Arctic lands and oceans account for 25 percent of world’s net sink of CO2

October 15th, 2009 - 3:26 pm ICT by ANI  

Washington, October 15 (ANI): In a new study, ecologists estimate that Arctic lands and oceans are responsible for up to 25 percent of the global net sink of atmospheric carbon dioxide (CO2).

In their review paper, David McGuire of the US Geological Survey and the University of Alaska at Fairbanks and his colleagues show that the Arctic has been a carbon sink since the end of the last Ice Age, which over time has accounted for between zero and 25 percent, or up to about 800 million metric tons, of the global carbon sink.

On average, the Arctic accounts for 10-15 percent of the Earth’s carbon sink, according to McGuire.

But the rapid rate of climate change in the Arctic - about twice that of lower latitudes - could eliminate the sink and possibly make the Arctic a source of carbon dioxide.

Carbon generally enters the oceans and land masses of the Arctic from the atmosphere and largely accumulates in permafrost, the frozen layer of soil underneath the land’s surface.

Unlike active soils, permafrost does not decompose its carbon; thus, the carbon becomes trapped in the frozen soil.

“Cold conditions at the surface have also slowed the rate of organic matter decomposition, allowing Arctic carbon accumulation to exceed its release,” said McGuire.

But recent warming trends could change this balance. Warmer temperatures can accelerate the rate of surface decomposition, releasing more carbon into the atmosphere.

“More concerning is that the permafrost has begun to thaw, exposing previously frozen soil to decomposition and erosion,” said McGuire.

These changes could reverse the historical role of the Arctic as a sink for carbon.

“In the short term, warming temperatures could expose more Arctic carbon to decomposition,” said McGuire. “And with permafrost melting, there will be more available carbon to decompose,” he added.

According to McGuire, on the scale of a few decades, the thawing permafrost could also result in a more waterlogged Arctic, a situation that could encourage the activity of methane-producing organisms.

Methane is a very potent greenhouse gas - about 23 times more effective at trapping heat than carbon dioxide on a 100-year time scale.

If the release of Arctic methane accelerates, global warming could increase at much faster rates.

“We don’t understand methane very well, and its releases to the atmosphere are more episodic than the exchanges of carbon dioxide with the atmosphere,” said McGuire.

“It’s important to pay attention to methane dynamics because of methane’s substantial potential to accelerate global warming,” he added. (ANI)

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