Dimethylsulfide Concentrations Research Articles

Nested cross-validation Gaussian process to model dimethylsulfide mesoscale variations in warm oligotrophic Mediterranean seawater

The study proposes an approach to elucidate spatiotemporal mesoscale variations of seawater Dimethylsulfide (DMS) concentrations, the largest natural source of atmospheric sulfur aerosol, based on the Gaussian Process Regression (GPR) machine learning model. Presently, the GPR was trained and evaluated by nested cross-validation across the warm-oligotrophic Mediterranean Sea, a climate hot spot region, leveraging the high-resolution satellite measurements and Mediterranean physical reanalysis together with in-situ DMS observations. The end product is daily gridded fields with a spatial resolution of 0.083° × 0.083° (~9 km) that spans 23 years (1998–2020). Extensive observations of atmospheric methanesulfonic acid (MSA), a typical biogenic secondary aerosol component from DMS oxidation, are consistent with the parameterized high-resolution estimates of sea-to-air DMS flux (FDMS). This represents substantial progress over existing coarse-resolution DMS global maps which do not accurately depict the seasonal patterns of MSA in the Mediterranean atmospheric boundary layer.

Data collation for climate-cooling gas dimethylsulfide in Antarctic snow, sea ice and underlying seawater

Dimethylsulfide (DMS) is a climatically active volatile sulfur compound found in Earth’s oceans and atmosphere that plays an important role in cloud formation. DMS originates from its precursor dimethylsulfoniopropionate (DMSP), which is produced by several classes of phytoplankton. Concentrations of DMS and DMSP in Antarctic sea ice, snow and underlying seawater are not well documented and there is currently no dataset available to find the existing data. The purpose of this project was to compile historical measurements into a publicly available dataset. A total of 220 samples collected since 1992 were compiled using the Antarctic Sea ice Processes and Climate program template, in accordance with the existing datasets for chlorophyll-a, macronutrients, and dissolved iron. Analyses performed on the completed DMS dataset showed that the spatial and temporal coverages are limited; there are barely any measurements in autumn and winter, nor in the Amundsen or Ross seas. These findings provide a basis for future sampling efforts in the Antarctic region.

Impact of Long-term Fasting on Breath Volatile Sulphur Compounds, Inflammatory Markers and Saliva Microbiota Composition.

Despite substantial evidence supporting the role of resident bacterial communities in therapeutic fasting outcomes, research has primarily focused on gut microbiota, leaving changes in oral microbiota largely unexplored. The clinical significance of oral health changes during fasting is nonetheless underscored by the documented development of halitosis in fasting individuals. However, no scientific studies have comprehensively examined the interplay between salivary microbiota alterations, inflammatory changes in the gingival crevice, and the production of malodorous volatile compounds. We examined volatile sulphur compounds (VSC) in breath during fasting, cytokine levels in the gingival crevice, and oral microbiota composition of the saliva in a single-arm interventional study involving 36 subjects who fasted for 10 ± 3 days. Participants fasted according to Buchinger fasting guidelines. VSC were evaluated every morning before any food or drink intake using the OralChroma gas chromatography device. Saliva and gingival crevicular fluid (GCF) samples were collected at the clinical site before fasting, at the end of fasting, and at the end of food reintroduction. Follow-up saliva samples were sent to the patients after 1 and 3 months. Saliva samples were processed and analysed by targeted sequencing of 16S rRNA gene amplicons, whereas the expression of 6 inflammatory markers in the GCF were analysed using a multiplex fluorescent bead-based immunoassay. The quantification of volatile compounds in the breath demonstrated a statistically significant increase in dimethylsulfide levels during fasting, which corroborates the occurrence of bad breath as a common side effect of fasting. Salivary microbiota profiling showed a shift in microbial composition, including reduction in the levels of Neisseria, Gemella and Porphyromonas spp., concomitant with an increase in the levels of Megasphaera, Dialister, Prevotella, Veillonella, Bifidobacteria, Leptotrichia, Selenomonas, Alloprevotella, and Atopobium. We further demonstrated a reduction in the levels of the pro-inflammatory cytokine interleukin-8 in the GCF. Dimethylsulfide concentrations in the breath increased during fasting, and this was correlated to changes in the oral microbiota. Future studies are needed to illuminate the possible impact of these changes on oral and general health status.

