Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol S. R. Arnold1, D. V. Spracklen1, J. Williams2, N. Yassaa2,3, J. Sciare4, B. Bonsang4, V. Gros4, I. Peeken5, A. C. Lewis6, S. Alvain4, and C. Moulin4 1Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK 2Max Planck Institute for Chemistry, Mainz, Germany 3Now at Faculty of Chemistry, University of Sciences and Technology Houari Boumediene, U.S.T.H.B., Algiers, Algeria 4IPSL/LSCE, CEA Saclay, Gif-sur-Yvette, France 5Ifm GEOMAR, Kiel, Germany 6Department of Chemistry, University of York, York, UK
Abstract. We have combined the first satellite maps of the global
distribution of phytoplankton functional type and new measurements of
phytoplankton-specific isoprene productivities, with available remote marine
isoprene observations and a global model, to evaluate our understanding of the
marine isoprene source and its impacts on organic aerosol abundances. Using
satellite products to scale up data on phytoplankton-specific isoprene
productivity to the global oceans, we infer a mean "bottom-up" oceanic
isoprene emission of 0.31±0.08 (1σ) Tg/yr. By minimising the mean
bias between the model and isoprene observations in the marine atmosphere
remote from the continents, we produce a "top-down" oceanic isoprene source
estimate of 1.9 Tg/yr. We suggest our reliance on limited atmospheric
isoprene data, difficulties in simulating in-situ isoprene production rates in laboratory phytoplankton cultures,
and limited knowledge of isoprene production mechanisms across the broad range
of phytoplankton communities in the oceans under different environmental
conditions as contributors to this difference between the two estimates.
Inclusion of secondary organic aerosol (SOA) production from oceanic isoprene
in the model with a 2% yield produces small contributions (0.01–1.4%) to
observed organic carbon (OC) aerosol mass at three remote marine sites in the
Northern and Southern Hemispheres. Based on these findings we suggest an
insignificant role for isoprene in modulating remote marine aerosol
abundances, giving further support to a recently postulated primary OC source
in the remote marine atmosphere.
Citation: Arnold, S. R., Spracklen, D. V., Williams, J., Yassaa, N., Sciare, J., Bonsang, B., Gros, V., Peeken, I., Lewis, A. C., Alvain, S., and Moulin, C.: Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol, Atmos. Chem. Phys., 9, 1253-1262, doi:10.5194/acp-9-1253-2009, 2009.