Multi-Year Estimates of Regional Alaskan Net CO2 Exchange: Constraining a Remote-Sensing Based Model with Aircraft Observations

Jakob Lindaas1, Roisin Commane1, Kristina A Luus2, Rachel Ying-Wen Chang3, Charles E Miller4, Steven J Dinardo5, John Henderson6, Marikate Ellis Mountain7, Anna Karion8,9, Colm Sweeney8,10, John B Miller8,11, John C Lin12, Bruce C Daube13, Jasna V. Pittman14 and Steven C Wofsy15, (1)Harvard University, Cambridge, MA, United States, (2)Max Planck Institute for Biogeochemistry, Jena, Germany, (3)Dalhousie University, Halifax, NS, Canada, (4)California Institute of Technology, Jet Propulsion Laboratory, Pasadena, United States, (5)Jet Propulsion Lab, Pasadena, CA, United States, (6)Atmospheric and Environmental Research, Lexington, MA, United States, (7)Verisk Atmospheric and Environmental Research, Lexington, United States, (8)University of Colorado at Boulder, CIRES, Boulder, CO, United States, (9)National Institute of Standards and Technology, Gaithersburg, United States, (10)NOAA, Global Monitoring Laboratory, Boulder, United States, (11)NOAA Boulder, ESRL, Boulder, United States, (12)University of Utah, Department of Atmospheric Sciences, Salt Lake City, UT, United States, (13)Harvard University, John A. Paulson School of Engineering and Applied Sciences, Cambridge, United States, (14)Harvard University, Harvard John A. Paulson School of Engineering and Applied Sciences, Cambridge, United States, (15)Harvard University, Cambridge, United States
Abstract:
The Alaskan region has historically been a sink of atmospheric CO2, but permafrost currently stores large amounts of carbon that are vulnerable to release to the atmosphere as northern high-latitudes continue to warm faster than the global average. We use aircraft CO2 data with a remote-sensing based model driven by MODIS satellite products and validated by CO2 flux tower data to calculate average daily CO2 fluxes for the region of Alaska during the growing seasons of 2012 and 2013. Atmospheric trace gases were measured during CARVE (Carbon in Arctic Reservoirs Vulnerability Experiment) aboard the NASA Sherpa C-23 aircraft. For profiles along the flight track, we couple the Weather Research and Forecasting (WRF) model with the Stochastic Time-Inverted Lagrangian Transport (STILT) model, and convolve these footprints of surface influence with our remote-sensing based model, the Polar Vegetation Photosynthesis Respiration Model (PolarVPRM). We are able to calculate average regional fluxes for each month by minimizing the difference between the data and model column integrals. Our results provide a snapshot of the current state of regional Alaskan growing season net ecosystem exchange (NEE). We are able to begin characterizing the interannual variation in Alaskan NEE and to inform future refinements in process-based modeling that will produce better estimates of past, present, and future pan-Arctic NEE. Understanding if/when/how the Alaskan region transitions from a sink to a source of CO2 is crucial to predicting the trajectory of future climate change.
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