• Estimating CH4 ebullition from northern lakes using L-band SAR backscatter intensity
    • Melanie Engram
    • April 03, 2015

Northern high latitude thermokarst lakes have been identified as strong sources of atmospheric methane (CH4), a powerful greenhouse gas, with ebullition (bubbling) as the dominant mode of CH4 emission.  Field measurements of CH4 flux (rate of emission) can be extrapolated to regional estimates of lake-source CH4 to the atmosphere.  However, these scaled-up estimates include large uncertainties due to the high spatial and temporal variability of CH4 ebullition.  A remote sensing method which correlates pixel values of lake ice with biogeochemical field measurements of CH4 ebullition could account for natural variability and reduce estimation uncertainties.  In past work, we compared spaceborne synthetic aperture radar (SAR) to field measurements of ice-bound CH4 bubbles from ten thermokarst lakes on the northern Seward Peninsula, Alaska, and found that ebullition bubbles trapped by winter lake ice were strongly correlated with L-band single-polarized (HH) SAR (R2=0.70, P=0.002, n=10) and with the ‘roughness’ component of a Pauli decomposition of L-band quad-polarized SAR (R2=0.77, P=0.001, n=10).  I will present results and associated error from comparison of ground measurements with SAR for three other regions in Alaska, and from our fall 2014 validation campaign on Fairbanks area lakes.  

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  • Water and Environmental Research Center (WERC)
  • 437 Duckering
  • 306 Tanana Loop
  • PO Box 75 5860
  • Fairbanks, AK 99775-5860, USA