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

Abstract

Abstract. The marine biogenic gas dimethylsulfide (DMS) modulates 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 macroecological relationships between DMS, its phytoplanktonic precursor dimethylsulfoniopropionate (DMSPt) and plankton light exposure. In the first step, planktonic DMSPt is estimated from satellite-retrieved chlorophyll a and the light penetration regime as described in a previous study . In the second step, DMS is estimated as a function of DMSPt and photosynthetically available radiation (PAR) at the sea surface with an equation of the form: log 10 DMS = α+βlog 10 DMSPt+γ PAR. The two-step DMS SAT algorithm is computationally light and can be optimized for global and regional scales. Validation at the global scale indicates that DMS SAT has better skill than previous algorithms and reproduces the main climatological features of DMS seasonality across contrasting biomes. The main shortcomings of the global-scale optimized algorithm are related to (i) regional biases in remotely sensed chlorophyll (which cause underestimation of DMS in the Southern Ocean) and (ii) 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 derived from MODIS-Aqua in the subpolar North Atlantic between 2003 and 2016 show wide interannual variability in the magnitude and timing of the annual DMS peak(s), demonstrating the need to move beyond the classical climatological view. By providing synoptic time series 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.

Patterns and drivers of dimethylsulfide concentration in the northeast subarctic Pacific across multiple spatial and temporal scales

“…Only summertime data (defined here as June, July and August, JJA) falling within the NESAP region (44.5-61 • N, 180-120 • W) were included in this compilation. Although DMS concentrations and phytoplankton biomass often remain high through September (Galí et al, 2018;Lana et al, 2011;Steiner et al, 2012), there are fewer DMS data available for this month. Measurements were binned to a temporal sampling resolution of 1 min.…”

“…Increased DMS concentrations in the post-upwelling bloom phase may result from nitrogen limitation, increased grazing pressure (which releases DMSP into the dissolved pool; Simó et al, 2018), oxidative stress associated with shoaling mixed layers and a phytoplankton community shift towards high-DMSP-producing species (Nemcek et al, 2008;Franklin et al, 2009). Despite these advances in understanding DMS dynamics in the NESAP, many aspects of DMS cycling in this region remain poorly documented, including the factors influencing inter-annual variability (Steiner et al, 2012;Galí et al, 2018), the interplay between iron concentration and phytoplankton community shifts (Levasseur et al, 2006;Royer et al, 2010), and the relative importance of phytoplanktonic DMSP lyases and micrograzers (Steiner et al, 2012).…”

The quantitative role of microzooplankton grazing in dimethylsulfide (DMS) production in the NW Mediterranean

“…DMS concentrations are supersaturated in surface waters relative to the atmosphere, driving a global net sea-air flux of ca. 16-28 Tg S y −1 (Lana et al 2011;Galí et al 2018), one of the largest amongst marine organic volatiles (Carpenter et al 2012). In the atmosphere DMS is oxidized to molecules that either condense upon existing particles or nucleate to form new particles.…”

Dimethylsulfide (DMS), marine biogenic aerosols and the ecophysiology of coral reefs

“…Furthermore, if empirical relationships between coral physiological stress and DMS(P) biosynthesis can be deduced from field and laboratory experiments, a remotely sensed proxy for sea surface DMS concentrations and sea-air flux from coral reefs can be calculated (e.g. Cropp et al, 2018;Jones et al, 2007Jones et al, , 2018, similar to that produced for phytoplankton (Galí et al, 2018). Such proxies could be used in conjunction with long-term data on coral cover and health (e.g.…”