West Antarctica Warming in Triple Time

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The study by Bromwich and colleagues suggests that such exceptional melting events as in January 2005 could become more frequent in the future. Top: Map of Antarctica showing the extent of surface melting in January 2005 observed from space. Bottom: Time series of mean January temperature at Byrd Station from 1957 to 2011 with the warm January 2005 highlighted with a yellow circle. Credit: background map from Google Earth; satellite observations of surface melting courtesy of G. Picard (LGGE)

The West Antarctic Ice Sheet is warming at twice the rate previously

thought, say scientists who have teased the information from more than

50 years of temperature data at Byrd Station, in the center of the ice.

The average temperature at that station has risen 4.3 degrees F (2.4

degrees C) since 1958, which is triple the warming rate of most of the

planet and on par with the very fastest warming parts of the world.

Of

particular concern is that the warming is partially taking place in the

summer months. That's when the already seasonal warmth, plus the new

higher average air temperatures, combine and increase the likelihood of

major melting events that destabilize the ice shelves. Those shelves

hold back a lot of Antarctic glacial ice from reaching the sea,

explained Ohio State University's David Bromwich, the lead author on the

study, which was published in the latest issue of Nature Geoscience.

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“Lots

of melting can do lots of damage to the ice shelves,” Bromwich told

Discovery News. And that can ramp up Antarctica's contribution to sea

level rise worldwide. “We know that these melting events can happen

today and we are likely to see more melting events.”

Researchers

have already documented accelerating of glaciers along the Amundsen Sea

coast, which is dumping more West Antarctic ice into the sea, but

warmer sea temperatures had been seen as the primary cause of that. Air

temperatures have been harder to pin down, due to large gaps in the

records at Byrd Station.

“There are very, very few

observations for that part of the world,” said Davis Schneider an

Antarctic researcher at the National Center for Atmospheric Research,

and not a contributor to the new study. Thinning ice sheets, borehole

temperature readings and ice cores all provide indirect evidence of

warming, he said, but what's been needed is “ground-truthing” with old

fashioned thermometer data.

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“It's those kind of data, that are fragmented, that this study has skillfully reconstructed,” said Schneider.

Two

previous studies using the fragmented Byrd Station air temperature data

had come to conflicting conclusions, which prompted Bromwich and his

colleagues to do the most detailed and careful analysis yet. That

included reconstructing data using climate models and temperature data

from other Antarctic sites.

“We did a very, very careful job of it,” said Bromwich.

The

new work is welcome, said Schneider, because getting a handle on what's

happening in Antarctic air temperatures has not been easy, but it's

essential.

“This is a very first-order question,” said

Schneider. “Hopefully we can move beyond that. There is a lot less

known about Antarctica than the Arctic and we have a lot of catching up

to do.”

Henry Brecher, research associate (now retired) at Byrd Polar Research Center at Ohio State University, took this picture when he was among scientists who “wintered over” at Byrd Station in 1959-1960, close to the time the region’s first temperature data were gathered. Credit: Henry Brecher, courtesy of Ohio State University.

 

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