O. Roger Anderson, a biologist at the Earth Institute’s Lamont-Doherty Earth Observatory, explained
why permafrost releases carbon as it thaws.
The ‘active layer’ of soil on top of the permafrost, which may be two to 13 feet deep, thaws each summer and can sustain plant life. This layer releases carbon from the roots of plants that respire out CO2, and from microbes in the soil. Some microbes break down the organic matter into CO2. Others, called archaea, produce methane instead, when conditions are anaerobic—when the soil is saturated with water or no oxygen is available. Methane is 20 to 30 times more potent than carbon dioxide at exacerbating global warming, but it remains in the atmosphere for less time.
As permafrost thaws, the active layer deepens. The microbes become active and plant roots can penetrate further down, resulting in the production of more CO2. The amount of methane generated depends on how saturated the ground is.
Scientists don’t know the relative proportions of carbon dioxide and methane emissions that might result from largescale thawing permafrost, said Anderson, because this has never happened in human history. However, research on the upper layer of the tundra (treeless plains overlying the permafrost) suggests that the average carbon dioxide emissions are about 50 times higher than those of methane.
“And we know that for every 10 degrees Celsius that the soil warms up, the emission of CO2 will double,” said Anderson.
No comments:
Post a Comment