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Estimating lake methane ebullition with Synthetic Aperture Radar (SAR)

Melanie Engram, University of Alaska, Fairbanks, melanie.engram@alaska.edu
Katey Marion Walter Anthony, University of Alaska, Fairbanks, kmwalteranthony@alaska.edu (Presenter)
Torsten Sachs, GFX German Research Centre for Geoscience, Potsdam, Germany, torsten.sachs@gfz-potsdam.de
Guido Grosse, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, guido.grosse@awi.de
Franz Josef Meyer, University of Alaska, Fairbanks, fjmeyer@alaska.edu

Lakes cover vast extents of lowland Arctic landscapes and are recognized as a major source of atmospheric methane, a potent greenhouse gas. Yet estimates of Arctic and sub-Arctic lake-source methane emissions are highly uncertain, due in large part to the spatial and temporal irregularity of ebullition (bubbling), but further compounded by the expense and logistical challenge of obtaining enough widespread field measurements to accurately represent a heterogeneous lake-scape. Previous work in synthetic aperture radar (SAR) remote sensing showed backscatter intensity from early winter lake ice correlated with methane ebullition as measured by field surveys in one region in Alaska. Here, we show this relationship holds true for four additional geographic areas in Alaska and create a regionally robust regression model with L-band SAR intensity and methane measurements. We invert this model and, in conjunction with data from long-term bubble traps, estimate methane ebullition from SAR backscatter intensity for over 5,000 lakes on landscape scales. We observed strong lake-size relationships to ebullition and regional variability in lake emissions related to climate and permafrost carbon stocks. Rather than upscaling from a limited number of field observations, our regional lake methane emissions estimates are based on SAR observations for each lake which show increased L-band radar intensity from methane ebullition bubbles disrupting and warping the highly reflective ice/water interface. This new inexpensive approach to remote-sensing lake ebullition offers a unique opportunity to improve knowledge about greenhouse gas fluxes for seasonally ice-covered lakes across the globe.

Associated Project(s): 

Poster Location ID: 5

Session Assigned: Carbon Dynamics

 


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