6 December 2005

Arctic Soil Carbon Vastly Underestimated

by Kate Melville

It seems that current efforts to understand the effects of carbon on climate warming could be a waste of time as estimates of Arctic soil carbon appear to be hugely underestimated. New University of Washington research shows that the estimate of how much soil carbon is available in the high Arctic to be released into the atmosphere could be out of whack by a factor of one hundred or more.

The three year study of soils in northwest Greenland found that a key previous study greatly underestimated the organic carbon stored in the soil because the researchers only looked at the top 10 inches of soil. The earlier study, reported in 1992, estimated nearly 1 billion metric tons of organic carbon in the soil of the polar semi-desert, a 623,000-square-mile treeless Arctic region that is 20 - 80 percent covered by grasses, shrubs and other small plants. That research also estimated about 17 million metric tons of carbon was sequestered in the soil of the adjacent polar desert, a 525,000-square-mile area where only 10 percent or less of the landscape is plant covered.

But the new study made significantly different findings. University of Washington (UW) researcher Jennifer Horwath said the team dug substantially deeper - in some instances more than 3 feet down - and found significantly more carbon. Horwath's astonishing conclusion was that the polar semi-desert contains more than 8.7 billion metric tons of carbon, and the polar desert contains more than 2.1 billion metric tons. "In the polar semi-desert, I found nearly nine times more carbon than was previously reported," she said. "In the polar desert, I'm finding 125 times more carbon." The new findings were presented today at the American Geophysical Union's fall meeting. The work is part of a broader study of carbon content of the water, plants and soil of the high Arctic region being conducted by the University of Alaska.

Horwath says the findings are significant because the Arctic is showing greater effects from global climate change than anywhere else. "We already know the Arctic climate is warming, and as it warms the depth of the permafrost is lowered. As that happens, more carbon becomes active and can be converted to carbon dioxide, one of the most abundant greenhouse gases in the atmosphere," she explained.

She added that the carbon estimate discrepancy may invalidate many computer models used to predict future climate trends. "The effects of climate change are really hard to predict, and it's that much harder if you don't have an accurate picture of what is actually happening now," said concluded.

Source: University of Washington