Booge, Dennis, Schlundt, Cathleen , Bracher, Astrid, Endres, Sonja , Zäncker, Birthe, Stadtler, Scarlet and Marandino, Christa A. (2018) Marine Isoprene: From Surface Ocean Production to Atmospheric SOA Formation. [Talk] In: Ocean Sciences Meeting 2018. , 11.-16.02.2018, Portland, Oregon, USA .

Abstract

Isoprene, a biogenic trace gas produced both on land and in the ocean, is an important precursor of secondary organic aerosol (SOA). Although the marine source of isoprene to the atmosphere is smaller than the land source, it may still be important for SOA formation on regional scales especially in the remote marine boundary layer. Surface ocean isoprene parameterizations are numerous, but as only a few studies have measured isoprene directly in the surface ocean the understanding of source/sink processes is lacking.
Here we present isoprene and related field measurements in the mixed layer from the Indian Ocean and the East Pacific Ocean to investigate the production and consumption rates in two contrasting regions, namely oligotrophic open ocean and coastal upwelling region. Our data show that the ability of different phytoplankton functional types (PFTs) to produce isoprene seems to be mainly influenced by light, ocean temperature, and salinity. Our field measurements also demonstrate that nutrient availability seems to have a direct influence on the isoprene production. With the help of pigment data, we calculate in-field isoprene production rates for different PFTs under varying biogeochemical and physical conditions. Using these new calculated production rates we demonstrate that an additional, significant and variable loss, besides a known chemical loss and a loss due to air sea gas exchange, is needed to explain the measured isoprene concentrations. Using these field derived rates, together with measured oceanic isoprene concentrations, it is possible to evaluate global marine isoprene emissions. These emissions are implemented into an atmospheric chemistry climate model (ECHAM-HAMMOZ) in order to estimate the importance of marine derived isoprene as a precursor to SOA formation over the remote ocean.

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