Dimethyl sulfide (DMS) climatologies, fluxes, and trends – Part 1: Differences between seawater DMS estimations

Abstract. Dimethyl sulfide (DMS) is a naturally emitted trace gas that can affect the Earth's radiative budget by changing cloud albedo. Most atmospheric models that represent aerosol processes depend on regional or global distributions of seawater DMS concentrations and sea–air flux parameterizations to estimate its emissions. In this study, we analyse the differences between three estimations of seawater DMS, one of which is an observation-based interpolation method following Hulswar et al. (2022) (hereafter referred to as H22) and two of which are proxy-based parameterization methods following Galí et al. (2018) (hereafter referred to as G18) and Wang et al. (2020a) (hereafter referred to as 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 positive long-term trends in seawater DMS (3.82±0.79 % per decade for G18 and 2.13±0.32 % per decade 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 sensitive to the estimate used.

Dimethyl sulfide (DMS) climatologies, fluxes, and trends – Part 2: Sea–air fluxes

Abstract. Dimethyl sulfide (DMS) contributes to cloud condensation nuclei (CCN) formation in the marine environment. DMS is ventilated from the ocean to the atmosphere, and, in most models, this flux is calculated using seawater DMS concentrations and a sea–air flux parameterization. Here, climatological seawater DMS concentrations from interpolation and parameterization techniques are passed through seven flux parameterizations to estimate the DMS flux. The seasonal means of calculated fluxes are compared to identify differences in absolute values and spatial distributions, which show large differences depending on the flux parameterization used. In situ flux observations were used to validate the estimated fluxes from all seven parameterizations. Even though we see a correlation between the estimated and observation values, all methods underestimate the fluxes in the higher range (>20 µmol m−2 d−1) and overestimate the fluxes in the lower range (<20 µmol m−2 d−1). The estimated uncertainty in DMS fluxes is driven by the uncertainty in seawater DMS concentrations in some regions but by the choice of flux parameterization in others. We show that the resultant flux is, hence, highly sensitive to both and suggest that there needs to be an improvement in the estimation methods of global seawater DMS concentration and sea–air fluxes for accurately modeling the effect of DMS on the atmosphere.

Regulation of freshwater filamentous green algae (Cladophora) and its impact on malodorous volatile organic sulfur compound (DMS) by biomanipulation

When improving the water quality of natural bodies such as lakes, the explosive growth of filamentous green alga Cladophora can limit the growth of submerged macrophytes and prevent the water from shifting to a clear state. During the decay of Cladophora, it can cause various water quality issues such as reduced dissolved oxygen, increased nutrient levels and water odor. Biomanipulation, involving the introduction of a suitable density of aquatic animals into the water, can reduce the biomass of filamentous algae. We hypothesized that stocking appropriate densities of aquatic animals could reduce filamentous algal biomass and at the same time reduce the concentration of odorants in the water. Our study investigated the impact of stocking swamp shrimp (Macrobrachium nipponense), rosy bitterling (Rhodeus ocellatus), and silver carp (Hypophthalmichthys molitrix) at low (30 g/m3), medium (60 g/m3) and high (120 g/m3) densities on water quality, biomass of primary producers (such as Cladophora, submerged macrophyte and algae) and malodorous volatile organic sulfur compound dimethyl sulfide (DMS) in the water, respectively. It was found that the swamp shrimp treatment groups and the rosy bitterling high-density groups effectively inhibited the growth of filamentous green algae cover, in which the rosy bitterling high-density group reduced the filamentous green algae mat coverage by 29.65 % compared with the control group. Additionally, the high-density swamp shrimp and rosy bitterling groups notably promoted the growth of submerged macrophytes (Vallisneria denseserrulata), and significantly reduced the concentration of the malodorous DMS in the water. Overall, stocking swamp shrimp and rosy bitterling can benefit the restoration of aquatic ecology and the maintenance of clear water. However, it is essential to consider potential changes in water quality resulting from excessive stocking density. Therefore, the appropriate density and proportion of stocking should be determined in conjunction with the specific scale of the aquatic ecological restoration project.

