Quantifying global marine isoprene fluxes using MODIS chlorophyll observations

We report global distributions of marine isoprene flux, whose source is estimated by combining an empirical relationship for isoprene production rate with MODIS satellite chlorophyll observations from 2001. We use a steady-state water column model including losses to chemistry, bacteria, and air-sea exchange. Physical mixing is a negligible sink. Flux estimates range from 10(7) 10(9) molecules cm(-2) s(-1), with considerable spatial and temporal variability, resulting in a global annual total of 0.1 Tg C/yr. Air-sea exchange is the dominant isoprene sink in the surface oceans, with bacteria the second largest, but much less important, sink. The reported fluxes represent a small loss of OH in the remote marine boundary layer (MBL) compared to other oxidants. Application of our approach to other reactive compounds may improve a priori flux estimates for coupled atmosphere-ocean biogeochemistry inverse model studies.