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Arctic climate will change faster than Antarctic

Doug O'Harra

Rising temperatures and shifting storm tracks may thaw ice and frozen ground in both the Far North and the Far South during coming decades. But the Arctic -- with its ice cap riding a vast, roiling ocean and its landscape underlain by saturated permafrost -- will change faster than the drier, continental Antarctic, according to a Penn State hydrologist who studies the role played by water in polar ecology.

"The polar regions, particularly the Arctic, are warming faster than the rest of the world," said Michael N. Gooseff, associate professor of civil and environmental engineering, during the 96th annual meeting of the Ecological Society of America in Austin, Tex. "As a consequence, polar ecosystems respond directly to changes in the earth systems at the poles."

Gooseff’s work takes him and his team from one polar region to another, from studies of the McMurdo Dry Valleys of Antarctica to the dynamics of collapsing permafrost on Alaska's North Slope.

"Our focus on the north is in part because it is inhabited, but it is also because the ice there is more vulnerable," said Gooseff, quoted by this story posted online by Penn State. "Temperatures and snow and rain across the tundra shifts annually and seasonally. We know that fall is beginning later than it once did."

The overall climate in the Arctic has been warming in recent decades, with the extent of summer sea ice setting minimum records or near records almost every September. (The latest update found July with the lowest monthly extent seen during the age of satellite monitoring.) Most climate scientists say the steady increase in the concentrations of human-generated greenhouse gases like CO2 play a decisive role in this climate change, by trapping ever-more solar energy in the home planet’s atmosphere.

In the Arctic, retreating summer sea ice allows the darker ocean surface to absorb much more solar energy, which then triggers even more melt, and so on. Likewise, thawing permafrost transforms the Arctic prairie into a boggy, rumpled landscape of holes, channels and chasms -- what scientists call thermokarst. Snowmelt and rain then carve out bigger holes, wider ponds and deeper channels, sending a murky slurry into lakes and streams. Increased sediment and erosion disturb the lives of everything from algae and soil bacteria, to insects, fish and caribou.

It gets worse. All this thawing of ancient permafrost could eventually release mind-boggling stores of carbon that have been trapped inside frozen materials for eons --potentially turbo-charging the greenhouse effect with even more CO2 and methane.

"It is estimated that the permafrost contains twice the amount of carbon that is currently in our atmosphere," said Gooseff, told the society in his remarks.

The changes in soil ecology described by Gooseff are striking. Longer frost-free seasons allow microbes to remain active later in the year, but Arctic plants still follow a seasonal rhythm dictated by daylight and shut down about the same time as they always did. The still-most soil at their roots continues  to sizzle (so to speak) with microscopic life. Unused nutrients end up leaching into rivers and ponds.

"That is exactly what we are seeing," Gooseff told the ecological society. "In September and October, we see a substantial increase in nutrients in the water. Concentrations increase many times for nutrients such as nitrate and ammonium."

But the frozen South will transform much more slowly.

Onshore Antarctica is one of the driest and most desolate places on Earth. But there are several locales with surface water and life -- what Gooseff calls "polar desert oases." In the McMurdo Dry Valleys, ponds and lakes host microbes, plankton and algae.

"While there are no bugs or fish in these waters, there are diverse microbial communities," said Gooseff told the ecological society "Some algae in the dry valleys go dormant for nine months or more and then begin to grown when hit by meltwater."

Because Antarctica is dominated by permanent sheets of ice, increased global temperatures have so far had far less impact than in the Far North. Plus, there are fewer factors that can accelerate the process — almost no exposed water-saturated permafrost, for instance. And summer sea ice retreats only along the edges. The Ice Age still rules the austral pole.

But Antarctica will gradually respond too.

"We expect in the next several decades that we will see the Antarctic start to warm up," Gooseff said.

Contact Doug O'Harra at doug(at)alaskadispatch.com