Sex-Specific Lipid Profiles and Flavor Volatiles in Giant Salamander (Andrias davidianus) Tails Revealed by Lipidomics and GC-IMS

To elucidate the relationships between lipid components and odor traits, this study comparatively characterized the distinct lipid compositions and flavor volatiles in giant salamander tails of different sexes via mass-spectrometry-based lipidomics and GC-IMS. A total of 3145 fat metabolites were detected in male and female giant salamander tails, with the largest contributors being triglycerides (TGs, 840) and phosphatidylcholines (PCs, 383). Notably, the contents of PCs and TGs were greater in female tails than in male tails, and the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were also greater in the female group. Additionally, a total of 45 volatile components were detected, namely, 14 aldehydes, 14 alcohols, 9 ketones, 3 acids, 3 esters, 1 ether, and 1 amine. Alcohols (29.96% to 34.85%) and aldehydes (21.07% to 22.75%) were the predominant volatiles. Multivariate statistical analysis revealed 22 key differential fats and 26 differential odor substances as distinguishing labels between sexes. Correlation analysis revealed that the concentrations of triethylamine, dimethyl sulfide, ethanol-D, and 3-methyl butanal-D were significantly positively correlated with the concentrations of diglyceride (DG) (26:6e), cardiolipin (CL) (59:4), acylcarnitine (AcCa) (22:4), and triglyceride (TG) (52:10) (p < 0.01). Threefold cross-validation revealed that the prediction accuracies of these differential lipids and volatile compounds for sex recognition via the random forest model were 100%. These findings might not only provide insight into the effects of sexes on the lipid and volatile profiles of giant salamander tails but also provide clues for their gender recognition.

A 20-year (1998–2017) global sea surface dimethyl sulfide gridded dataset with daily resolution

Abstract. The oceanic emission of dimethyl sulfide (DMS) plays a vital role in the Earth's climate system and constitutes a substantial source of uncertainty when evaluating aerosol radiative forcing. Currently, the widely used monthly climatology of sea surface DMS concentration falls short of meeting the requirement for accurately simulating DMS-derived aerosols with chemical transport models. Hence, there is an urgent need for a high-resolution, multi-year global sea surface DMS dataset. Here we develop an artificial neural network ensemble model that uses nine environmental factors as input features and captures the variability of the DMS concentration across different oceanic regions well. Subsequently, a global sea surface DMS concentration and flux dataset (1° × 1°) with daily resolution spanning from 1998 to 2017 is established. According to this dataset, the global annual average concentration was ∼ 1.71 nM, and the annual total emissions were ∼ 17.2 Tg S yr−1, with ∼ 60 % originating from the Southern Hemisphere. While overall seasonal variations are consistent with previous DMS climatologies, notable differences exist in regional-scale spatial distributions. The new dataset enables further investigations into daily and decadal variations. Throughout the period 1998–2017, the global annual average concentration exhibited a slight decrease, while total emissions showed no significant trend. The DMS flux from our dataset showed a stronger correlation with the observed atmospheric methanesulfonic acid concentration compared to those from previous monthly climatologies. Therefore, it can serve as an improved emission inventory of oceanic DMS and has the potential to enhance the simulation of DMS-derived aerosols and associated radiative effects. The new DMS gridded products are available at https://doi.org/10.5281/zenodo.11879900 (Zhou et al., 2024).

