"They are the classic canaries in the coal mine, in that they are responding to changes that are occurring on an enormous scale," Fraser said.
"These are global scale changes; it's just not the [Antarctic] peninsula that's warming."
Doug Martinson is a physical oceanographer at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York.
He noted that the peninsula's especially rapid warming must be tied to factors unique to the region.
(Read "Antarctica's Atmosphere Warming Dramatically, Study Finds" [March 30, 2006].)
"The peninsula is undergoing warming that in the wintertime is almost 5.5 times the global average," Martinson said.
"[There's] got to be some other source of heat that's melting the glaciers and raising the air temperature, and the most obvious source is the ocean."
Water has a much greater capacity to carry heat than air. As the air in equatorial regions gets warmer, this heat makes its way down into the deep ocean.
Deep ocean currents then bring this warmer water toward the South Pole, where it gets "hijacked" by the Antarctic circumpolar current—the "global mix master," as Martinson calls it.
As this current glances off the Antarctic Peninsula, some of its warmer water flows up onto the continental shelf, mixes its way to the surface, and sends heat into the atmosphere.
"The deep-ocean circulation is bringing water to our area of the Antarctic Peninsula that—just a little ways below the water's surface—is four degrees Celsius [seven degrees Fahrenheit] warmer than freezing," Martinson said.
"It's a freight train of hot coals that goes steaming by this frigid area."
In recent decades Martinson has found that the sea ice has started melting much earlier and freezing over much later.
"The summer season with no sea ice is now 85 days longer than it used to be just since the '80s," he said.
"It almost doubles the length of summer down there as far as sea ice goes."
Not All Bad?
But it's not all bad news for the Adélies, said Fraser of the Polar Oceans Research Group.
As the Antarctic Peninsula heats up, southern parts of Antarctica have become more hospitable homes for the species.
Adélie populations in the far southern peninsula have tripled in previous decades, Fraser said.
And ice-intolerant penguin species, such as chinstrap and gentoo penguins, are moving into the warmer Antarctic habitats once occupied by the Adélies.
Since 1974 gentoos have increased in number by 7,500 percent and chinstraps by 2,700 percent.
"We joke that gentoos are going to take over the world," Fraser said.
However the danger remains that all parts of Antarctica could warm past the Adélies' ideal temperature range.
"Pound for pound, an Adélie penguin can deal with just about anything," Fraser said.
"To see them being affected so dramatically by [human-induced] climate change, it's particularly hard to bear."
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