Journal
AGRICULTURAL AND FOREST METEOROLOGY
Volume 244, Issue -, Pages 42-56Publisher
ELSEVIER
DOI: 10.1016/j.agrformet.2017.05.006
Keywords
North America drought; North America carbon cycle; Climate change; Ecosystem modeling; Carbon source and sink ecossys
Categories
Funding
- NSERC Discovery Frontiers (DF) grant through Arctic Development and Adaptation to Permafrost in Transition (ADAPT)
- NASA ROSES Grant [NNX10AG01A, NNH10AN681]
- NASA [134164, NNX10AG01A] Funding Source: Federal RePORTER
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The North American (NA) terrestrial biosphere has been a long-term carbon sink but impacts of climate extremes such as drought on ecosystem carbon exchange remain largely uncertain. Here, changes in biospheric carbon fluxes with recent climate change and impacts of the major droughts of the past 30 years on continental carbon cycle across NA were studied using a comprehensive mathematical process model, ecosys. In test of these model responses at continental scale, the spatial anomalies in modeled leaf area indices, fully prognostic in the model, from long-term (1980-2010) means during major drought events in 1988 and 2002 agreed well with those in AVHRR NDVI (R-2 = 0.84 in 1988, 0.71 in 2002). Net ecosystem productivity (NEP) modeled across NA declined by 92% (0.50 Pg C yr(-1)) and 90% (0.49 Pg C yr(-1)) from the long-term mean (+0.54 Pg C yr(-1)), in 1988 and 2002 respectively. These significant drops in NEP offset 28% of the carbon gains modeled over the last three decades. Although the long-term average modeled terrestrial carbon sink was estimated to offset similar to 30% of the fossil fuel emissions of NA, only 0.03% and 3.2% were offset in 1988 and 2002 leaving almost all fossil fuel emissions to the atmosphere. These major drought events controlled much of the continental-scale interannual variability and mainly occurred in parts of the Great Plains, southwest US and northern Mexico. Although warming in northern ecosystems caused increasing carbon sinks to be modeled as a result of greater gross primary productivity with longer growing seasons, elsewhere in the continent frequent drought events of the past 30 years reduced carbon uptake and hence net carbon sinks of the NA.
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