Description: The database includes measurements of the trace gases carbonyl sulfide (OCS) and carbon disulfide (CS2) in seawater (in picomol per liter) and the marine boundary layer (parts per trillion, ppt). It consists of individual datasets compiled from published original data, digitalization from publications (pdf documents) and unpublished data. Only shipborne measurements or measurements from time series stations with a dominant marine signal are included. The database contains mainly surface ocean measurements, but few available profiles down to 〉1000 m are included as well. Temporal resolution ranges from 12 minutes to hourly or monthly intervals. The database includes the following metadata (if available): latitude, longitude, depth, time of sampling, meteorological and physical parameters, main reference, method, contributor(s). The database is intended to facilitate model evaluation and the identification of global patterns. Data in excel and txt-files are identical.

Description: Raw data acquired by position sensors on board RV MERIAN during expedition MSM123 were processed to receive a validated master track which can be used as reference of further expedition data. During MSM123 the motion reference unit Kongsberg SeaTex AS MRU-5 combined with Kongsberg SeaTex AS Seapath 320 and the GPS receivers Trimble SPS855 and SAAB R4 were used as navigation sensors. Data were downloaded from DAVIS SHIP data base (https://dship.bsh.de) with a resolution of 1 sec. Processing and evaluation of the data is outlined in the data processing report. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track.

Description: Raw data acquired by position sensors on board RV MERIAN during expedition MSM123 were processed to receive a validated master track which can be used as reference of further expedition data. During MSM123 the motion reference unit Kongsberg SeaTex AS MRU-5 combined with Kongsberg SeaTex AS Seapath 320 and the GPS receivers Trimble SPS855 and SAAB R4 were used as navigation sensors. Data were downloaded from DAVIS SHIP data base (https://dship.bsh.de) with a resolution of 1 sec. Processing and evaluation of the data is outlined in the data processing report. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track.

Description: Oceanic dimethyl sulfide (DMS) is of interest due to its critical influence on atmospheric sulfur compounds in the marine atmosphere and its hypothesized significant role in global climate. High-resolution shipboard underway measurements of surface seawater DMS and the partial pressure of carbon dioxide (pCO2) were conducted in the Atlantic Ocean and Indian Ocean sectors of the Southern Ocean (SO), the southeast Indian Ocean, and the northwest Pacific Ocean from February to April 2014 during the 30th Chinese Antarctic Research Expedition. The SO, particularly in the region south of 58°S, had the highest mean surface seawater DMS concentration of 4.1 ± 8.3 nM (ranged from 0.1 to 73.2 nM) and lowest mean seawater pCO2 level of 337 ± 50 μatm (ranged from 221 to 411 μatm) over the entire cruise. Significant variations of surface seawater DMS and pCO2 in the seasonal ice zone (SIZ) of SO were observed, which are mainly controlled by biological process and sea ice activity. We found a significant negative relationship between DMS and pCO2 in the SO SIZ using 0.1° resolution, [DMS] seawater = -0.160 [pCO2] seawater + 61.3 (r2 = 0.594, n = 924, p 〈 0.001). We anticipate that the relationship may possibly be utilized to reconstruct the surface seawater DMS climatology in the SO SIZ. Further studies are necessary to improve the universality of this approach. Key Points: • The characteristics of surface water DMS and pCO2 distributions from the Southern Ocean to northwest Pacific Ocean are investigated • The correlations between DMS, pCO2, and environmental parameters are analyzed • Anticorrelation between DMS and pCO2 is found in the seasonal ice zone of the Southern Ocean

Description: During the summer monsoon, the western tropical Indian Ocean is predicted to be a hot spot for dimethylsulfide emissions, the major marine sulfur source to the atmosphere, and an important aerosol precursor. Other aerosol relevant fluxes, such as isoprene and sea spray, should also be enhanced, due to the steady strong winds during the monsoon. Marine air masses dominate the area during the summer monsoon, excluding the influence of continentally derived pollutants. During the SO234-2/235 cruise in the western tropical Indian Ocean from July to August 2014, directly measured eddy covariance DMS fluxes confirm that the area is a large source of sulfur to the atmosphere (cruise average 9.1 μmol m−2 d−1). The directly measured fluxes, as well as computed isoprene and sea spray fluxes, were combined with FLEXPART backward and forward trajectories to track the emissions in space and time. The fluxes show a significant positive correlation with aerosol data from the Terra and Suomi-NPP satellites, indicating a local influence of marine emissions on atmospheric aerosol numbers.

