For anyone even halfway familiar with climate change, they are probably growing tired of hearing it - but all the same, it should be said: Antarctica's exceptionally important ice shelves are crumbling away at increasingly worrying rates, and we have climate change to blame.
That's at least according to a study recently published in the prestigious journal Science, which details how a team of researchers led by the Scripps Institution of Oceanography have managed to get the best snapshot yet of Antarctica's floating ice shelves. The results show that net shelf melting has increased by as much as 18 percent in some areas over the last two decades.
Past studies have also shown that Antarctica's ice is not in great shape, especially in the wake of warming seas, shifting currents, and record global temperatures. However, the great majority of previous work only focuses on one portion of the ice shelf at a time, or only short snapshots of the ice shelves' behavior.
And that's understandable, as it is very hard to track and assess the state of ice bodies that could cover entire countries. One protruding into the Ross Sea, for instance, is the size of France, according to BBC News.
That's why Scripps researchers Fernando Paolo and Helen Amanda Fricker, alongside oceanographer Laurie Padman of Earth and Space Research, turned to data from not just one long-running satellite, but three successive orbiting missions.
These missions - satellite radar altimetry projects overseen by the European Space Agency (ESA) - lasted from 1994 to 2012, providing the researchers plenty of data that could even be overlapped and compared to ensure an accurate assessment of ice shelf thickness for more than a decade. (Scroll to read on...)
This massive overview of ice change has allowed the researchers to verify some past conclusions - such as the fact that prior to 2003, the ice shelves' overall thickness changed very little. However, thanks to the overarching nature of their data, they were also able to conclude that after 2003 the East Antarctic Ice shelf stopped gaining volume. With the east shelf no longer counteracting losses from other portions of the White Continent, the shelf saw rapid losses.
"Eighteen percent over the course of 18 years is really a substantial change," Paolo said in a statement. "Overall, we show not only the total ice shelf volume is decreasing, but we see an acceleration in the last decade."
Thomas Wagner, Program Manager for Cryospheric Sciences at NASA Headquarters, added that these results not only show the power of overlapping satellite mission data, but also have big implications for future climate change projections.
"With data spanning decades, we can understand some of the most important changes and their implications for sea-level rise," he said.
Fricker went on to explain that because ice expands, melting ice floating on the surface of the ocean traditionally cannot impact sea level rise. In most cases it's the ice that's on land, as seen in various parts of the Arctic, that experts worry about.
However, there is still an important indirect impact that must be considered.
"The ice shelves buttress the flow from grounded ice into the ocean, and that flow impacts sea-level rise," Fricker said, "so that's a key concern from our new study."
In other words, with thinning ice shelf coverage, melting continental ice will flow into the ocean sooner, contributing to an ever-accelerating rise in sea levels. And with the current rates of thinning in mind, Fricker and his colleagues estimated that the ice shelves in West Antarctica - potentially holding back a great deal of meltwater in the unstable region - could lose half their current volume within the next 200 years.
With a better idea of how much ice is melting from the shelves, the researchers now hope to better determine what influences this phenomenon - information that could be invaluable for predicting future losses.
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