Summer sea ice melting enhances phytoplankton and dimethyl sulfide production

AbstractThe relationships among sea ice melting, phytoplankton assemblages, and the production of climate‐relevant trace gases in the Southern Ocean are gaining increasing attention from the scientific community. This is particularly true for dimethyl sulfide (DMS), which plays an important role in atmospheric chemistry by influencing the formation of sulfated aerosols with radiative impacts and constituting cloud condensation nuclei. In the current study, chlorophyll a (Chl a), DMS and its precursors dimethylsulfoniopropionate (DMSP), were quantified in the Weddell–Scotia Confluence (WSC) during the 2018 record ice extent minimum period. Mixed layer changes were found to be generally associated with spatial variation in sea ice melt, with the depth being six times deeper in ice‐free, well‐mixed regions than in seasonal ice‐melting zones. The surface Chl a concentration increased from ice‐free to ice‐melting regions with elevated sea ice meltwater percentages and drawdown surface nutrient concentrations. The concentrations of surface and depth‐integrated Chl a in the upper 150 m reached maxima in the ice‐melting region with the highest fraction of sea ice meltwater, illustrating that sea ice melting promoted the occurrence of phytoplankton blooms. The DMS and DMSP concentrations in the vicinity of the ice‐melting zone were approximately three times higher than those in the ice‐free waters. The observations of this study show that the regions of ice melting in the WSC were a zone of particularly high sea–air fluxes of DMS, which could significantly contribute to the atmospheric budget of DMS in the polar regions.

Factors Controlling DMS Emission and Atmospheric Sulfate Aerosols in the Western Pacific Continental Sea

AbstractThe western Pacific continental sea significantly influences the regulation of climate‐active gases budget and the burden of sulfate aerosols. An underway shipboard measurement device was used to determine the dimethyl sulfide (DMS) in the surface seawater and overlying atmosphere in the East China Continental Sea. The average concentration of DMS in atmosphere and seawater was 122.8 ± 86.2pptv and 6.47 ± 3.58 nmol L−1, respectively. The variation trend of surface water DMS in the western Pacific continental sea was influenced by the abundance and composition of phytoplankton under different ocean current systems, with a significant impact from eddies on DMS production in the South China Sea. By eliminating the influence of terrestrial sources and limiting air mass transport within the marine boundary layer, strong correlations were established between atmospheric DMS and air mass exposure to chlorophyll (Echl), as well as between aerosol methanesulfonic acid (MSA) and Echl. During the aerosol sampling period, the atmospheric DMS levels (1,057 ± 371 ng/m3) were significantly higher than MSA levels (46.3 ± 59.8 ng/m3) in the East China Sea, where the conversion of DMS to MSA was not affected by changes in DMS concentration. The sea‐to‐air fluxes of DMS varied over a wide range, from 0.02 to 156.0 μmol m−2 d−1, with an average of 14.35 ± 18.58 μmol m−2 d−1. Marine DMS emissions play a critical role in the formation of sulfur aerosols on the western Pacific continental shelf, accounting for 24.6 ± 7.6% (14.8%–37.8%) of the total sulfate aerosols.

Characterizing spatio-temporal variations of dimethyl sulfide in the Yellow and East China Sea based on BP neural network

