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Warm Ocean Water Beneath Antarctic Glacier Melts Ice at Unprecedented Rate

First Posted: Sep 13, 2013 10:42 AM EDT
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As our climate changes, our oceans are heating up. The Earth's water helps regulate air temperature, soaking up excess heat. Yet now, we're starting to see some of the impacts of this warming. It turns out that warmer ocean water is melting the Pine Island Glacier's floating ice shelf in Antarctica and may be the culprit for increased melting of other ice shelves.

Pine Island Glacier is a major outlet of the West Antarctic Ice Sheet. Yet in recent years, this ice shelf has rapidly thinned and accelerated. That's why researchers decided to take a closer look to see exactly what was causing this increased melting.

The researchers drilled holes in the ice in order to place a variety of instruments there. In addition, the scientists used radar to map the underside of the ice shelf and the bottom of the ocean. This allowed them to see how the ice shelf was melting.

It turns out that the ice is melting more rapidly from below. Why? The oceans are far warmer than they have been in the past, and water can transfer more heat than air. In addition, the terrain beneath the ice shelf consists of a series of channels. The floating ice in the channel has ample room beneath it for ocean water to flow in. The water melts of the ice beneath and cools, but the channels keep the water from staying long enough to become too cold; this, in turn, accelerates melting.

"The way the ocean water is melting the ice shelf is a deeply non-uniform way," said Sridhar Anandakrishnan, one of the researchers, in a news release. "That's going to be more effective in breaking these ice shelves apart."

An ice shelf breaking apart in the channels is a bit like removing an ice jam from a river. The shelf plugs the channel but once it's gone, the glacier moves more rapidly toward the sea. This forms more ice shelf, but removes large amounts of ice from the glacier. The melting of these floating ice shelves doesn't contribute to sea level rise since they're already in the water, but most of the Antarctic glaciers are on land. This could mean that there might be some major shifts in the future.

"Antarctica is relatively stable, but that won't last forever," said Anandakrishnan. "This is a harbinger of what will happen."

Melting from warmer oceans is an important interaction that should be incorporated into the sea level rise models of global warming. The findings show that this type of melting could have major impacts on future sea level rise.

The findings are published in the journal Science.

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