Warming oceans seen as main cause of glacier meltdown on the Antarctic Peninsula

Disintegration of ice shelves in East Antarctica could result in a spiraling increase in sea levels. PHOTO BY BOB BERWYN.
Warming ocean water is creeping up the continental shelf around the Antarctic Peninsula and melting glaciers in some parts of the region. @bberwyn photo.

Staff Report

British researchers say regional patterns of melting of glaciers on the Antarctic Peninsula are linked with warming oceans in the region. The Antarctic Peninsula is one of the biggest contributors to sea level rise, so the new finding will help pinpoint how fast and how high seas will rise in the decades ahead.

The southernmost glaciers flowing to the coast on the western side of the Peninsula are retreating rapidly, but those in the north show little change, the scientists said in a new study published last week in the journal Science. Since accurate measurements started in the 1940s, 94 percent of the 674 glaciers in the region have retreated.

The findings change the way scientists think about the effects of global warming in Antarctica. Most previous evidence suggested that atmospheric warming was the main cause of the meltdown, but the warming ocean may be a bigger factor, said Swansea University researcher Dr. Alison Cook in a press release accompanying the study.

“The numerous glaciers on the Antarctic Peninsula give a key insight as to how environmental factors control ice behavior on a wide scale,” Cook said. “Almost all glaciers on the western side end in the sea, and we’ve been able to monitor changes in their ice fronts using images as far back as the 1940s. Glaciers here are extremely diverse and yet the changes in their frontal positions showed a strong regional pattern.

“We were keen to understand what was causing the differences, in particular why the glaciers in the north-west showed less retreat than those further South and why there was acceleration in retreat since the 1990s,” he continued. “The ocean temperature records have revealed the crucial link.”

After analyzing temperature data from around the peninsula from the last few decades, as well as photography and satellite data of the 674 glaciers, the researchers found that the north-south gradient of increasing glacier retreat was found to show a strong pattern with ocean temperatures, whereby water is cold in the north-west, and becomes progressively warmer at depths below 100 meters farther south. Importantly, the warm water at mid-depths in the southerly region has been warming since as long ago as the 1990s, at the same time as the widespread acceleration in glacier retreat.

Warm waters intruding onto the continental shelf and spreading toward the coast carry heat to the glaciers, causing them to break up and melt, said study co-author Mike Meredith, of the British Antarctic Survey.

“These new findings demonstrate for the first time that the ocean plays a major role in controlling the stability of glaciers on the western Antarctic Peninsula. These waters have become warmer and moved to shallower depths in recent decades, causing glacier retreat to accelerate.”

The researchers emphasized the speed with which the glaciers are changing.

We have known the region is a climate warming hotspot for a while, but we couldn’t explain what was causing the pattern of glacier change,” said Professor Tavi Murray, who leads the Glaciology Research Group at Swansea University.

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