Articles | Volume 16, issue 8
Atmos. Chem. Phys., 16, 5383–5398, 2016
Atmos. Chem. Phys., 16, 5383–5398, 2016

Research article 29 Apr 2016

Research article | 29 Apr 2016

Investigating Alaskan methane and carbon dioxide fluxes using measurements from the CARVE tower

Anna Karion1,2,a, Colm Sweeney1,2, John B. Miller1,2, Arlyn E. Andrews2, Roisin Commane3, Steven Dinardo4, John M. Henderson5, Jacob Lindaas3,b, John C. Lin6, Kristina A. Luus7,c, Tim Newberger1,2, Pieter Tans2, Steven C. Wofsy3, Sonja Wolter1,2, and Charles E. Miller4 Anna Karion et al.
  • 1Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
  • 2NOAA Earth System Research Laboratory, Global Monitoring Division, Boulder, CO, USA
  • 3School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
  • 4Jet Propulsion Laboratory, Pasadena, CA, USA
  • 5Atmospheric and Environmental Research, Lexington, MA, USA
  • 6Atmospheric Sciences, University of Utah, Salt Lake City, UT, USA
  • 7Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany
  • anow at: National Institute of Standards and Technology, Gaithersburg, MD, USA
  • bnow at: Colorado State University, Fort Collins, CO, USA
  • cnow at: Dublin Institute of Technology, Dublin, Ireland

Abstract. Northern high-latitude carbon sources and sinks, including those resulting from degrading permafrost, are thought to be sensitive to the rapidly warming climate. Because the near-surface atmosphere integrates surface fluxes over large ( ∼  500–1000 km) scales, atmospheric monitoring of carbon dioxide (CO2) and methane (CH4) mole fractions in the daytime mixed layer is a promising method for detecting change in the carbon cycle throughout boreal Alaska. Here we use CO2 and CH4 measurements from a NOAA tower 17 km north of Fairbanks, AK, established as part of NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), to investigate regional fluxes of CO2 and CH4 for 2012–2014. CARVE was designed to use aircraft and surface observations to better understand and quantify the sensitivity of Alaskan carbon fluxes to climate variability. We use high-resolution meteorological fields from the Polar Weather Research and Forecasting (WRF) model coupled with the Stochastic Time-Inverted Lagrangian Transport model (hereafter, WRF-STILT), along with the Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM), to investigate fluxes of CO2 in boreal Alaska using the tower observations, which are sensitive to large areas of central Alaska. We show that simulated PolarVPRM–WRF-STILT CO2 mole fractions show remarkably good agreement with tower observations, suggesting that the WRF-STILT model represents the meteorology of the region quite well, and that the PolarVPRM flux magnitudes and spatial distribution are generally consistent with CO2 mole fractions observed at the CARVE tower. One exception to this good agreement is that during the fall of all 3 years, PolarVPRM cannot reproduce the observed CO2 respiration. Using the WRF-STILT model, we find that average CH4 fluxes in boreal Alaska are somewhat lower than flux estimates by Chang et al. (2014) over all of Alaska for May–September 2012; we also find that enhancements appear to persist during some wintertime periods, augmenting those observed during the summer and fall. The possibility of significant fall and winter CO2 and CH4 fluxes underscores the need for year-round in situ observations to quantify changes in boreal Alaskan annual carbon balance.

Short summary
Northern high-latitude carbon sources and sinks, including those resulting from degrading permafrost, are thought to be sensitive to the rapidly warming climate. Here we use carbon dioxide and methane measurements from a tower near Fairbanks AK to investigate regional Alaskan fluxes of CO2 and CH4 for 2012–2014.
Final-revised paper