Assessment of Model Estimates of Land-Atmosphere CO₂ Exchange Across Northern Eurasia

Michael A Rawlins, University of Massachusetts, Amherst, rawlins@geo.umass.edu (Presenter)
A. David McGuire, USGS, admcguire@alaska.edu
John S Kimball, University of Montana, johnk@ntsg.umt.edu
Pawlok Dass, University of Massachusetts, Amherst, pawlok@geo.umass.edu
David Lawrence, NCAR, dlawren@ucar.edu
Eleanor Burke, Met Office Hadley Centre, eleanor.burke@metoffice.gov.uk
Xiangdong Chen, University of Washington, xiaodc@uw.edu
Christine Delire, CRNM-GAME, cdelire@gmail.com
Charles Koven, Lawrence Berkeley National Laboratory, ckoven@gmail.com
Andrew MacDougall, University of Victoria, amacdo02@uoguelph.ca
Sushi Peng, CEA-CNRS-UVSQ, shushi.peng@lsce.ipsl.fr
Anette Rinke, Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research, annette.rinke@awi.de
Kazuyuki Saito, Japan Agency for Marine-Earth Science and Technology, ksaito@jamstec.go.jp
Wenxin Zhang, Lund University, wenxin.zhang@nateko.lu.se
Ramdane Alkama, CNRS/Meteo-France Toulouse, ramdane.alkama@cnrm.meteo.fr
Theodore J Bohn, Arizona State University, theodore.bohn@asu.edu
Philippe Ciais, CEA Saclay DSM, philippe.ciais@lsce.ipsl.fr
Bertrand Decharme, CNRS/Meteo-France, bertrand.decharme@meteo.fr
Isabelle Gouttevin, LGGE Laboratoire de Glaciologie et Géophysique de l’Environnement, isabelle.gouttevin@gmail.com
Tomohiro Hajima, JAMSTEC Japan Agency for Marine-Earth Science and Technology, hajima@jamstec.go.jp
Duoying Ji, Beijing Normal University, duoyingji@bnu.edu.cn
Gerhard Krinner, LGGE Laboratoire de Glaciologie et Géophysique de l’Environnement, gkrinner@lgge.obs.ujf-grenoble.fr
Dennis P Lettenmaier, University of California - Los Angeles, dlettenm@ucla.edu
Paul Miller, Lund University, paul.miller@nateko.lu.se
John C Moore, Beijing Normal University, john.moore@bnu.edu.cn
Ben Smith, Lund University, ben.smith.lu@gmail.com
Tetsuo Sueyoshi, NIPR National Institute of Polar Research, sueyoshi.tetsuo@nipr.ac.jp

A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land-atmosphere carbon dioxide (CO₂) dynamics through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary productivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of northern Eurasia. The retrospective simulations were conducted over the 1960-2009 record and at 0.5 degree resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO₂ fluxes derived from site-based eddy covariance measurements as well as regional-scale GPP estimates based on satellite remote sensing data. The site-based comparisons show the timing of peak GPP to be well simulated. Modest overestimates in model GPP and ER are also found, which are relatively higher for two boreal forest validation sites than the two tundra sites. Across the suite of model simulations, NEP increases by as little as 0.01 to as much as 0.79 g C m_-2 yr_-2, equivalent to 3% to 340% of the respective model means, over the analysis period. For the multimodel average the increase is 135% of the mean from the first to last ten years of record (1960-1969 vs 2000-2009), with a weakening CO2 sink over the latter decades. Vegetation net primary productivity increased by 8% to 30% from the first to last ten years, contributing to soil carbon storage gains, while model mean residence time for soil organic carbon decreased by 10% (-5% to -16%). This suggests that inputs to the soil carbon pool exceeded losses, resulting in a net gain amid a decrease in residence time. Our analysis points to improvements in model elements controlling vegetation productivity and soil respiration as being needed for reducing uncertainty in land-atmosphere CO₂ exchange. These advances require collection of new field data on vegetation and soil dynamics, the development of benchmarking datasets from measurements and remote sensing observations, and investments in future model development and intercomparison studies. Resulting improvements in parametrizations and processes driving productivity and soil respiration rates will increase confidence in model estimates of net CO₂ exchange, component carbon fluxes, and underlying drivers of change across the northern high latitudes.

Presentation Type:  Poster

Session:  General Contributions   (Tue 4:35 PM)

Associated Project(s): 

• Rawlins, Michael: Synthesis and Integration of Recent Research Characterizing the Carbon Cycle of Northern Eurasia ...details

Poster Location ID: 217