12 November 2010
page last updated: 9 November 2010
Constraining Lake Methane Emissions in the Arctic Using Synthetic Aperture Radar (SAR) Remote Sensing
Freezing of lake surface dramatically shows methane ebullition activity. Frozen methane bubbles appear as white circular objects. Holes in ice (center-left) are caused by higher methane fluxes.
Credit: Melanie Engram
Methane (CH4) is an important greenhouse gas, with a global warming potential 25 times that of CO2 and an atmospheric concentration that has more than doubled since the beginning of the industrial era. Yet the CH4 budget is not clearly understood: there are still large uncertainties in CH4 sources and sinks. Lakes, thermokarst lakes in particular, have recently been identified as a significant source of atmospheric CH4, as carbon is digested by microbes in the thaw bulb beneath the lake and released as CH4 by ebullition (bubbling). Ebullition activity in lakes is spatially patchy and temporally sporadic, creating measurement challenges that have been overcome by surveying layered CH4 bubbles frozen in early lake ice. With the goal to constrain northern lake CH4 flux estimates that were generated by scaling-up these bubble surveys to pan-Arctic estimates, I am comparing spaceborne SAR backscatter brightness to in situ field CH4 measurements from lakes in the Seward Peninsula.