The active layer of permafrost, which melts and refreezes each year, has increased by more than 1 cm per year in North East Greenland between 1996 and 2008, a study published online this week in Nature Climate Change reports. Although this active layer has deepened, there has not been a detectable decline in carbon stocks in the thawing permafrost as could be expected.
Bo Elberling and co-workers use repeat sediment sampling to assess changes in carbon stocks in Greenland. Measurements of CO2 production from incubated permafrost samples were taken over 12 years to assess the long-term impact of warmer temperatures. They found that there is potential for fast carbon mobilization under oxygen-rich conditions, however when the carbon is near saturation it may remain immobilized for decades.
These results suggest that predictions of carbon release need to consider oxygen availability and the water-ice balance in permafrost.