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The effect of atmospheric sulfate reductions on diffuse radiation and photosynthesis in the United States during 1995–2013
Author(s) -
KeppelAleks G.,
Washenfelder R. A.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl070052
Subject(s) - environmental science , atmospheric sciences , sink (geography) , carbon sink , photosynthesis , temperate climate , aerosol , primary production , temperate rainforest , sulfate , canopy , climatology , meteorology , chemistry , climate change , geology , ecosystem , oceanography , physics , ecology , geography , biochemistry , cartography , organic chemistry , biology
Aerosol optical depth (AOD) has been shown to influence the global carbon sink by increasing the fraction of diffuse light, which increases photosynthesis over a greater fraction of the vegetated canopy. Between 1995 and 2013, U.S. SO 2 emissions declined by over 70%, coinciding with observed AOD reductions of 3.0 ± 0.6% yr −1 over the eastern U.S. In the Community Earth System Model (CESM), these trends cause diffuse light to decrease regionally by almost 0.6% yr −1 , leading to declines in gross primary production (GPP) of 0.07% yr −1 . Integrated over the analysis period and domain, this represents 0.5 Pg C of omitted GPP. A separate upscaling calculation that used published relationships between GPP and diffuse light agreed with the CESM model results within 20%. The agreement between simulated and data‐constrained upscaling results strongly suggests that anthropogenic sulfate trends have a small impact on carbon uptake in temperate forests due to scattered light.