The effect of driving climate data on the simulated terrestrial carbon pools and fluxes over North America

Authors

  • C. Garnaud,

    Corresponding author
    1. ESCER Centre, Département des Sciences de la Terre et de l'Atmosphère, Université du Québec à Montréal, Montréal, Canada
    • Correspondence to: C. Garnaud, ESCER Centre, Département des Sciences de la Terre et de l'Atmosphère (PK-2210), Université du Québec à Montréal, C.P. 8888, Succ. Centre-ville, Montréal, Québec H3C 3P8, Canada. E-mail: camille@sca.uqam.ca

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  • L. Sushama,

    1. ESCER Centre, Département des Sciences de la Terre et de l'Atmosphère, Université du Québec à Montréal, Montréal, Canada
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  • V. K. Arora

    1. Canadian Centre for Climate Modelling and Analysis, Environment Canada, University of Victoria, Victoria, Canada
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    • The contribution of this authors to this article was prepared as part of their official duties as Canadian government employees and is reproduced with the permission of the minister for Environment Canada

Abstract

Dynamic vegetation models provide the ability to simulate terrestrial carbon pools and fluxes and a useful tool to study how these are affected by climate variability and climate change. At the continental scale, the spatial distribution of climate, in particular temperature and precipitation, strongly determines surface vegetation characteristics. Model validation exercises typically consist of driving a model with observation-based climate data and then comparing simulated quantities with their observation-based counterparts. However, observation-based datasets themselves may not necessarily be consistent with each other. Here, we compare simulated terrestrial carbon pools and fluxes over North America with observation-based estimates. Simulations are performed using the dynamic vegetation model Canadian Terrestrial Ecosystem Model (CTEM) coupled to the Canadian Land Surface Scheme (CLASS) when driven with two reanalysis-based climate datasets. The driving ECMWF reanalysis data (ERA40) and NCEP/NCAR reanalysis I data (NCEP) show differences when compared to each other, as well as when compared to the observation-based climate research unit (CRU) data. Most simulated carbon pools and fluxes show important differences, particularly over eastern North America, primarily due to differences in precipitation and temperature in the two reanalysis. However, despite very different gross fluxes, the model yields fairly similar estimates of the net atmosphere-land CO2 flux when driven with the two forcing datasets. The ERA40 driven simulation produces terrestrial pools and fluxes that compare better with observation-based estimates. These simulations do not take into account land use change or nitrogen deposition, both of which have been shown to enhance the land carbon sink over North America. The simulated sink of 0.5 Pg C year−1 during the 1980s and 1990s is therefore lower than inversion-based estimates. The analysis of spatial distribution of trends in simulated carbon pools and fluxes shows that the simulated carbon sink is driven primarily by NPP enhancements over eastern United States. © 2013 The Authors and Her Majesty the Queen in Right of Canada. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society.

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