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Diagnosing sea-surface dimethylsulfide (DMS) concentration from satellite data at global and regional scales

M. Galí,M. Levasseur,E. Devred,R. Simó,M. Babin

Published 2018 in Biogeosciences Discussions

ABSTRACT

The marine biogenic gas dimethylsulfide (DMS) can modulate regional and global climate by enhancing aerosol light scattering and seeding cloud formation. However, the lack of time- and space-resolved estimates of DMS concentration and emission hampers the assessment of its climatic effects. Here we present DMS SAT , a new remote sensing algorithm that relies on the nonlinear relationship between DMS, its phytoplanktonic precursor dimethylsulfoniopropioante (DMSPt) and plankton light exposure. The DMS SAT algorithm is computationally light and can be easily optimized for global and regional scales. At the global scale, it reproduces the main climatological features of DMS seasonality across contrasting biomes with remarkable skill compared to previous algorithms. Shortcomings of the global-scale optimized algorithm are the propagation of regional biases in remotely sensed chlorophyll (causing underestimation of DMS in the Southern Ocean) and the inability to reproduce high DMS/DMSPt ratios in late summer and fall in specific regions (which suggests the need to account for additional DMS drivers). Our work also highlights the shortcomings of interpolated DMS climatologies, caused by sparse and biased in situ sampling. Time series of DMS SAT between 2003–2016 in northern subpolar regions show wide interannual variability in the magnitude and timing of the annual DMS peak(s), demonstrating the need to move beyond the climatological view in studies of ocean-atmosphere interactions. By providing time- and space-resolved estimates of DMS emission, DMS SAT can leverage atmospheric chemistry and climate models and advance our understanding of plankton-aerosol-cloud interactions in the context of global change.

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