Environmental Science and Engineering Seminar

Global lakes and wetlands are significant natural sources of atmospheric methane. Arctic landscapes, which are currently warming 3-4x faster than the global average, have the highest density of lakes in the world. In the mid and high Arctic, lakes are largely thought to be well-mixed in the summer due to a short ice-free period and relatively cold summer temperatures that limit thermal stratification from developing. High-latitude northern lakes are thus largely considered to be the least vulnerable (of global lakes) to developing summer stratification over the coming century, although there are strongly conflicting projections on this point. Given that most observations over the last ~50 years demonstrate that mid and high Arctic lakes are well-mixed in the summer, and that there is sparse real-time monitoring of the stratification status of Arctic lakes overall, the contribution of Arctic lakes to ongoing and future methane emissions is highly uncertain and possibly vastly undercounted. This talk will discuss how biomarkers in Holocene paleorecords from mid and high Arctic Greenland lakes inform our understanding of lake summer mixing regimes during past sustained warming and whether summer stratification appears to be the exception or the rule when the Arctic warms.