The northern circumpolar permafrost region was much larger in area than at present during times of maximum cooling such as the Last Glacial Maximum (about 21,000 years ago). However, its distribution pattern was also much different. For instance, the area of exposed permafrost land in N-America was smaller because the Laurentide Icesheet occupied almost all of Canada. On the other hand, in Eurasia the permafrost region was much larger extending southwards in dry and ice-free continental areas. In addition, exposed northern sea shelves due to the lower global sea levels also aggraded permafrost.

Much focus has been aimed in the last decade at what will happen to the large stocks of carbon stored in the current permafrost region if the climate continues to warm leading to permafrost degradation. There is concern that a release of greenhouse gases due to decomposition of previously frozen carbon stocks will result in a so-called positive feedback on climate warming further increasing global temperatures. However, in order to understand the global climate system it is also important to understand what has happened to the northern permafrost region after the Last Glacial Maximum (or over glacial/interglacial cycles in general).

Traditionally it was believed that the terrestrial carbon stock during glacial periods was much lower than currently because forest and peatlands were much reduced in size due to a colder and drier climate. However, following the recognition that the current permafrost region holds very large carbon stocks, it has also been postulated that even much larger amounts were stored at times of maximum permafrost extent.

Now that we know how large the northern permafrost region was at the LGM, the aim is to reconstruct how much carbon was stored in the region and what happened to it following the global warming after the Last Ice Age. This research will elucidate the role of permafrost carbon in the global climate system over glacial/interglacial transitions and serve as an analog to what might happened in the near future under conditions of rapid warming.

Extent of the northern circumpolar permafrost region during the Last Glacial Maximum (after Lindgren et al., 2015; Permafrost and Periglacial Processes)
Extent of the northern circumpolar permafrost region during the Last Glacial Maximum (after Lindgren et al., 2015; Permafrost and Periglacial Processes)