Description: Halogen- and sulfur-containing compounds are supersaturated in the surface ocean, which results in their emission to the atmosphere. These compounds can be transported to the stratosphere, where they impact ozone, the background aerosol layer, and climate. In this study we calculate the seasonal and interannual variability of transport from the West Indian Ocean (WIO) surface to the stratosphere for 2000-2016 with the Lagrangian transport model FLEXPART using ERA-Interim meteorological fields. We investigate the transport relevant for very short lived substances (VSLS) with tropospheric lifetimes corresponding to dimethylsulfide (1 day), methyl iodide (CH3I, 3.5 days), bromoform (CHBr3, 17 days), and dibromomethane (CH2Br2, 150 days). The stratospheric source gas injection of VSLS tracers from the WIO shows a distinct annual cycle associated with the Asian monsoon. Over the 16-year time series, a slight increase in source gas injection from the WIO to the stratosphere is found for all VSLS tracers and during all seasons. The interannual variability shows a relationship with sea surface temperatures in the WIO as well as the El Niño-Southern Oscillation. During boreal spring of El Niño, enhanced stratospheric injection of VSLS from the tropical WIO is caused by positive sea surface temperature anomalies and enhanced vertical uplift above the WIO. During boreal fall of La Niña, strong injection is related to enhanced atmospheric upward motion over the East Indian Ocean and a prolonged Indian summer monsoon season. Related physical mechanisms and uncertainties are discussed in this study

Description: We use isoprene and related field measurements from three different ocean data sets together with remotely sensed satellite data to model global marine isoprene emissions. We show that using monthly mean satellite-derived chl a concentrations to parameterize isoprene with a constant chl a normalized isoprene production rate underpredicts the measured oceanic isoprene concentration by a mean factor of 19 ± 12. Improving the model by using phytoplankton functional type dependent production values and by decreasing the bacterial degradation rate of isoprene in the water column results in only a slight underestimation (factor 1.7 ± 1.2). We calculate global isoprene emissions of 0.21 Tg C for 2014 using this improved model, which is twice the value calculated using the original model. Nonetheless, the sea-to-air fluxes have to be at least 1 order of magnitude higher to account for measured atmospheric isoprene mixing ratios. These findings suggest that there is at least one missing oceanic source of isoprene and, possibly, other unknown factors in the ocean or atmosphere influencing the atmospheric values. The discrepancy between calculated fluxes and atmospheric observations must be reconciled in order to fully understand the importance of marine-derived isoprene as a precursor to remote marine boundary layer particle formation.

Description: The ASTRA-OMZ SO243 cruise on board the R/V Sonne took place between the 5th and 22nd October 2015 from Guayaquil, Ecuador to Antofagasta, Chile. Scientists from Germany, the U.S.A, and Norway participated, spanning chemical, biological, and physical oceanography, as well as atmospheric science. The main goal of the cruise was to determine the impact of low oxygen conditions on trace element cycling and distributions, as well as to determine how air-sea exchange of trace elements is influenced by high productivity conditions. The subsequent impact of trace element ocean-atmosphere exchange on atmospheric chemistry and climate will be determined. A summary of the main preliminary results is below: - a strong source of nitrous oxide (N2O) and carbon dioxide (CO2) was detected from surface waters in the Peruvian upwelling, particularly in the near-coastal area between 9°S and 18°S - generally, surface N2O during the SO-243 cruise was lower than previously observed, probably due to the reduced extent of upwelling events because of El Niño conditions - less dimethyl sulphide (DMS) (〈 2nmol L-1) and isoprene (at 20-30 pmol L-1) than on board previous cruises in the coastal upwelling region (8°-12°S) were detected, likely due to suppressed upwelling off of Peru because of the El Niño conditions - a strong source for atmospheric carbonyl sulphide (OCS) was observed, as well as a strong correlation with oxygen. OCS decreased below the detection limit in oxygen depleted zones. - a strong contrast between normal and El Niño conditions were detected for the halocarbon compounds. Both surface and deeper water was characterized by much larger concentrations of bromocarbons than of iodocarbons during ASTRA-OMZ, which stands in contrast to the previous M91 cruise during neutral conditions. - it appears that the direct flux eddy covariance method was successful for sea-to-air flux measurements of N2O (for the first time) - a pronounced atmospheric inversion layer at approximately 1 km altitude was striking, which was accompanied by an accumulation of high relative humidity and moderate to fresh southerly winds below this inversion. Convective activity was limited and very few precipitation events were detected. Tropospheric ozone levels reveal distinct fluctuations within 9.5°S and 16.5°S latitude. - the oxygen distribution measured at about 9°S showed that the upwelling in October 2015 was very weak. Low oxygen water with less than 5 μmol kg-1 was located only below 250 m in October 2015 - higher oxygen distribution in 2015, as well as the changes in water temperature, salinity and density indicate the influence of El Niño. We have already published our first paper related to El Niño during SO243 (Stramma et al. 2016).

Description: The climate active trace-gas carbonyl sulfide (OCS) is the most abundant sulfur gas in the atmosphere. A missing source in its atmospheric budget is currently suggested, resulting from an upward revision of the vegetation sink. Tropical oceanic emissions have been proposed to close the resulting gap in the atmospheric budget. We present a bottom-up approach including (i) new observations of OCS in surface waters of the tropical Atlantic, Pacific and Indian oceans and (ii) a further improved global box model to show that direct OCS emissions are unlikely to account for the missing source. The box model suggests an undersaturation of the surface water with respect to OCS integrated over the entire tropical ocean area and, further, global annual direct emissions of OCS well below that suggested by top-down estimates. In addition, we discuss the potential of indirect emission from CS2 and dimethylsulfide (DMS) to account for the gap in the atmospheric budget. This bottom-up estimate of oceanic emissions has implications for using OCS as a proxy for global terrestrial CO2 uptake, which is currently impeded by the inadequate quantification of atmospheric OCS sources and sinks.