Evaluation of ocean dimethylsulfide concentration and emission in CMIP6 models

Bock, Josué; Michou, Martine; Nabat, Pierre; Abe, Manabu; Mulcahy, Jane; Olivié, Dirk; Schwinger, Jörg; Suntharalingam, P.; Tjiputra, Jerry; Hulten, Marco van; Watanabe, Michio; Yool, Andrew; Séférian, Roland

doi:10.5194/bg-18-3823-2021

Cited by 31 publications

(38 citation statements)

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“…The work shows that the variability lengthscale for DMS is typically small (< 30 km) and that a substantial proportion of the campaign average variance can be explained by the VLS of key biological (Chl) and physical (density, SSHA) observations (Model 7, Table 1). The results improve confidence in the validity of the biological and physical parameters used to currently parameterise seawater DMS at large scales and used in many global climate models (e.g., Bock et al, 2021;Galí et al, 2018;Mulcahy et al, 2020;Simó & Dachs, 2002). However, there is substantial variability in VLSDMS when assessing individual transects, which suggests that unaccounted-for variables are also important (e.g., light, wind speed, microbial activity).…”

Section: Discussionmentioning

confidence: 59%

Global analysis of the controls on seawater dimethylsulfide spatial variability

Manville

Bell²,

Mulcahy³

et al. 2023

Preprint

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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.

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Section: Discussionmentioning

confidence: 59%

Global analysis of the controls on seawater dimethylsulfide spatial variability

Manville

Bell²,

Mulcahy³

et al. 2023

Preprint

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“…Additionally, strong broadscale correlations between DMS concentration and solar radiation have also been reported [31] and between solar radiation and DMS synthesis [32]. Overall, these studies lend support to parts of the CLAW hypothesis, however modeling attempts to assess the direction and magnitude of the DMS-climate feedback [33][34][35] have often led to contradictory results [36][37][38][39][40]. Other regional modeling studies indicate significant meridional variability in future DMS emissions under warming, with the strongest response simulated at high latitudes in both hemispheres [41][42][43][44].…”

Section: Introductionmentioning

confidence: 73%

“…Bock et al [39] examine trends of surface ocean DMS concentration and flux of four Earth system models (ESMs: CNRM-ESM2-1, MIROC-ES2L, NorESM2-LM, and UKESM1-0-LL) over the recent past and into the future, using Coupled Model Intercomparison Project 6 (CMIP6) simulations. The four ESMs disagree on the sign of the trend of the global DMS flux from 1980 onwards, with two models showing an increase and two models a decrease.…”

Section: Modelingmentioning

confidence: 99%

Climate Change Impacts on the Marine Cycling of Biogenic Sulfur: A Review

Jackson

Gabric

2022

Microorganisms

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A key component of the marine sulfur cycle is the climate-active gas dimethylsulfide (DMS), which is synthesized by a range of organisms from phytoplankton to corals, and accounts for up to 80% of global biogenic sulfur emissions. The DMS cycle starts with the intracellular synthesis of the non-gaseous precursor dimethylsulfoniopropionate (DMSP), which is released to the water column by various food web processes such as zooplankton grazing. This dissolved DMSP pool is rapidly turned over by microbially mediated conversion using two known pathways: demethylation (releasing methanethiol) and cleavage (producing DMS). Some of the formed DMS is ventilated to the atmosphere, where it undergoes rapid oxidation and contributes to the formation of sulfate aerosols, with the potential to affect cloud microphysics, and thus the regional climate. The marine phase cycling of DMS is complex, however, as heterotrophs also contribute to the consumption of the newly formed dissolved DMS. Interestingly, due to microbial consumption and other water column sinks such as photolysis, the amount of DMS that enters the atmosphere is currently thought to be a relatively minor fraction of the total amount cycled through the marine food web—less than 10%. These microbial processes are mediated by water column temperature, but the response of marine microbial assemblages to ocean warming is poorly characterized, although bacterial degradation appears to increase with an increase in temperature. This review will focus on the potential impact of climate change on the key microbially mediated processes in the marine cycling of DMS. It is likely that the impact will vary across different biogeographical regions from polar to tropical. For example, in the rapidly warming polar oceans, microbial communities associated with the DMS cycle will likely change dramatically during the 21st century with the decline in sea ice. At lower latitudes, where corals form an important source of DMS (P), shifts in the microbiome composition have been observed during thermal stress with the potential to alter the DMS cycle.

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“…Sea surface DMS distribution and its change under global warming have been simulated by characterizing main processes of DMS cycle and/or using empirical parameterization of influencing factors like Chl a, MLD, radiation and nutrients (Bock et al, 2021;Cameron-Smith et al, 2011;Gabric et al, 2004;Kloster et al, 2007;Six et al, 2013;Vallina et al, 2007b;Wang et al, 2018). However, distinct ocean environments and complexity of DMS (Hoffmann et al, 2016;Novak et al, 2021;Veres et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

Data-driven exploration of the variability, controls and future changes of dimethyl sulfide in the global surface ocean

Zhou

Chen

Wang

et al. 2022

Preprint

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As the largest natural source of sulfur-containing gases into the atmosphere, ocean organism-derived dimethyl sulfide (DMS) has been considered to play a critical role in the Earth's climate system. Yet there are great uncertainties in modeling the spatiotemporal variations of DMS and incomplete knowledge of influencing factors in different oceanic regions. Moreover, little is known about the future change of global DMS, which limits our understanding of the feedback of marine ecosystem to climate change. Here we develop an artificial neural network model and combine data mining approaches to address these issues. Phytoplankton biomass and salinity are currently predominant factors associated with DMS variability in the coastal and Arctic regions, respectively. In the mid-and low-latitude open oceans, nutrients and temperature are also crucial factors in addition to radiation and mixed layer depth, and their relationships with DMS show reversals when passing certain thresholds. Although the global average DMS concentration and emission slightly decline from 2005 to 2100, they may change considerably in specific regions. In contrast to the DMS decreases in the low-latitudes mainly related with phosphate reduction and temperature rise and in the North Atlantic subpolar gyre attributed to salinity decline, warming will cause DMS increase in the Southern Ocean and sea ice loss will dramatically enhance DMS emission in the Arctic. Although the global negative feedback loop between oceanic DMS and climate may not operate, the future spatial redistribution of DMS may lead to the change in cloud cover pattern and significantly affect regional climate.

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Evaluation of ocean dimethylsulfide concentration and emission in CMIP6 models

Cited by 31 publications

References 100 publications

Global analysis of the controls on seawater dimethylsulfide spatial variability

Global analysis of the controls on seawater dimethylsulfide spatial variability

Climate Change Impacts on the Marine Cycling of Biogenic Sulfur: A Review

Data-driven exploration of the variability, controls and future changes of dimethyl sulfide in the global surface ocean

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