LGM Permafrost Thickness and Extent in the Northern Hemisphere derived from the Earth System Model i LOVECLIM

An estimate of permafrost extent and thickness in the northern hemisphere during the Last Glacial Maximum (LGM, ~ 21 ka) has been produced using the VU University Amsterdam Permafrost Snow (VAMPERS) model, forced by iLOVECLIM, an Earth System Model of Intermediate Complexity. We present model results that give both permafrost thickness and extent. In the northern hemisphere, permafrost is estimated to have extended southwards to approximately 50°N in Asia and have achieved 1500 m thickness in Russia. The simulated distribution is compared with a reconstruction of northern hemisphere permafrost extent (Vandenberghe et al., 2014). We contend that the areas which agree with Vandenberghe et al. (2014) are the approximate areas of continuous permafrost during the LGM. In Asia, the model results agree well until approximately 50°N, which is also the approximate 0°C mean annual ground temperature isotherm estimated by iLOVECLIM. South of this limit, therefore, were likely the areas of discontinuous, sporadic and isolated permafrost during the LGM. However, it becomes difficult to model these more sensitive areas of permafrost extent since formation is dependent on local factors that are too fine for our grid's spatial resolution. In Europe, the model results disagree with the reconstruction but this was to be expected since iLOVECLIM is known to carry a warm bias in this region. For permafrost thickness, we compare our estimates with previous research and find that we have reasonably close approximations but there is a wide range of uncertainty since the subsurface parameters of lithology and water content are generalised. Copyright © 2015 John Wiley & Sons, Ltd.