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

• Published in: Atmospheric Chemistry and Physics
• Main Authors: A. Karion, C. Sweeney, J. B. Miller, A. E. Andrews, R. Commane, S. Dinardo, J. M. Henderson, J. Lindaas, J. C. Lin, K. A. Luus, T. Newberger, P. Tans, S. C. Wofsy, S. Wolter, C. E. Miller
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2016
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Arctic; Fairbanks; permafrost; Alaska
• Online Access: https://doi.org/10.5194/acp-16-5383-2016; https://doaj.org/article/4d5bec0aa147429bba4292b849629286

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 (CO 2 ) and methane (CH 4 ) mole fractions in the daytime mixed layer is a promising method for detecting change in the carbon cycle throughout boreal Alaska. Here we use CO 2 and CH 4 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 CO 2 and CH 4 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 CO 2 in boreal Alaska using the tower observations, which are sensitive to large areas of central Alaska. We show that simulated PolarVPRM–WRF-STILT CO 2 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 CO 2 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 CO 2 respiration. Using the WRF-STILT model, we find that average CH 4 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 ...