Credit: British Antarctic Survey
Hot news from the Far South. Hundreds of glaciers flowing off the Antarctic Peninsula have sped up, dumping ever more ice into the ocean and contributing significantly to the rise in worldwide sea level.
The new study by the British Antarctic Survey used satellite images to track the flow rate of 300 glaciers no one had studied before and found the startling results. Antarctic melt may be contributing as much to sea level rise as Alaska.
The new study add details to an alarming picture of an icy habitat in fast transition: the Antarctic Peninsula was already showing dramatic increases in summer melt and ice shelf retreat.
Blame climate warming, the scientists reported in a news release about the study.
“The Antarctic Peninsula has experienced some of the fastest warming on Earth, nearly 3 °C over the last half-century,” said lead author Dr. Hamish Pritchard, in the release. “Eighty-seven percent of its glaciers have been retreating during this period and now we see these glaciers are also speeding up.”
Most evidence that global warming has been accelerating comes from the Far North, with the steady retreat of the Arctic ice cap among the most dramatic. Earlier this spring, researchers at the National Snow and Ice Data Center reported that Arctic ice shrink may be 30 years ahead of worst-case predictions.
But evidence of climate chance in the Far South has been much less conclusive. Total Antarctic ice extent has not changed much, and scientists still debate the stability of the continent’s extensive ice shelves. Still, the peninsula has been warming fast.
Credit: British Antarctic Survey
Now comes some new data. The BAS — one of the world’s top polar research groups — used radar images taken by two European satellites to track the flow rates of about 300 glaciers off the peninsula. The speed that glacial ice flowed downslope into the ocean increased 12 percent in just 10 years, from 1993 to 2003.
The results were written up by Prichard and D. G. Vaughan, with Widespread acceleration of tidewater glaciers on the Antarctic Peninsula published this week in the Journal of Geophysical Research.
The scientists explain further:
These observations — that echo recent findings from coastal Greenland — indicate that the cause is melting of the lower glaciers, which flow directly into the sea. As they thin, the buoyancy of the ice can lift the glaciers off their rock beds, allowing them to slide faster.
As a result, these glaciers are likely increasing sea level about 0.16 mm per year (plus or minus about .06 mm.)
“This is comparable to the contribution from Alaskan glaciers,” Pritchard and Vaughan wrote in the abstract of the paper, “and combined with estimated mass loss from West Antarctica, is probably large enough to outweigh mass gains in East Antarctica and to make the total Antarctic sea level contribution positive.”
The scientists noted that the Intergovernmental Panel on Climate Change did not offer an upper limit on sea-level rise in its February 2007 report largely because no one completely understands how Antarctic ice sheets behave. The new results offer a clearer picture for future estimates, the scientists said.
“It’s important that we use tools such as satellite technology that allow us to monitor changes in remote and inaccessible glaciers on a regional scale,” Pritchard concluded. “Understanding what’s happening now gives us our best chance of predicting what’s likely to happen in the future.”