Severe melting of ice sheet is found in Antarctica

Severe melting of ice sheet is found in Antarctica

MARIO TAMA/GETTY IMAGES

By Chris Mooney WASHINGTON POST DECEMBER 12, 2016

WASHINGTON — A team of European scientists has found a significant amount of ice sheet melting in East Antarctica during the summer months, in an area that is supposed to be too cold for perceptible ice loss.

The researchers also found that the ice shelf was anything but solid — it had many large pockets of weakness throughout its structure, suggesting a greater potential vulnerability to collapse through a process called ‘‘hydrofracturing.’’

The findings, by researchers from the Netherlands, Belgium, and Germany, were reported in the journal Nature Climate Change.

On the ice sheet covering the Arctic island of Greenland, dramatic melting can be found in the summer. That forms lakes, rivers, and even dangerous ‘‘moulins’’ in the ice, where rivers suddenly run through the thick ice sheet. But East Antarctica is supposed to be different. It is extremely remote and cold and doesn’t generally see such warm temperatures in summer, so its ice tends to remain more pristine.

‘‘Many people refer to East Antarctica as being too cold for significant melt,’’ says Jan Lenaerts, a glaciologist with Utrecht University in the Netherlands. ‘‘There’s marginal melt in summer, but there’s not a lot.’’

That common wisdom has been challenged in the study by Lenaerts and his colleagues. On the very large Roi Baudouin ice shelf in East Antarctica, which floats atop the ocean, they found a very Greenland-like situation in early 2016.

The researchers had traveled to investigate what had been described as a nearly 2-mile-wide ‘‘crater’’ in the shelf, glimpsed by satellite, which some sources believed had been caused by a meteorite.

To the contrary, they found that it was a large icy lake bed, 10 feet deep. In its center were multiple rivers and three moulins that carried water deep down into the floating ice shelf.

The researchers also drilled through the ice and found ‘‘englacial’’ lakes, sandwiched between the surface of the ice shelf and its base, which is in contact with the ocean beneath it. They found 55 lakes on or in the ice shelf, and a number of them were in this buried englacial format.

This means the ice shelf is anything but solid — it had many large pockets of weakness that can lead to collapses. That’s bad news, because when ice shelves fall apart, the glacial ice behind them flows more rapidly to the ocean, raising sea levels.

The researchers postulate that a ‘‘microclimate’’ exists on the ice shelf that made it all possible — and that a similar mechanism is operating on other East Antarctic ice shelves.

‘‘We see similar things going on on neighboring ice shelves, and also for instance on the Amery ice shelf, which is also a notorious, very large ice shelf on East Antarctica,’’ Lenaerts said. ‘‘We see this link between strong winds and blue ice formation, enhanced absorption of solar radiation, and the melt that is enhanced by this process.’’

The researchers are not saying that these processes are caused by human-induced climate change — they note in particular that on the Roi Baudouin shelf, it appears there has been some melting at the surface since the 1980s.

However, Lenaerts said, it is already clear there is much more melt water during warmer summers than in cooler ones. And global warming will gradually produce warmer Antarctic temperatures, which should increase the volume of melt water atop these ice shelves, pushing them still further in the Greenland direction.

This means the shelves could be subject to the risk of hydrofracturing, in which a great deal of meltwater forms atop the shelf and pushes inside of it, eventually leading to a crackup.

That’s what is believed to have happened in the classic case of the shattering of the Larsen B ice shelf in the Antarctic peninsula in 2002. The fear is that it could happen in the East Antarctic too, where there is a massive amount of ice to potentially lose.