Dimethyl sulfide (DMS), an organic volatile sulfide produced from Dimethylsulfoniopropionate (DMSP), exerts a significant impact on the global climate change. Utilizing published literature data spanning from 2005 to 2020, a BP neural network (BPNN) model of the surface seawater DMS in the Yellow and East China Sea (YECS) was developed to elucidate the influence of various marine factors on the DMS cycle. Results indicated that the six parameters inputted BPNN model, that include the time (month), latitude and longitude, sea-surface chlorophyll a (Chl-a), sea-surface temperature (SST), and sea-surface salinity (SSS), yielded the optimized simulation results (R2 = 0.71). The optimized estimation of surface seawater DMS in the YECS were proved to be closely aligned with the observed data across all seasons, which demonstrated the model’s robust applicability. DMS concentration in surface seawater were found to be affected by multiple factors such as Chl-a and SST. Comparative analysis of the three environmental parameters revealed that Chl-a exhibited the most significant correlation with surface seawater DMS concentration in the YECS (R2 = 0.20). This underscores the pivotal role of chlorophyll in phytoplankton photosynthesis and DMS production, emphasizing its importance as a non-negligible factor in the study of DMS and its sulfur derivatives. Furthermore, surface seawater DMS concentration in the YECS exhibited positive correlations with Chl-a and SST, while displaying a negative correlation with SSS. The DMS concentration in the YECS show substantial seasonal variations, with the maximum value (5.69 nmol/L) in summer followed in decreasing order by spring (3.96 nmol/L), autumn (3.18 nmol/L), and winter (1.60 nmol/L). In the YECS, there was a gradual decrease of DMS concentration from the nearshore to the offshore, especially with the highest DMS concentration concentrated in the Yangtze River Estuary Basin and the south-central coastal part off the Zhejiang Province. Apart from being largely composed by the release of large amounts of nutrients from anthropogenic activities and changes in ocean temperature, the spatial and temporal variability of DMS may be driven by additional physicochemical parameters.

Spatial distribution and environmental/biological co-regulation mechanism of dimethyl sulfur compounds in the eastern Indian Ocean

Dimethyl sulfur compounds including dimethylsulfoniopropionate (DMSP), dimethyl sulfide (DMS), and dimethyl sulfoxide (DMSO), play a crucial part in global sulfur cycling. The eastern Indian Ocean (EIO), characterized by its remarkable diversity of biomes and climate dynamics, is integral to global climate regulation. However, the regulation mechanism of DMS (P, O) in the EIO remains to be elucidated in detail. This paper presented a field survey aimed at investigating the spatial distribution of DMS (P, O) and their relationships with environmental and biological factors in the EIO. The surface concentrations of DMS, DMSPt, and DMSOt varied from 0.07 to 7.37 nmol/L, 0.14 to 9.17 nmol/L, and 0.15 to 3.32 nmol/L, respectively, and their distributions are attributed to high Chl-a concentration near Sri Lanka and the influence of ocean currents (Wyrtki jets, Bay of Bengal runoff). Higher concentrations of DMS (P) and DMSOt were predominantly observed in water columns shallower than 75m and deeper than 75m deep, respectively. The monthly DMS fluxes in the study area peaked in August. Temperature and Dissolved Silica Index (DSI) were the key environmental determinants for DMS distribution, while nitrate (NO3-) was the primary factor for both DMSPt and DMSOt. In terms of biological factors, Prochlorococcus and Synechococcus were significant contributors to DMS (P, O) dynamics. Synechococcus was the dominant influence on the DMS source and DMSPt sink, whereas Prochlorococcus primarily consumed DMSOt. Furthermore, the structural equation modeling (SEM) revealed the relationship between DMS, DMSPt, DMSOt, and the key environmental/biological factors, as well as among them, and together they formed a co-regulatory network in the EIO. This contributes significantly to the advancement of global ecosystem models for DMS (P, O).

Effect of removing bacteria and dissolved organic matter on DMS production in Nannochloropsis oceanica concentrates

The aim of this study was to determine the influence of bacteria and organic matter on the occurrence of dimethyl sulfide (DMS) over the shelf life of Nannochloropsis oceanica concentrates. Two concentrates were compared: Control treatment, composed of biomass collected by centrifugation and diluted to a cell density of 5 × 109 cells·mL−1, and a washed concentrate treatment, where the biomass underwent successive centrifugations to remove dissolved organic matter (DOM) and bacteria before being diluted to a cell density of 5 × 109 cells·mL−1. Both concentrates were stored at two temperatures: 23 °C for 10 days and 4 °C for 85 days. Cellular viability, bacterial density, DOM, and DMS concentration were assessed. The washing process was responsible for removing approximately 84 % of the bacterial load from the concentrates. This significant reduction played a crucial role in decreasing the concentrations of DOM and DMS over the storage period. Furthermore, the process did not impair the cellular viability of microalgae. The findings underscore the importance of carefully managing bacterial and organic components in microalgal concentrates, especially when considering the preservation of freshness and cellular viability, which are key factors in applications such as larviculture.

