Thermokarst Lakes as a Source of Atmospheric CH 4 During the Last Deglaciation

Abstract

Polar ice-core records suggest that an arctic or boreal source was responsible for more than 30% of the large increase in global atmospheric methane (CH 4 ) concentration during deglacial climate warming; however, specific sources of that CH 4 are still debated. Here we present an estimate of past CH 4 flux during deglaciation from bubbling from thermokarst (thaw) lakes. Based on high rates of CH 4 bubbling from contemporary arctic thermokarst lakes, high CH 4 production potentials of organic matter from Pleistocene-aged frozen sediments, and estimates of the changing extent of these deposits as thermokarst lakes developed during deglaciation, we find that CH 4 bubbling from newly forming thermokarst lakes comprised 33 to 87% of the high-latitude increase in atmospheric methane concentration and, in turn, contributed to the climate warming at the Pleistocene-Holocene transition.