Description: During two cruises wiht RV Sonne, SO234-2 from 8 to 19 July 2014 (Durban, South Africa to Port Louis, Mauritius) and SO235 from 23 July to 7 August 2014 (Port Louis, Mauritius to Malé, Maldives), within the SPACES (Science Partnerships for the Assessment of Complex Earth System Processes) and OASIS (Organic very short-lived Substances and their air sea exchange from the Indian Ocean to the Stratosphere) research projects, surface water samples were sampled from a continuous running pump in the hydrographic shaft of RV Sonne at a depth of 5 m. Deep water samples were taken from a Niskin-bottle rosette sampler. The samples were then analyzed for halogenated compounds using a purge and trap system onboard, which was attached to a gas chromatograph with an electron capture detector for surface water samples and a GC/MS Agilent 5975 for the deep water samples. An analytical reproducibility of 10% was determined from measuring duplicate water samples, detection limit was 0.2 pmol /L. Calibration was performed with several dilutions of a mixed-compound standard prepared in methanol.

Description: Halocarbons, halogenated short-chained hydrocarbons, are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling obtained during the M91 cruise onboard the research vessel Meteor in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3) and dibromomethane (CH2Br2) correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group as likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I) of up to 35.4 pmol L-1, chloroiodomethane (CH2ClI) of up to 58.1 pmol L-1 and diiodomethane (CH2I2) of up to 32.4 pmol L-1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM) components measured in the surface water. Our results suggest a biological source of these compounds as significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt), CH2ClI (up to 2.5 ppt) and CH2I2 (3.3 ppt) above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. The enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels.

Description: Halocarbons from oceanic sources contribute to halogens in the troposphere, and can be transported into the stratosphere where they take part in ozone depletion. This paper presents distribution and sources in the equatorial Atlantic from June and July 2011 of the four compounds bromoform (CHBr3), dibromomethane (CH2Br2), methyl iodide (CH3I) and diiodomethane (CH2I2). Enhanced biological production during the Atlantic Cold Tongue (ACT) season, indicated by phytoplankton pigment concentrations, led to elevated concentrations of CHBr3 of up to 44.7 and up to 9.2 pmol/L for CH2Br2 in surface water, which is comparable to other tropical upwelling systems. While both compounds correlated very well with each other in the surface water, CH2Br2 was often more elevated in greater depth than CHBr3, which showed maxima in the vicinity of the deep chlorophyll maximum. The deeper maximum of CH2Br2 indicates an additional source in comparison to CHBr3 or a slower degradation of CH2Br2. Concentrations of CH3I of up to 12.8 pmol/L in the surface water were measured. In contrary to expectations of a predominantly photochemical source in the tropical ocean, its distribution was mostly in agreement with biological parameters, indicating a biological source. CH2I2 was very low in the near surface water with maximum concentrations of only 3.7 pmol/L. CH2I2 showed distinct maxima in deeper waters similar to CH2Br2. For the first time, diapycnal fluxes of the four halocarbons from the upper thermocline into and out of the mixed layer were determined. These fluxes were low in comparison to the halocarbon sea-to-air fluxes. This indicates that despite the observed maximum concentrations at depth, production in the surface mixed layer is the main oceanic source for all four compounds and one of the main driving factors of their emissions into the atmosphere in the ACT-region. The calculated production rates of the compounds in the mixed layer are 34 ± 65 pmol/m**3/h for CHBr3, 10 ± 12 pmol/m**3/h for CH2Br2, 21 ± 24 pmol/m**3/h for CH3I and 384 ± 318 pmol/m**3/h for CH2I2 determined from 13 depth profiles.

Description: In order to investigate production pathways of methyl iodide and controls on emissions from the surface ocean, a set of repeated in-vitro incubation experiments were performed over an annual cycle in the context of a time-series of in-situ measurements in Kiel Fjord (54.3 N, 10.1E). The incubation experiments revealed a diurnal variation of methyl iodide in samples exposed to natural light, with maxima during day time and losses during night hours. The amplitude of the daily accumulation varied seasonally and was not affected by filtration (0.2µm), consistent with a photochemical pathway for CH3I production. The methyl iodide loss rate during night time correlated with the concentration accumulated during daytime. Daily (24 hour) net production (Pnet) was similar in magnitude between in vitro and in situ mass balances. However, the estimated gross production (Pgross) of methyl iodide ranged from -0.07 to 2.24 pmol/day and were 5 times higher in summer than Pnet calculated from the in-situ study [Shi et al., 2014]. The large excess of Pgross over Pnet revealed by the in-vitro (incubation) experiments in summer is a consequence of large losses of CH3I by as-yet uncharacterized processes (e.g. biological degradation or chemical pathways other than Cl- substitution).

Description: Oceanic very short-lived substances (VSLSs), such as bromoform (CHBr3), contribute to stratospheric halogen loading and, thus, to ozone depletion. However, the amount, timing, and region of bromine delivery to the stratosphere through one of the main entrance gates, the Indian summer monsoon circulation, are still uncertain. In this study, we created two bromoform emission inventories with monthly resolution for the tropical Indian Ocean and west Pacific based on new in situ bromoform measurements and novel ocean biogeochemistry modeling. The mass transport and atmospheric mixing ratios of bromoform were modeled for the year 2014 with the particle dispersion model FLEXPART driven by ERA-Interim reanalysis. We compare results between two emission scenarios: (1) monthly averaged and (2) annually averaged emissions. Both simulations reproduce the atmospheric distribution of bromoform from ship- and aircraft-based observations in the boundary layer and upper troposphere above the Indian Ocean reasonably well.

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: Upper-ocean velocities along the cruise track of RV SONNE cruise SO287 were continuously collected by a vessel-mounted Teledyne RD Instruments 75 kHz Ocean Surveyor ADCP. The transducer was located at 6.0 m below the water line. The instrument was operated in narrowband mode with 8 m bins and a blanking distance of 8 m, while 100 bins were recorded using a pulse of 1.45 s. The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS). Heading, pitch and roll data from the ship's gyro platforms and the navigation data were used by the data acquisition software VmDas internally to convert ADCP velocities into earth coordinates. Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline. Data post-processing included water track calibration of the misalignment angle (-0.13° +/- 0.5240°) and scale factor (0.9994 +/- 0.0077) of the Ocean Surveyor signal. The average interval was set to 60 s.

Description: The atmospheric CO₂ and CH4 concentrations were monitored throughout the cruise using a cavity ring down spectrometer (CRDS, Picarro G2301-f) and GEOMARs 'Atmospheric Intake System' (AIS).