Exchange of CO2 and CH4 between a Siberian thaw lake and the atmosphere
Le résumé fourni par la source
Freshwaters are an important component of the \ncontinental greenhouse gas (GHG) balance with emissions \nestimated to correspond to about 80 % of the \nland GHG sink [Bastviken et al., 2011]. Thaw lakes \nin permafrost landscapes and especially in Yedoma \npermafrost are considered to be strong processors of \norganic carbon and essential emitters of CH4 [Walter \net al., 2006]. As the Arctic experiences the recent \nglobal warming at a much faster rate than other regions \nof the world [AMAP, 2015], the importance \nof thaw lakes in the global GHG budget is expected \nto rapidly increase due to progressive permafrost degradation. \nHowever, especially arctic lakes are highly \nunderrepresented in observational studies on lakeatmosphere \nGHG exchange. Only a few short-term \nstudies exist, with a majority missing the ice break-up. \nThis event is assumed to result in a spring emission \npeak that contributes considerably to the annual GHG \nemissions. In consequence, arctic freshwaters are not \nadequately represented in modelling approaches and \nscenarios of climate change. \nUsing a floating eddy covariance (EC) system, we \ninvestigate ecosystem CH4 and CO2 flux dynamics \nbetween the atmosphere and a Yedoma thaw lake \nin the Lena River Delta in northern Siberia. The \ncompiled dataset covers the ice break-up and most of \nthe ice-free period 2014. We chose the EC method \nas it allows direct, automatic and non-intrusive flux \nmeasurements in remote areas. The investigated lake \nis one of > 500 lakes on Kurungnakh Island in the \nLena River Delta. The study site lies within the zone \nof continuous permafrost and belongs to the arctic \ntundra zone. The lake covers an area of approximately \n1.25 km2 with a mean depth of eight meters. \nWe will present first results of this study and discuss \nthe importance of a spring emission peak during ice \nbreak-up in the annual GHG budge
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