Carbon cycle uncertainty in the Alaskan Arctic

J. Fisher (1) , M. Sikka (1) , W. Oechel (2) , D. Huntzinger (3) , J. R Melton (4) , C. Koven (5) , A. Ahlström (6) , M. Arain (7) , I. Baker (8) , J. Chen (9) , Philippe Ciais (10, 11) , C. Davidson (12) , M. Dietze (13) , B. El-Masri (12) , D. Hayes (14) , C. Huntingford (15) , A. Jain (12) , P. Levy (16) , M.R. Lomas (17) , B. Poulter (18) , D. Price (19) , A. Sahoo (20) , K. Schaefer (21) , H. Tian (22) , E. Tomelleri (23) , H. Verbeeck (24) , N. Viovy (10, 25) , R. Wania (26) , N. Zeng (27) , C. Miller (1)

1 JPL - Jet Propulsion Laboratory
2 SDSU - San Diego State University
3 Northern Arizona University [Flagstaff]
4 CCCma - Canadian Centre for Climate Modelling and Analysis
5 LBNL - Lawrence Berkeley National Laboratory [Berkeley]
6 Skane University Hospital [Lund]
7 McMaster University [Hamilton, Ontario]
8 CSU - Colorado State University [Fort Collins]
9 Department of Geography and Planning [University of Toronto]
10 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
11 ICOS-ATC - ICOS-ATC
12 UIUC - University of Illinois at Urbana-Champaign [Urbana]
13 BU - Boston University [Boston]
14 ORNL - Oak Ridge National Laboratory [Oak Ridge]
15 CEH - Centre for Ecology and Hydrology [Wallingford]
16 CEH - Centre for Ecology and Hydrology
17 University of Sheffield [Sheffield]
18 MSU - Montana State University
19 NRCan - Natural Resources Canada
20 Princeton University
21 NSIDC - National Snow and Ice Data Center
22 AU - Auburn University
23 MPI-BGC - Max Planck Institute for Biogeochemistry
24 UGENT - Universiteit Gent = Ghent University
25 MOSAIC - Modélisation des Surfaces et Interfaces Continentales
26 UMR ISEM - Institut des Sciences de l'Evolution de Montpellier
27 AOSC - Department of Atmospheric and Oceanic Science [College Park]

Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for the Alaskan Arctic from four recent model intercomparison projects-NACP (North American Carbon Program) site and regional syntheses, TRENDY (Trends in net land atmosphere carbon exchanges), and WETCHIMP (Wetland and Wetland CH 4 Inter-comparison of Models Project)-we provide a baseline of terrestrial carbon cycle uncertainty, defined as the multi-model standard deviation (σ) for each quantity that follows. Mean annual absolute uncertainty was largest for soil carbon (14.0 ± 9.2 kg C m −2), then gross primary production (GPP) (0.22 ± 0.50 kg C m −2 yr −1), ecosystem respiration (Re) (0.23 ± 0.38 kg C m −2 yr −1), net primary production (NPP) (0.14 ± 0.33 kg C m −2 yr −1), autotrophic respiration (Ra) (0.09 ± 0.20 kg C m −2 yr −1), heterotrophic respiration (Rh) (0.14 ± 0.20 kg C m −2 yr −1), net ecosystem exchange (NEE) (−0.01 ± 0.19 kg C m −2 yr −1), and CH 4 flux (2.52 ± 4.02 g CH 4 m −2 yr −1). There were no consistent spatial patterns in the larger Alaskan Arctic and boreal regional carbon stocks and fluxes, with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Finally, AmeriFlux data are used at two sites in the Alaskan Arc-tic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a base-line for the improvement of experimental and modeling activities , as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic and larger boreal region.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

J. Fisher, M. Sikka, W. Oechel, D. Huntzinger, J. R Melton, et al.. Carbon cycle uncertainty in the Alaskan Arctic. Biogeosciences, 2014, 11 (15), pp.4271-4288. ⟨10.5194/bg-11-4271-2014⟩. ⟨hal-02928016⟩