Atmos. Chem. Phys. Discuss., 9, 2933-2965, 2009
www.atmos-chem-phys-discuss.net/9/2933/2009/
doi:10.5194/acpd-9-2933-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
A new physically-based quantification of isoprene and primary organic aerosol emissions from the world's oceans
B. Gantt, N. Meskhidze, and D. Kamykowski
North Carolina State University, Raleigh, North Carolina, USA

Abstract. The global marine sources of organic carbon (OC) are estimated here using a physically-based parameterization for the emission of marine isoprene and primary organic matter. The model developed in this study allowed us, for the first time, to explore the relative contributions of sub- and super-micron organic matter and phytoplankton-produced secondary organic aerosol (SOA) to the total OC fraction of marine aerosol. New laboratory measurements of isoprene production by some of the main phytoplankton species under a range of environmental conditions was scaled up, with the help of satellite products, to infer the total annual mean ocean isoprene emissions of 0.92 Tg C yr−1. The sensitivity studies using different schemes for the euphotic zone depth and ocean phytoplankton speciation produced the upper and the lower range of marine-isoprene emissions of 0.31 to 1.09 Tg C yr−1, respectively. Empirical relationships between fluxes of water soluble (WSOM) and water insoluble (WIOM) organic matter (OM) and chlorophyll-a concentration was used to estimate the total primary sources of oceanic sub- and super-micron OC of 1.26 and 19.01 Tg C yr−1, respectively. Using a fixed 3% mass yield for the conversion of isoprene to SOA, our model simulations show minor (less than 0.2%) contribution of ocean produced isoprene to the total marine source of OC. However, our model calculations also indicate that over the tropical waters, marine isoprene-derived SOA could contribute over 40% of the total monthly-averaged sub-micron OC fraction of marine aerosol. The estimated contribution of ocean-isoprene SOA to hourly averaged sub-micron marine OC fluxes is even higher, reaching nearly 100% over the vast regions of the oceans during the midday hours. As it is widely believed that cloud condensation nuclei (CCN) is typically dominated by sub-micron sized particles, our findings suggest that marine sources of SOA could play a critical role in modulating properties of shallow marine clouds and influencing the climate.

Citation: Gantt, B., Meskhidze, N., and Kamykowski, D.: A new physically-based quantification of isoprene and primary organic aerosol emissions from the world's oceans, Atmos. Chem. Phys. Discuss., 9, 2933-2965, doi:10.5194/acpd-9-2933-2009, 2009.
 
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