Publication Date:
2013-11-08
Description:
Production pathways of the prominent volatile organic halogen compound methyl iodide (CH3I) are not fully understood. Previous model studies suggest either production via photochemical degradation of organic material or rather phytoplankton production. Correlations between biological and environmental variables derived from observations also suggest both production pathways. In this study we aim to address this question of source mechanisms with a global three-dimensional ocean general circulation model including biogeochemistry (MPIOM-HAMOCC) by carrying out a series of sensitivity experiments. Simulated distribution patterns and emissions of CH3I differ largely for the different production pathways. However, the evaluation of our model results with observations from a newly available global data set shows that observed surface concentrations of CH3I can be best explained by the photochemical production pathway. Our results further emphasize that correlations between CH3I and abiotic or biotic factors do not necessarily provide meaningful insights concerning the source of origin. Overall, we find a net global annual CH3I air–sea flux that ranges between 70 and 260 Gg yr−1. Hence, at the global scale the ocean is a net source of methyl iodide for the atmosphere, though in some regions in boreal winter fluxes are of opposite direction (from the atmosphere to the ocean).
Print ISSN:
1810-6277
Electronic ISSN:
1810-6285
Topics:
Biology
,
Geosciences
