Published: Fri, April 21, 2017
Science | By Hubert Green

Antarctica's Seasonal Meltwater Networks More Extensive Than Previously Thought

Antarctica's Seasonal Meltwater Networks More Extensive Than Previously Thought

In total, almost 700 seasonal ponds and channels streams were found, with some streams as long as 121 kilometres (75 miles).

Because meltwater streams were thought to be relatively rare in Antarctica before this, they haven't been extensively studied in the past, according to glaciologist Douglas MacAyeal from the University of Chicago, who wasn't involved in the study.

"It shows that we're just starting to understand" the complexities of such systems and that we need "more sophisticated views of the plumbing on our planet", study co-author Robin Bell, a polar researcher at Columbia University's Lamont-Doherty Earth Observatory, said.

Antarctica is already on the verge to lose its ice.

Iceberg shaped by melting, Drake Passage, Palmer Peninsula, Antarctica.

Nothing is clear-cut yet though, and researchers spotted another meltwater stream channel on the Nansen ice shelf that they think might be helping to keep it together, by efficiently removing water from the shelf out to the ocean.

Scientists think Greenland would provide a clue to know how these streams arise and affect sea level rises. Over decades of research on the frozen continent, researchers have documented the occasional stream of meltwater flowing across the icy surface.

No comprehensive view of Antarctica's surface melt features existed.

The study draws on satellite images of the continent dating back to 1973 and aerial photos collected by military planes from as early as 1947. But no one had ever done a systematic survey of Antarctica's meltwater systems.

They found almost 700 drainage systems that formed during the summer melt season, some of which were found farther inland and at higher altitudes than the researchers expected.

On the other hand, in some places, drainage may be crucial to keeping the ice shelves intact. Once this happens, a feedback loop is triggered where the melting ice starts exposing more dark ice as the water flows through the snow. "Meltwater is still a bad thing", she says, but it's "not always going to be a death to ice shelves". The researchers observed that meltwater ponds lurking in Antarctica can be up to several miles wide.

But the main damage to ice shelves comes from ocean water eroding their underbellies. This causes melting of ice.

It's not clear yet from the data whether the meltwater rivers have been growing.

Most vulnerable are the massive, floating ice shelves that ring the Antarctic continent and help prevent inland glaciers from sliding toward the sea, they reported in the journal Nature. As NASA geophycisist Ala Khazendar told NPR in January, "Ice shelves are very important".

Newly recorded drainages usually start near mountains finding their way down through glaciers. A better understanding of how, when and where the meltwater forms could help scientists better model how different ice shelves will respond to rising temperatures, which are expected to increase surface melt.

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