time series of up to 15 years, 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 uneven across the ice shelf. Comparing the radar time series with the satellite data, they found similar average melt rates using both methods.

However, radar data show that melting beneath large areas of FRIS varies to a much lesser degree than indicated by 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 areas need further data collection on the ground, according to the researchers.

More accurate melt rate measurements offer a better understanding of the dynamic interactions between the ocean and the Antarctic ice sheet. Understanding ongoing changes and an improved ability to reproduce those changes in Earth system models may, in turn, lead to better constraints on predictions of sea-level rise and other impacts of climate change, according to the authors. .

The research was published in Journal of Geophysical Research: Oceans.

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More information:
Irena Vaňková et al, Ocean Variability Beneath the Filchner-Ronne Ice Shelf inferred from base melt rate time series, Journal of Geophysical Research: Oceans (2022). DOI: 10.1029/2022JC018879

Provided by the American Geophysical Union

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

Reference: A close look at melting under Antarctica’s largest ice shelf (2022, October 28) Retrieved October 28, 2022 from https://phys.org/news/2022-10-antarctica-largest-ice-shelf.html

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