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Carbon disulfide (CS2) is one of the most important precursors for atmospheric carbonyl sulphide (OCS), a climate relevant trace gas that can serve as a proxy to quantify terrestrial gross primary production. Currently, limited understanding of the production and consumption processes of CS2 in seawater preclude quantifying its marine emissions, which pose major uncertainties in the atmospheric budget of both OCS and CS2. Here we present controlled incubation experiments with natural dissolved organic matter (DOM) from three different oceanic locations, with and without UV light treatment. We show for the first time that in addition to its photochemical production, CS2 is also naturally degraded by UV light. CS2 is also produced in the dark: while the mechanism of this light independent production process is currently unknown, we show that dark production rates scale with the amount of organic sulphur present in DOM. Our results help to disentangle production and consumption processes of CS2 in seawater, in order to facilitate the interpretation of field measurements and ultimately enable modelling approaches.

Carbonyl sulfide (COS) is the major long-lived sulfur gas in the troposphere, and an important precursor for stratospheric sulfate aerosols, which increases earth’s albedo. The main sink of COS is the uptake by terrestrial plants, in a similar pathway to CO2. Therefore, COS is used as a promising proxy for CO2 removal by terrestrial plants (gross primary production, GPP), which regulates the earth’s climate. Currently, COS budget estimates have large uncertainties associated with the magnitude of COS sources and sinks. The COS ocean-atmosphere flux is the largest natural source of tropospheric COS, however, its magnitude is at the heart of a scientific debate with estimates ranging between 200 to 800 Ggr S Yr-1 [1-2].Sulfur isotopes measurements (34S/32S; δ34S) are recently used in an isotopic mass-balance to constrain the COS budget, assuming each end-member has a unique isotopic signature [3]. However, in our previous work [3], we estimated the isotopic signature of the ocean-atmosphere COS flux, based on limited samples from the Mediterranean and Red Seas, which may not be representative of the oceans. In the current work, we present measurements of photochemistry experiments and natural samples from the Atlantic Ocean, sampled during dawn, afternoon, and sunset. Atlantic Ocean samples that were taken during dawn (min COS concentrations) show δ34S value of 14±2‰ (n=8, one outlier with δ34S value of 19.2‰ was excluded). However, samples taken during the afternoon (max concentration) show heavier δ34S values of 18±1‰ (n=6). This significant difference in δ34S values between dawn and afternoon (P-value 0.0003) indicates that COS “dark production” is associated with an isotopic fractionation that produces isotopically lighter COS, supporting the hypothesis that COS “dark production” is related to biotic processes. While COS photoproduction is associated with heavier isotopic values, which we assume are closer to the δ34S value of its biogenic source. This assumption is also supported by our photochemistry experiments, which indicate a small isotopic fractionation of COS photoproduction from cysteine (≤1‰). The isotopic signatures we present here will be used to better understand the main processes controlling oceanic COS production, and better constrain the ocean-atmosphere COS flux. [1] Lennartz, Sinikka T., et al. "Marine carbonyl sulfide (OCS) and carbon disulfide (CS2): a compilation of measurements in seawater and the marine boundary layer." Earth system science data 12.1 (2020): 591-609.[2] Berry, Joe, et al. "A coupled model of the global cycles of carbonyl sulfide and CO2: A possible new window on the carbon cycle." Journal of Geophysical Research: Biogeosciences 118.2 (2013): 842-852.[3] Davidson, Chen, Alon Amrani, and Alon Angert. "Tropospheric carbonyl sulfide mass balance based on direct measurements of sulfur isotopes." Proceedings of the National Academy of Sciences 118.6 (2021): e2020060118.

