Articles | Volume 17, issue 13
Atmos. Chem. Phys., 17, 8619–8633, 2017
Atmos. Chem. Phys., 17, 8619–8633, 2017

Research article 14 Jul 2017

Research article | 14 Jul 2017

Arctic regional methane fluxes by ecotope as derived using eddy covariance from a low-flying aircraft

David S. Sayres1, Ronald Dobosy2,3, Claire Healy4, Edward Dumas2,3, John Kochendorfer2, Jason Munster1, Jordan Wilkerson5, Bruce Baker2, and James G. Anderson1,4,5 David S. Sayres et al.
  • 1Paulson School of Engineering and Applied Sciences, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
  • 2Atmospheric Turbulence and Diffusion Division, NOAA/ARL, Oak Ridge, TN 37830, USA
  • 3Oak Ridge Associated Universities (ORAU), Oak Ridge, TN 37830, USA
  • 4Department of Earth and Planetary Sciences, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA
  • 5Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA

Abstract. The Arctic terrestrial and sub-sea permafrost region contains approximately 30 % of the global carbon stock, and therefore understanding Arctic methane emissions and how they might change with a changing climate is important for quantifying the global methane budget and understanding its growth in the atmosphere. Here we present measurements from a new in situ flux observation system designed for use on a small, low-flying aircraft that was deployed over the North Slope of Alaska during August 2013. The system combines a small methane instrument based on integrated cavity output spectroscopy (ICOS) with an air turbulence probe to calculate methane fluxes based on eddy covariance. We group surface fluxes by land class using a map based on LandSat Thematic Mapper (TM) data with 30 m resolution. We find that wet sedge areas dominate the methane fluxes with a mean flux of 2.1 µg m−2 s−1 during the first part of August. Methane emissions from the Sagavanirktok River have the second highest at almost 1 µg m−2 s−1. During the second half of August, after soil temperatures had cooled by 7 °C, methane emissions fell to between 0 and 0.5 µg m−2 s−1 for all areas measured. We compare the aircraft measurements with an eddy covariance flux tower located in a wet sedge area and show that the two measurements agree quantitatively when the footprints of both overlap. However, fluxes from sedge vary at times by a factor of 2 or more even within a few kilometers of the tower demonstrating the importance of making regional measurements to map out methane emissions spatial heterogeneity. Aircraft measurements of surface flux can play an important role in bridging the gap between ground-based measurements and regional measurements from remote sensing instruments and models.

Short summary
Arctic temperatures have risen faster than the global average, causing the depth of melting of the frozen ground to increase. Previously frozen organic carbon, once exposed to air, water, and microbes, is turned into carbon dioxide and methane, both of which are important greenhouse gases. Due to the large and varied surface area of the Arctic and the difficulty of making measurements there we use a low flying aircraft (<25 m) to measure the amount of methane released from different regions.
Final-revised paper