For the past 50 years, the Arctic has been warming three times faster than the average rate of global warming and this warming thaws the permafrost. A new study has revealed that extreme summer rainfall is accelerating the process. As extreme rainfall events become more frequent, the permafrost may thaw even faster than under the influence of rising temperatures alone.
Researchers from Wageningen University carried out an irrigation experiment on the Northeast Siberian tundra to study the effects of extreme summer precipitation on permafrost. They selected 20 monitoring sites and used sprinklers to give half the sites extran water. The experiment simulated the effects of an extremely wet summer. The sites were monitored for several years.
On average, the permafrost thawed 35% faster in the irrigated sites. An important finding was that the effect of an extremely wet summer lasted for several years.
As rainfall is expected to increase and precipitation extremes will become more common in warming Arctic regions, these results are not good for the permafrost. “If we only take warmer temperatures into account, we will underestimate how much permafrost is thawing as a result of climate change, and how much extra CO2 and methane is being released,” explains Ph.D. candidate Rúna Magnusson. “ But it is difficult to realistically represent the effect of such precipitation extremes on permafrost thaw and greenhouse gas emissions in climate models. This could lead us to underestimate future greenhouse gas emissions caused by permafrost thaw, and therefore our emissions targets to stay within the one-and-a-half or two degrees of global warming may turn out to be too optimistic.”
https://phys.org/news/2022-03-permafrost-faster-due-extreme-summer.html