In our project we are employing semantic data management with the Open Source research data management system (RDMS) CaosDB [1] to link empirical data and simulation output from Earth System Models [2]. The combined management of these data structures allows us to perform complex queries and facilitates the integration of data and meta data into data analysis workflows.One particular challenge for analyses of model output is to keep track of all necessary meta data of each simulation during the whole digital workflow. Especially for open science approaches it is of great importance to properly document - in human- and computer-readable form - all the information necessary to completely reproduce obtained results. Furthermore, we want to be able to feed all relevant data from data analysis back into our data management system, so that we are able to perform complex queries also on data sets and parameters stemming from data analysis workflows.A specific aim of this project is to re-analyse existing sets of simulations under different research questions. This endeavour can become very time consuming without proper documentation in an RDMS.We implemented a workflow, combining semantic research data management with CaosDB and Jupyter notebooks, that keeps track of data loaded into an analysis workspace. Procedures are provided that create snapshots of specific states of the analysis. These snapshots can automatically be interpreted by the CaosDB crawler that is able to insert and update records in the system accordingly. The snapshots include links to the input data, parameter information, the source code and results and therefore provide a high-level interface to the full chain of data processing, from empirical and simulated raw data to the results. For example, input parameters of complex Earth System Models can be extracted automatically and related to model performance. In our use case, not only automated analyses are feasible, but also interactive approaches are supported.[1] Fitschen, T.; Schlemmer, A.; Hornung, D.; tom Wörden, H.; Parlitz, U.; Luther, S. CaosDB—Research Data Management for Complex, Changing, and Automated Research Workflows. Data 2019, 4, 83. https://doi.org/10.3390/data4020083 [2] Schlemmer, A., Merder, J., Dittmar, T., Feudel, U., Blasius, B., Luther, S., Parlitz, U., Freund, J., and Lennartz, S. T.: Implementing semantic data management for bridging empirical and simulative approaches in marine biogeochemistry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11766, https://doi.org/10.5194/egusphere-egu22-11766, 2022.

International audience; We present a comparison of atmospheric transport model (ATM) simulations for carbonyl sulfide (COS), within the framework of the atmospheric tracer transport model intercomparison project "TransCom-COS." Seven ATMs participated in the experiment and provided simulations of COS mixing ratios over the years 2010-2018, using state-of-the-art surface fluxes for various components of the COS budget: biospheric sink, oceanic source, sources from fire and industry. The main goal of TransCom-COS is to investigate the impact of the transport uncertainty and emission distribution in simulating the spatio-temporal variability of tropospheric COS mixing ratios. A control case with seasonal surface fluxes of COS was constructed. The results indicate that the COS mixing ratios are underestimated by at least 50 parts per trillion (ppt) in the tropics, pointing to a missing tropical source. In summer, the mixing ratios are overestimated by at least 50 ppt above 40°N, pointing to a likely missing sink in the high northern latitudes. Regarding the latitudinal profile, the model spread is greater than 60 ppt above 40°N in boreal summer. Regarding the seasonal amplitude, the model spread reaches 50 ppt at 6 out of 15 sites, compared to an observed seasonal amplitude of 100 ppt. All models simulated a too late minimum by at least 2-3 months at two high northern-latitude sites, likely owing to errors in the seasonal cycle in the ocean emissions. This study highlighted the shortcomings in the COS global budget that need to be resolved before using COS as a photosynthesis tracer. Plain Language Summary In this study, we evaluate the state-of-the-art fluxes for various components of the carbonyl sulfide (COS) budget: biospheric sink, oceanic source, sources from fire and industry. A control case with seasonal surface fluxes of COS was constructed. Seven atmospheric transport models provided simulations of COS mixing ratios. Then, the simulated mixing ratios were evaluated against atmospheric measurements at several surface sites. Results show that all models fail to capture the observed latitudinal distribution and that the model spread is small compared to the model-observation mismatch. In summer, the overestimated mixing ratios above 40°N point to a likely missing sink in the high northern latitudes. The underestimated mixing ratios in the tropics point to a missing tropical source. This study highlighted the shortcomings in the COS global budget that need to be resolved before using COS as a photosynthesis tracer. REMAUD ET AL.

We present a comparison of atmospheric transport model simulations for carbonyl sulfide (COS), within the framework of the ongoing atmospheric tracer transport model intercomparison project “TransCom”. Seven atmospheric transport models participated in the inter-comparison experiment and provided simulations of COS mixing ratios in the troposphere over a 9-year period (2010–2018), using prescribed state-of-the-art surface fluxes for various components of the atmospheric COS budget: biospheric sink, oceanic source, sources from fire and industry. Since the biosphere is the largest sink of COS, we tested sink estimates produced by two different biosphere models. The main goals of TransCom-COS are (a) to investigate the impact of the transport uncertainty and emission distribution in simulating the spatio-temporal variability of COS mixing ratios in the troposphere, and (b) to assess the sensitivity of simulated tropospheric COS mixing ratios to the seasonal and diurnal variability of the COS biosphere fluxes. To this end, a control case with state-of-the-art seasonal fluxes of COS was constructed. Models were run with the same fluxes and without chemistry to isolate transport differences. Further, two COS flux scenarios were compared: one using a biosphere flux with a monthly time resolution and the other using a biosphere flux with a three-hourly time resolution. In addition, we investigated the sensitivity of the simulated concentrations to different biosphere fluxes and to indirect oceanic emissions through dimethylsulfide (DMS) and carbon disulfide (CS2). The modelled COS mixing ratios were assessed against in-situ observations from surface stations and aircraft.