How far does feedback on oral malodor assessment influence the decision to quit smoking?

A retrospective, uncontrolled, questionnaire-based, pre-post study involving adult male smoker volunteers who were invited to attend a one-day smoking cessation event at their workplace. To assess the effect of feedback on motivation for smoking cessation using oral-malodor measurements. At baseline, the participants attended a brief video presentation regarding various oral health-specific effects of smoking, joined a group introduction to smoking-cessation aids, and were given questionnaires that inquired information about smoking status including type, daily consumption, and duration. Subsequently, respiratory function and oral-malodor assessment were conducted using exhaled and oral cavity air, respectively. To measure oral-malodor, hydrogen sulfide, methyl mercaptan, and dimethyl sulfide concentrations were determined. Participants' intention for smoking cessation was evaluated through questionnaire before and after the event, classifying their intentions as aiming to quit within the next month, within the next 6 months, or having no intention to quit smoking. Immediate feedback on respiratory function and oral malodor measurements was provided by medical and dental blinded examiners, respectively. A total of 241 men, aged 20-54 years, were enrolled and included:169 (70.1%) exclusive cigarette smokers, 39 (16.2%) exclusive heated-tobacco product users, and 33 (13.7%) users of both. Prior to the health event, 8.7%, 17.0%, and 74.3% of smokers expressed intentions to quit within the next month, the next 6 months, or had no intention to quit, respectively. After the event, the corresponding percentages shifted to 17.8%, 26.6%, and 55.6%. In multivariable logistic regression analysis, the association with intention to quit in the next month was significant only for methyl mercaptan concentration in oral cavity air, with an adjusted odds ratio (AOR) of 4.24 (95% CI: 1.52-11.84; p = 0.006). Sensitivity analysis revealed that this association was concentration-dependent. On the other hand, higher daily tobacco consumption (≥ 15 pieces) was significantly associated with less likely intention to quit in the next 6 months (AOR = 0.37; 95% CI: 0.15-0.92, p = 0.032). Feedback on oral malodor measurement may support the motivation of men to quit smoking within the next month, rather than waiting for the next 6 months.

Observationally constrained analysis of sulfur cycle in the marine atmosphere with NASA ATom measurements and AeroCom model simulations

Abstract. The atmospheric sulfur cycle plays a key role in air quality, climate, and ecosystems, such as pollution, radiative forcing, new particle formation, and acid rain. In this study, we compare the spatially and temporally resolved measurements from the NASA Atmospheric Tomography (ATom) mission with simulations from five AeroCom III models for four sulfur species (dimethyl sulfide (DMS), sulfur dioxide (SO2), particulate methanesulfonate (MSA), and particulate sulfate (SO4)). We focus on remote regions over the Pacific, Atlantic, and Southern oceans from near the surface to ∼ 12 km altitude range covering all four seasons. In general, the differences among model results can be greater than 1 order of magnitude. Comparing with observations, model-simulated SO2 is generally low, whereas SO4 is generally high. Simulated DMS concentrations near the sea surface exceed observed levels by a factor of 5 in most cases, suggesting potential overestimation of DMS emissions in all models. With GEOS model simulations of tagging emission from anthropogenic, biomass burning, volcanic, and oceanic sources, we find that anthropogenic emissions are the dominant source of sulfate aerosol (40 %–60 % of the total amount) in the ATom measurements at almost all altitudes, followed by volcanic emissions (18 %–32 %) and oceanic sources (16 %–32 %). Similar source contributions can also be derived at broad ocean basins and on monthly scales, indicating the representativeness of ATom measurements for global ocean. Our work presents the first assessment of AeroCom sulfur study using ATom measurements, providing directions for improving sulfate simulations, which remain the largest uncertainty in radiative forcing estimates in aerosol climate models.

