Potential sensitivity of photosynthesis and isoprene emission to direct radiative effects of atmospheric aerosol pollution
A global Earth system model is applied to quantify the impacts of direct anthropogenic aerosol effective radiative forcing on gross primary productivity (GPP) and isoprene emission. The impacts of different pollution aerosol sources (anthropogenic, biomass burning, and non-biomass burning) are i...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/4213/2016/acp-16-4213-2016.pdf |
| Summary: | A global Earth system model is applied to quantify the impacts of direct
anthropogenic aerosol effective radiative forcing on gross primary
productivity (GPP) and isoprene emission. The impacts of different pollution
aerosol sources (anthropogenic, biomass burning, and non-biomass burning) are
investigated by performing sensitivity experiments. The model framework
includes all known light and meteorological responses of photosynthesis, but
uses fixed canopy structures and phenology. On a global scale, our results
show that global land carbon fluxes (GPP and isoprene emission) are not
sensitive to pollution aerosols, even under a global decline in surface solar
radiation (direct + diffuse) by ∼ 9 %. At a regional scale,
GPP and isoprene emission show a robust but opposite sensitivity to pollution
aerosols in regions where forested canopies dominate. In eastern North
America and Eurasia, anthropogenic pollution aerosols (mainly from
non-biomass burning sources) enhance GPP by +5–8 % on an annual
average. In the northwestern Amazon Basin and central Africa, biomass burning
aerosols increase GPP by +2–5 % on an annual average, with a peak
in the northwestern Amazon Basin during the dry-fire season
(+5–8 %). The prevailing mechanism varies across regions: light
scattering dominates in eastern North America, while a reduction in direct
radiation dominates in Europe and China. Aerosol-induced GPP productivity
increases in the Amazon and central Africa include an additional positive
feedback from reduced canopy temperatures in response to increases in canopy
conductance. In Eurasia and northeastern China, anthropogenic pollution
aerosols drive a decrease in isoprene emission of −2 to −12 % on
an annual average. Future research needs to incorporate the indirect effects
of aerosols and possible feedbacks from dynamic carbon allocation and
phenology. |
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| ISSN: | 1680-7316 1680-7324 |