For the first time, we present a comparison of atmospheric transport models for Carbonyl Sulfide (COS), a promising photosynthesis tracer, within the framework of the ongoing Atmospheric Tracer Transport Model Intercomparison Project (TransCom). Seven atmospheric transport models participated in the inter-comparison experiment and provided simulations of COS mixing ratios in the troposphere over a 10-year period (2010–2019), using prescribed state of the art surface fluxes for each component of the atmospheric COS budget (i.e., linked to vegetation, soil, ocean, fire and industry). The main goals of TransCom-COS are (a) to investigate the roles of the transport uncertainty and emission distribution in simulating the spatio-temporal variability of COS mixing ratio in the troposphere and (b) to assess the sensitivity of simulated tropospheric COS mixing ratio to the seasonal variability of the COS terrestrial fluxes. Models were run with the same prior emissions and without chemistry to isolate differences due to transport. Two COS flux scenarios were compared: one using a biospheric flux with a monthly time resolution and the other one using a biospheric flux with a tri-hourly time resolution. In addition, we investigated the sensitivity of the simulated concentrations to different biospheric fluxes and to indirect oceanic emissions through DMS. The modelled COS mixing ratios were assessed against observations from in situ surface stations, aircraft and ground based FTIR stations. Using the state of the art surface fluxes for each component of the COS budget, preliminary results indicate that all transport models fail to capture the surface latitudinal distribution of COS. The COS mixing ratios are underestimated by at least 50 ppt in the tropics, pointing to a missing tropical source. In summer, the mixing ratios are overestimated by at least 50 ppt above 40N, pointing to a likely missing sink in the high northern latitudes during this period. The surface variability of COS mixing ratios is more sensitive to transport models than to a change in biospheric fluxes (two estimates based on different global Land Surface Models). Regarding the seasonal mean latitudinal profiles, the model spread is greater than 60 ppt above 40N in boreal summer and in the vicinity of anthropogenic sources. Regarding the seasonal amplitude, the model spread reaches 50 ppt at 6 sites out of 15, compared to an observed seasonal amplitude of 100 ppt. All models simulated a too late minimum by 2 to 3 months at northern sites ALT, BRW owing to likely errors in the seasonal cycle in the ocean emissions. Finally, the temporal resolution of the biospheric fluxes (monthly versus tri-hourly) has a small impact (less than 20 ppt) on the mean seasonal cycle at stations from the NOAA network.

The questions that chemical oceanographers prioritize over the coming decades, and the methods we use to address these questions, will define our field's contribution to 21st century science. In recognition of this, the U.S. National Science Foundation and National Oceanic and Atmospheric Administration galvanized a community effort (the Chemical Oceanography MEeting: A BOttom-up Approach to Research Directions, or COME ABOARD) to synthesize bottom-up perspectives on selected areas of research in Chemical Oceanography. Representing only a small subset of the community, COME ABOARD participants did not attempt to identify targeted research directions for the field. Instead, we focused on how best to foster diverse research in Chemical Oceanography, placing emphasis on the following themes: strengthening our core chemical skillset; expanding our tools through collaboration with chemists, engineers, and computer scientists; considering new roles for large programs; enhancing interface research through interdisciplinary collaboration; and expanding ocean literacy by engaging with the public. For each theme, COME ABOARD participants reflected on the present state of Chemical Oceanography, where the community hopes to go and why, and actionable pathways to get there. A unifying concept among the discussions was that dissimilar funding structures and metrics of success may be required to accommodate the various levels of readiness and stages of knowledge development found throughout our community. In addition to the science, participants of the concurrent Dissertations Symposium in Chemical Oceanography (DISCO) XXV, a meeting of recent and forthcoming Ph.D. graduates in Chemical Oceanography, provided perspectives on how our field could show leadership in addressing long-standing diversity and early-career challenges that are pervasive throughout science. Here we summarize the COME ABOARD Meeting discussions, providing a synthesis of reflections and perspectives on the field., National Science Foundation (U.S.) (Grant OCE-1356972), National Science Foundation (U.S.) (Grant OCE-1737724), United States. National Oceanic and Atmospheric Administration (Grant NA16NMF4320058)