Researchers find Antarctic ice shelves have experienced only minor changes in surface melt, but expect the rate to increase
The authors of the new CU Boulder-led assessment expect surface melt to increase in the coming decades.
Antarctic ice shelves have experienced only minor changes in surface melt rates over the past four decades, unlike the rapid increase in surface melt experienced by Greenland’s glaciers during the same time period, according to new research.
The news is not cause for celebration just yet though; the researchers expect Antarctic ice shelf surface melt rates to increase substantially in the coming decades due to rising global air temperatures.
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Surface melt rates
Ice shelves are the parts of glaciers that extend into the ocean and float on top of seawater.
In a new study, glaciologists combined satellite microwave data with computer modelling to quantify how much surface melt occurred on all Antarctic ice shelves from 1980 to 2021.
The study was led by Alison Banwell, a glaciologist at the Cooperative Institute for Research in Environmental Sciences (CIRES), a partnership between the University of Colorado Boulder and the US National Oceanic and Atmospheric Administration.
The results show Antarctic ice shelves overall have seen only minor changes in surface melt rates over the past 40 years, and the modelling results even show a small but significant decrease in melt rates during the study period.
However, some ice shelves on the Antarctic Peninsula, which juts out of the continent toward South America, did experience exceptionally high surface melt in recent years, especially during the austral summer of 2019-2020.
The findings appear to be good news for the Antarctic region, but the researchers caution that they do expect Antarctic ice shelves to see higher surface melt in the coming decades.
And surface melting is not the only threat ice shelves face; scientists tracking the Thwaites Ice Shelf in West Antarctica have found warm ocean water is eating away at the fragile ice shelf from below.
Banwell said: “As air temperatures increase over the coming decades, we’re expecting a real increase in these surface melt rates up until the end of the century.
“So although we haven’t seen much change in melt rates yet, we will see that to come.
“It just hasn’t really kicked off yet.”
Ice shelves help stabilise upstream glaciers from otherwise flowing more rapidly into the ocean, but ice shelves are susceptible to surface melting and melting from warm ocean water below.
The polar regions are particularly vulnerable to warming temperatures, and researchers have seen substantial melt on Greenland’s ice sheet over the past few decades, but Antarctica’s response to climate change has varied.
Some areas of the continent, like the Antarctic Peninsula, have warmed dramatically, both other regions have not.
After studying the surface melt of one Antarctic ice shelf from 1980 to 2021, Banwell decided to look at all the continent’s ice shelves to see how (and if) they have changed over the past 40 years.
Her new study is the first to combine satellite microwave data with a computer model to quantify surface melt over all the continent’s ice shelves.
The satellite data showed how many days meltwater was present on each ice shelf, while the computer model estimated the volume of meltwater produced on each day there was meltwater present.
The results show that collectively, Antarctic ice shelves experienced hardly any change in surface melt over the past four decades and there was even a small but significant decrease in surface melt, according to the model the researchers used.
However, the researchers do expect to see an increase in surface melt in the coming decades.
Surface melt makes ice shelves less stable by thinning them and changing how they respond to stress.
Banwell said: “As temperatures increase… melt rates will rise, ice shelves are going to become much less stable as decades go on by the end of the century.”
The new study is published in Geophysical Research Letters.
Image: Paradise Bay, Antarctica. Credit: amanderson2 (CC BY 2.0) https://creativecommons.org/licenses/by/2.0 via Wikimedia Commons.