Consistent Timing of Arctic Permafrost Loss Across the CESM1 Large Ensemble

Abstract

The Arctic is especially vulnerable to climate change and is warming faster than the global average. Changes in this region pose a heightened threat due to the immense amount of carbon frozen as organic material in the soil. When permafrost thaws, organic material decays and releases as greenhouse gases into the atmosphere, contributing to further warming. A better understanding of the processes that influence permafrost degradation is needed to inform climate adaptation and mitigation planning. This study assesses changes to Arctic permafrost across 35 ensemble member simulations from the Community Earth System Model 1 Large Ensemble Project, under the Representative Concentration Pathway 8.5 21st century scenario. Most Arctic near‐surface permafrost is lost by 2100, but timing varies across regions and with soil depth. Internal climate variability, represented by differences between ensemble members, has a constrained influence on degradation timing due to relative consistency of summer temperature increases and insulation by winter snow cover.

Evaluating permafrost definitions for global permafrost area estimates in CMIP6 climate models

“…Commonly, individual studies use a single method to define the presence of permafrost. However, some studies have provided insights into the uncertainty between methods with an ad hoc comparison of permafrost presence based on only a few definitions of permafrost extent [16][17][18]. Typically, they find substantial variations in the derived global permafrost area, indicating a considerable impact of permafrost definitions on estimates of the spatial extent of permafrost.…”