Changes in global DMS production driven by increased CO2 levels and its impact on radiative forcing

Our study highlights the importance of understanding the future changes in dimethyl-sulfide (DMS), the largest natural sulfur source, in the context of ocean acidification driven by elevated CO2 levels. We found a strong negative correlation (R2 = 0.89) between the partial pressure of carbon dioxide (pCO2) and sea-surface DMS concentrations based on global observational datasets, not adequately captured by the Coupled Model Intercomparison Project Phase 6 (CMIP6) Earth System Models (ESMs). Using this relationship, we refined projections of future sea-surface DMS concentrations in CMIP6 ESMs. Our study reveals a decrease in global sea-surface DMS concentrations and the associated aerosol radiative forcing compared to ESMs’ results. These reductions represent ~9.5% and 11.1% of the radiative forcings resulting from aerosol radiation and cloud interactions in 2100 reported by the Intergovernmental Panel on Climate Change Sixth Assessment Report. Thus, future climate projections should account for the climate implications of changes in DMS production due to ocean acidification.

Spatial and seasonal variability in volatile organic sulfur compounds in seawater and the overlying atmosphere of the Bohai and Yellow seas

Abstract. Volatile organic sulfur compounds (VSCs), including carbon disulfide (CS2), dimethyl sulfide (DMS), and carbonyl sulfide (COS), were surveyed in the seawater of the Bohai and Yellow seas and the overlying atmosphere during spring and summer of 2018 to understand the production and loss of VSCs and their influence factors. The concentration ranges of COS, DMS, and CS2 in the surface seawater were 0.14–0.42, 0.41–7.74, and 0.01–0.18 nmol L−1 during spring and 0.32–0.61, 1.31–18.12, and 0.01–0.65 nmol L−1 during summer, respectively. The COS concentrations exhibited positive correlation with dissolved organic carbon (DOC) concentrations in seawater during summer, which verified the photochemical production of COS from chromophoric dissolved organic matter (CDOM). High DMS concentrations occurred near the Yellow River, Laizhou Bay, and Yangtze River estuary, coinciding with high nitrate and chlorophyll (Chl) a concentrations due to river discharge during summer. The COS, DMS, and CS2 concentrations were the highest in the surface seawater and decreased with the depth. The mixing ratios of COS, DMS, and CS2 in the atmosphere were 255.9–620.2, 1.3–191.2, and 5.2–698.8 pptv during spring and 394.6–850.1, 10.3–464.3, and 15.3–672.7 pptv in summer, respectively. The ratios of mean oceanic concentrations and atmospheric mixing ratios for summer to spring in COS, DMS, and CS2 were 1.8, 3.1, 3.7 and 1.6, 4.6, 1.5, respectively. The ratios of the mean sea-to-air fluxes for summer to spring in COS, DMS, and CS2 were 1.2, 2.1, and 4.3. The sea-to-air fluxes of VSCs indicated that the marginal seas are important sources of VSCs in the atmosphere. The results support a better understanding of the contribution of VSCs in marginal seas.

The sensitivity of Southern Ocean atmospheric dimethyl sulfide (DMS) to modeled oceanic DMS concentrations and emissions

