BOULDER, Colo., Oct. 11 (UPI) -- The conventional scientific wisdom has been that while most of the world has gotten warmer, Antarctica actually has cooled a little, except on its peninsulas and coasts, but new research indicates the polar continent is facing dramatic changes that probably are the result of global warming.
Floating ice shelves are collapsing, vast glaciers are thinning and speeding up in their drift toward the sea, and improvement in the ozone hole probably will result in warming temperatures in the continent's interior.
"We're beginning to push past the normal range of climate variability of the (post-Ice Age) Holocene (period)," said Ted Scambos, a glaciologist at the Snow and Ice Data Center in Denver. "We're seeing the first few steps -- the first few responses -- of a globally warming world. People will point back to these first few years of the 21st century and say that this is when we saw it in the polar regions."
One dramatic impact could be a substantial increase in sea level, well beyond current projections, he said.
"I don't want to mince words," Scambos told United Press International. "It looks to me like we are headed toward a more rapid sea level rise than projected by the IPCC (Intergovernmental Panel on Climate Change) report."
Scambos and his group tracked how the glaciers responded in the Antarctic Peninsula with the breakup of the Larsen B ice shelf. The vast shelf, about the size of Connecticut, collapsed in 2002. Only about one-fifth of it remains.
The collapse the Larsen B, which already was floating, did not increase the sea level, anymore than melting ice cubes raise the level in a gin-and-tonic. Still, the event is significant. Geological evidence suggests the Larsen B had been stable since at least the end of the last ice age -- about 13,000 years ago.
Scambos and his group discovered, however, the Larsen B acted like a stopper in a bottle for the glaciers on the peninsula, and now they have speeded up their flow into the ocean.
"Glaciers that were tributaries to the ice shelf accelerated, not just slowly, but almost immediately by glacier standards," Scambos said.
Within one year of having this ice shelf break away, the rate in the lower parts of the glaciers was five to eight times as fast as it had been. There was a major reorganization of the stresses that control glacier flow, he explained.
"A warming climate in Antarctica is going to initiate a large, rapid change in the mass balance of the ice sheet," Scambos said.
It is known, however, the peninsula where Scambos and colleagues were working has been warming. In fact, it has been warming faster than much of the rest of the Earth. The interior of the continent, however, has not changed much so far. In fact, it has been cooling.
Still, the news from the Antarctic interior is not good.
"We made measurements further south than (the Larsen B)," Robert Thomas, a glaciologist with National Aeronautics and Space Administration contractor EG&G Services, told UPI. "We don't get much summer melting, but we know the glaciers are thinning. At least one, a huge glacier in terms of ice, transported almost 100 cubic kilometers (62 cubic miles) of ice into the ocean. (It) has been accelerating at the same time the ice shelf has been thinning. We think the cork is being pulled out of the bottle. The thinning and acceleration extend more than 100 kilometers (62 miles) inland."
Like Scambos, Thomas's group found acceleration about three to eight times faster.
"This doesn't mean an awful lot to sea level rise," Thomas said. "Only fractions of a millimeter. A big, interesting question is, 'How fast can all of this stuff go?'"
The movement rate of the glacier Thomas and his group studied has accelerated about 25 percent in the past 25 years, just because the ice shelf got thinner.
"What would happen if we took the whole ice shelf away?" he asked. "If that happened to this glacier, it would take several hundred cubic kilometers a year into the ocean. It might contribute more to sea level rise than all the rest of the glaciers in the world -- half a millimeter a year, just from one glacier."
The same thing is happening with other Antarctic glaciers, some the size of Texas.
"We surveyed a lot, and found the same kind of things happening with other glaciers," Thomas said. "The big question is why are these ice shelves getting thinner?"
The surface temperature has not warmed much in the areas Thomas and colleagues are studying, so the most reasonable explanation is that they are being melted by warmer water from below.
"Something is changed in the ocean," Thomas said. When asked what it was he only said: "That's what I'd like to know. More heat must be getting under the glaciers."
There is some evidence deeper water has been warming over the past couple of decades, he added. "That is what one thinks would have to happen, but we don't know it has happened, or why it would have happened."
The most recent IPCC report did not include an assumption the ice shelves act like a cork in a wine bottle. Until fairly recently, in fact, Thomas said, most glaciologists had rejected the idea.
"The models don't include this," he said. "If, indeed, the ocean is changing sufficiently to weaken these ice shelves, we may have an effect we didn't bargain for."
Thus far, Antarctica has shown little sign of the warming climate affecting the rest of the globe, but that may change, and pretty soon, according to Drew Shindell, a research physicist with NASA-Goddard Institute for Space Studies.
While Antarctica has cooled over the past 30 years, Shindell's models indicate it will warm for the next 50, perhaps as much as 2 degrees to 3 degrees Celsius (3.6 to 5.4 degrees Fahrenheit). This is because of a change in circulation.
"If the westerly flow (of air currents) is stronger," Shindell told UPI, "the interior gets more isolated and colder. The peninsula gets warmer. These circulation changes have overridden the general trend (of global warming)."
The depletion of ozone over the continent -- the famous ozone hole -- actually enhanced this westerly shift, and cooling of the continent. Now, however, the ozone is being replenished, and the increased ozone is counteracting the westerly strength of the greenhouse-induced air circulation.
"In the future, the circulation thing goes away," Shindell said. "So you will see warming everywhere" -- both on the coast and in the continental interior.
"It is very uncertain what the threshold would be for a major collapse of the ice sheets," Shindell said. "In the past we haven't worried about it much because it has been getting cooler. If if indeed starts to get warmer, then we do have to start to worry about it more. I don't think we have the understanding to really say ... but there's reason to be concerned. There is no reason to think that the temperature change is too small to have an effect."
Scambos said even current atmospheric carbon dioxide concentrations -- about 375 parts per million -- are higher than any seen in the ice core record, which extends back about half a million years.
"We're seeing the glaciers retreat and respond in ways that they haven't done before in the historical record," Scambos said. "We're beginning down the road to a changed world. We've got no reason to expect that this is going to slow down."
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