Future increases in Arctic lightning and fire risk for permafrost carbon

Abstract

Lightning is an indicator and a driver of climate change. Here using satellite observations of lightning flash rate and ERA5 reanalysis, we find that the spatial pattern of summer lightning over northern circumpolar regions exhibits a strong positive relationship with the product of convective available potential energy (CAPE) and precipitation. Applying this relationship to CMIP5 climate projections for a high emissions scenario (RCP8.5) shows an increase in CAPE (86 ± 22%) and precipitation (17 ± 2%) in areas underlain by permafrost, causing summer lightning to increase 112 ± 38% by end of century (2081-2100). Future flash rates at northern treeline are comparable to current levels 480 km to the south in boreal forests. We hypothesize that lightning increases may induce a fire-vegetation feedback whereby more burning in Arctic tundra expedites northward migration of boreal trees, with the potential to accelerate the positive feedback associated with permafrost soil carbon release.