Preprints
https://doi.org/10.5194/egusphere-2024-173
https://doi.org/10.5194/egusphere-2024-173
27 Feb 2024
 | 27 Feb 2024
Status: this preprint is open for discussion.

Dimethyl sulfide (DMS) climatologies, fluxes and trends – Part A: Differences between seawater DMS estimations

Sankirna D. Joge, Anoop Sharad Mahajan, Shrivardhan Hulswar, Christa Marandino, Martí Galí, Thomas Bell, and Rafel Simo

Abstract. Dimethyl sulfide (DMS) is a naturally emitted trace gas that can affect the Earth's radiative budget by changing cloud albedo. Most models depend on regional or global distributions of seawater DMS concentrations and sea-air flux parameterizations to estimate its emissions. In this study, we analyze the differences between three estimations of seawater DMS, one of which is an observation-based interpolation method (Hulswar et al., 2022 (hereafter referred to as H22)) and two are proxy-based parameterization methods (Galí et al., 2018a (G18); Wang et al., 2020 (W20)). The interpolation-based method depends on the distribution of observations and the methods used to fill data between observations, while the parameterization-based methods rely on establishing a relationship between DMS and environmental parameters such as chlorophyll a, mixed layer depth, nutrients, sea surface temperature, etc., which can then be used to predict DMS concentrations. On average, the interpolation-based methods show higher DMS values compared to the parameterization-based methods. Even though the interpolation method shows higher values than the parameterization-based methods, it fails to capture mesoscale variability. The regression-based parameterization method (G18) shows the lowest values compared to other estimations, especially in the Southern Ocean, which is the high DMS region in Austral summer. The parameterization-based methods suggest significant positive long-term trends in seawater DMS (6.94 ±1.44 % decade-1 for G18 and 3.53 ±0.53 % decade-1 for W20). Since large differences, often more than 100 %, are observed between the different estimations of seawater DMS, the derived sea-air fluxes and hence the impact of DMS on the radiative budget are very sensitive to the estimate used.

Sankirna D. Joge, Anoop Sharad Mahajan, Shrivardhan Hulswar, Christa Marandino, Martí Galí, Thomas Bell, and Rafel Simo

Status: open (until 12 May 2024)

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Sankirna D. Joge, Anoop Sharad Mahajan, Shrivardhan Hulswar, Christa Marandino, Martí Galí, Thomas Bell, and Rafel Simo
Sankirna D. Joge, Anoop Sharad Mahajan, Shrivardhan Hulswar, Christa Marandino, Martí Galí, Thomas Bell, and Rafel Simo

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Short summary
Dimethyl sulfide (DMS) is the largest natural source of sulfur into the atmosphere and leads to the formation of CCN. DMS emissions, and hence the quantification of its impacts, have large uncertainties, but a detailed study on the range of emissions and drivers of their uncertainty is missing to date. The emissions are usually calculated from the seawater DMS concentrations and a flux parameterization. Here we quantify the differences in DMS seawater products, which can affect the DMS fluxes.