Climate and atmospheric drivers of historical terrestrial carbon uptake in the province of British Columbia, Canada

Y. Peng,B. J. Hawkins,J. C. Fyfe,A. T. Werner,R. A. Hember,W. A. Kurz,V. K. Arora

doi:10.5194/bg-11-635-2014

Abstract

Abstract. The impacts of climate change and increasing atmospheric CO2 concentration on the terrestrial uptake of carbon dioxide since 1860 in the Canadian province of British Columbia are estimated using the process-based Canadian Terrestrial Ecosystem Model (CTEM). Model simulations show that these two factors yield an enhanced carbon uptake of around 44 gC m−2 yr−1 (or equivalently 63 gC m−2 yr−1 over the province's forested area), during the 1980s and 1990s, and continuing into the 2000s. About three-quarters of the simulated sink enhancement in our study compared to pre-industrial conditions is attributed to changing climate, and the rest is attributed to increase in CO2 concentration. The model response to changing climate and increasing CO2 is corroborated by comparing simulated stem wood growth rates with ground-based measurements from inventory plots in coastal British Columbia. The simulated sink is not an estimate of the net carbon balance because the effects of harvesting, insect disturbances and land-use change are not considered.

Highlights

Atmospheric carbon dioxide (CO2) concentration is increasing due to emissions from anthropogenic use of fossil fuels and changes in land use
This evidence includes (1) flux towers measuring the land–atmosphere exchange of CO2 typically over an area of a few square kilometres (e.g. Krishnan et al, 2008; Yuan et al, 2009), (2) inversion-based studies using atmospheric transport models in conjunction with observations of atmospheric CO2 to infer the location of sinks and sources of carbon on the continental scale (e.g. Deng et al, 2007; Deng and Chen, 2011; Gourdji et al, 2012), (3) inventory-based studies (Pan et al, 2011), and (4) modelling approaches where terrestrial ecosystem models are driven by observed atmospheric CO2 concentration and climate (e.g. Huntzinger et al, 2012)
For application over British Columbia (BC) at a spatial resolution of 40 km we found that, while Canadian Terrestrial Ecosystem Model (CTEM)’s single needleleaf evergreen plant functional types (PFTs) yields reasonable leaf area index (LAI) and gross primary productivity (GPP) in the coastal region compared to observation-based estimates, it yields unrealistically low LAI and vegetation biomass in the interior of the province

Summary

Introduction

Atmospheric carbon dioxide (CO2) concentration is increasing due to emissions from anthropogenic use of fossil fuels and changes in land use. Several lines of evidence indicate that carbon uptake is occurring in northern mid- to high-latitude regions (Ciais et al, 2010). This evidence includes (1) flux towers measuring the land–atmosphere exchange of CO2 typically over an area of a few square kilometres Krishnan et al, 2008; Yuan et al, 2009), (2) inversion-based studies using atmospheric transport models in conjunction with observations of atmospheric CO2 to infer the location of sinks and sources of carbon on the continental scale In inversion-based studies the inferred carbon sink is a function of atmospheric transport of CO2 and prior estimates of CO2 fluxes and boundary conditions

Results

Discussion

Conclusion