Preprints
https://doi.org/10.5194/bg-2022-250
https://doi.org/10.5194/bg-2022-250
 
17 Jan 2023
17 Jan 2023
Status: this preprint is currently under review for the journal BG.

Global analysis of the controls on seawater dimethylsulfide spatial variability

George Manville1, Thomas G. Bell2, Jane P. Mulcahy3, Rafel Simó4, Martí Galí4,5, Anoop S. Mahajan6, Shrivardhan Hulswar6, and Paul R. Halloran1 George Manville et al.
  • 1Faculty of Environment, Science and Economy, University of Exeter, Exeter, EX4 4PY, UK
  • 2Plymouth Marine Laboratory (PML), Plymouth, PL1 3DH, UK
  • 3Met Office, Exeter, EX1 3PB, UK
  • 4Institut de Ciències del Mar (ICM-CSIC), Barcelona, 08003, Catalonia, Spain
  • 5Barcelona Supercomputing Center (BSC-CNS), Barcelona, 08034, Catalonia, Spain
  • 6Indian Institute of Tropical Meteorology (IITM), Ministry of Earth Sciences, Pune, 411008, India

Abstract. Dimethylsulfide (DMS) emitted from the ocean makes a significant global contribution to natural marine aerosol and cloud condensation nuclei, and therefore our planet’s climate. Oceanic DMS concentrations show large spatiotemporal variability, but observations are sparse, so products describing global DMS distribution rely on interpolation or modelling. Understanding the mechanisms driving DMS variability, especially at local scales, is required to reduce uncertainty in large scale DMS estimates. We present a study of mesoscale and sub-mesoscale (<100 km) seawater DMS variability that takes advantage of the recent expansion in high frequency seawater DMS observations and uses all available data to investigate the typical distances over which DMS varies in all major ocean basins. These DMS spatial variability lengthscales (VLS) are uncorrelated with DMS concentrations. DMS concentrations and VLS can therefore be used separately to help identify mechanisms underpinning DMS variability. When data are grouped by sampling campaigns, almost 80 % of the DMS VLS can be explained using the VLS of sea surface height anomalies, density, and chlorophyll-a. Our global analysis suggests that both physical and biogeochemical processes play an equally important role in controlling DMS variability, in contrast with previous results based on data from the low–mid latitudes. The explanatory power of sea surface height anomalies indicates the importance of mesoscale eddies in driving DMS variability, previously unrecognised at a global scale and in agreement with recent regional studies. DMS VLS differs regionally, including surprisingly high frequency variability in low latitude waters. Our results independently confirm that relationships used in the literature to parameterise DMS at large scales appear to be considering the right variables. However, contrasts in regional DMS VLS highlight that important driving mechanisms remain elusive. The role of sub-mesoscale features should be resolved or accounted for in DMS process models and parameterisations. Future attempts to map DMS distributions should consider the length scale of variability.

George Manville et al.

Status: open (until 28 Feb 2023)

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George Manville et al.

George Manville et al.

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Short summary
We present the first global investigation of controls on seawater dimethylsulfide (DMS) spatial variability over scales up to 100 km. Sea surface height anomalies, density, and chlorophyll-a help explain almost 80 % of DMS variability. The results suggest that physical and biogeochemical processes play an equally important role in controlling DMS variability. These data provide independent confirmation that existing parameterisations of seawater DMS concentration use appropriate variables.
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