Antarctica is leaking from the inside out

The Antarctic Ice Sheet is draining huge quantities of water out to sea.

By Jeremy Deaton Nexus Media 

When climate scientists look at Antarctica, they see a ticking time bomb. If the ice sheet melts, it will raise sea levels by tens of feet, flooding coastal cities around the globe.

For now, the southern continent is relatively stable, but it’s starting to look more like Greenland, where rising temperatures are melting the island from the inside out.

For decades, Greenland primarily melted around the edges. Giant blocks of ice would break free from the coast and vanish into the ocean. Recently, however, Greenland has started melting from the middle. Pools of water are forming atop the ice sheet in the warmer months and then draining out to sea.
Scientists have now discovered the same thing is happening in Antarctica. Two new studies published in the journal Nature catalogue the melting and explain what it could mean for sea-level rise.

In the first study, researchers examined decades of photos from satellites and military aircraft. They documented hundreds of meltwater channels around the perimeter of the continent. They traced some streams deep into Antarctica’s frozen interior and discovered ponds of meltwater more than 4,000 feet above sea level, where no one expected to find liquid H₂O.

In some places, the terrain had contributed to the melting. Blue ice and dark mountains absorb more sunlight than the white snow. These features gathered the extra heat needed to thaw Antarctic ice.

Nature

Exposed rock and blue ice absorb sunlight, accelerating melting.

“Even though people kind of knew there were melt ponds around, they really didn’t know that water could move long distances across the surface,” said Jonathan Kingslake, a glaciologist at Columbia University and lead author of the study. He said that streams “take water away from the surface of the ice sheet and actually export it all the way into the ocean… And we didn’t really realize this happened at all.”

Meltwater channels tend to grow in warmer months and refreeze in the winter. But scientists worry that rising temperatures spur continual melting, accelerating sea-level rise.
Ice shelves along the edge of the continent are holding back massive, terrestrial glaciers. As the shelves break up, they allow glaciers to slip into the ocean. Meltwater may, in some instances, lubricate the underside of the glacier, hastening its passage to the sea. Meltwater can also burrow into the ice shelf, cleaving apart large chunks of ice. This is what’s happening to the Larsen C Ice Shelf, which is expected to break off the continent soon.

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