Abstract. The biogeochemical formation of dimethyl sulfide (DMS) from the Southern Ocean is complex, dynamic, and driven by physical, chemical, and biological processes. Such processes, produced by marine biogenic activity, are the dominant source of sulfate aerosol over the Southern Ocean. Using an atmosphere-only configuration of the United Kingdom Earth System Model (UKESM1-AMIP), we performed eight 10-year simulations for the recent past (2009–2018) during austral summer. We tested the sensitivity of atmospheric DMS to four oceanic DMS datasets and three DMS transfer velocity parameterizations. One oceanic DMS dataset was developed here from satellite chlorophyll a. We find that the choice of oceanic DMS dataset has a larger influence on atmospheric DMS than the choice of DMS transfer velocity. Simulations with linear transfer velocity parameterizations show a more accurate representation of atmospheric DMS concentration than those using quadratic relationships. This work highlights that the oceanic DMS and DMS transfer velocity parameterizations currently used in climate models are poorly constrained for the Southern Ocean region. Simulations using oceanic DMS derived from satellite chlorophyll a data, and when combined with a recently developed linear transfer velocity parameterization for DMS, show better spatial variability than the UKESM1 configuration. We also demonstrate that capturing large-scale spatial variability can be more important than large-scale interannual variability. We recommend that models use a DMS transfer velocity parameterization that was developed specifically for DMS and improvements to oceanic DMS spatial variability. Such improvements may provide a more accurate process-based representation of oceanic and atmospheric DMS, and therefore sulfate aerosol, in the Southern Ocean region.

Ice Cloud Formation Related to Oceanic Supply of Ice‐Nucleating Particles: A Case Study in the Southern Ocean Near an Atmospheric River in Late Summer

AbstractThis study investigated ice cloud formation associated with marine bioaerosols over the Southern Ocean (SO) using a combination of cloud particle sensor (CPS) sonde observations, satellite products, reanalysis data, and backward trajectory analysis. The CPS sonde detected ice clouds at temperatures higher than −10°C in the mid‐troposphere near an atmospheric river at high‐latitudes over the SO. Backward trajectory analyses indicated that a mid‐latitude air mass with a high concentration of atmospheric dimethylsulfide (DMS) in the atmospheric boundary layer (<1 km) arrived at the ice cloud formation layer over the high‐latitudes. The DMS in the boundary layer began to increase under high wave conditions, coincident with the highest chlorophyll‐a concentrations in the ocean. These results suggest that bioaerosols emitted from the ocean over the mid‐latitudes acted as ice‐nucleating particles for ice cloud formation over high‐latitudes.

Effect of PAR irradiance intensity on Phaeocystis antarctica (Prymnesiophyceae) growth and DMSP, DMSO, and acrylate concentrations.

Phaeocystis antarctica forms extensive spring blooms in the Southern Ocean that coincide with high concentrations of dimethylsulfoniopropionate (DMSP), dimethylsulfoxide (DMSO), dimethylsulfide (DMS), and acrylate. We determined how concentrations of these compounds changed during the growth of axenic P. antarctica cultures exposed to light-limiting, sub-saturating, and saturating PAR irradiances. Cellular DMSP concentrations per liter cell volume (CV) ranged between 199 and 403 mmol · LCV -1 , with the highest concentrations observed under light-limiting PAR. Cellular acrylate concentrations did not change appreciably with a change in irradiance level or growth, ranging between 18 and 45 mmol · LCV -1 , constituting an estimated 0.2%-2.8% of cellular carbon. Both dissolved acrylate and DMSO increased substantially with irradiance during exponential growth on a per-cell basis, ranging from 0.91 to 3.15 and 0.24 to 1.39 fmol · cell-1 , respectively, indicating substantial export of these compounds into the dissolved phase. Average cellular DMSO:DMSP ratios increased 7.6-fold between exponential and stationary phases of batch growth, with a 3- to 13-fold increase in cellular DMSO likely formed from abiotic reactions of DMSP and DMS with reactive oxygen species (ROS). At mM levels, cellular DMSP and acrylate are proposed to serve as de facto antioxidants in P. antarctica not regulated by oxidative stress or changes in ROS. Instead, cellular DMSP concentrations are likely controlled by other physiological processes including an overflow mechanism to remove excess carbon via acrylate, DMS, and DMSO during times of unbalanced growth brought on by physical stress or nutrient limitation. Together, these compounds should aid P. antarctica in adapting to a range of PAR irradiances by maintaining cellular functions and reducing oxidative stress.