Paper No. 11
Presentation Time: 4:10 PM
POSITIVE FEEDBACKS IN GLOBAL BIOGEOCHEMISTRY: METHANE EMISSIONS FROM FRESHWATER LAKES
Freshwater inland lakes are a significant source of atmospheric methane (CH4), and despite covering less than 1% of the earth’s surface, lakes emit more CH4 than the ocean. With freshwater lakes missing from many atmospheric circulation models, there is a need to quantify their potential climate impact. A positive feedback in the global climate has been observed, with CH4 emissions from lakes increasing as lakes warm. The mechanism involves both an increased production of CH4 in the littoral sediments, and increased diffusive efflux from warm surface water. Methane cycles in lakes were characterized over the course of a summer, and drivers of emissions were determined. Methane production, CH4 storage, and lake surface area to volume ratio were determined to be reliable predictors of CH4 emissions. Additionally, a strong correlation exists between lake productivity and emissions. This suggests that eutrophication may be an amplifier of existing global change mechanisms. Our findings have implications for both existing lakes in temperate and boreal zones, as well as newly forming glacial lakes and wetlands at higher latitudes.