Description: The potential impacts of seawater acidification on the concentrations of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), dissolved acrylic acid (AAd) and various volatile halocarbons, including CH3Cl, CHBr3, CH2Br2, CHBr2Cl, CHBrCl2 and CH3I, were examined during a laboratory CO2 perturbation experiment for the microalgae Phaeocystis globosa and Nitzschia closterium. The microalgae were exposed to ambient CO2 conditions (390–540 µatm; 1 µatm = 0.1 Pa) and to projected concentrations for the end of the century (760–1000 µatm, high carbon (HC)). The growth rate of the two species remained unaffected by elevated CO2. Results showed a 48 and 37 % decline in the DMS concentration normalised to cell density in P. globosa and N. closterium cultures in the HC treatment compared with the ambient treatment. No significant difference was observed for DMSPp and DMSPd in the two microalgae cultures between the two CO2 levels. The mean AAd concentrations in the P. globosa culture showed a 28 % decline in the HC treatment. By contrast, the cell-normalised concentrations of AAd in the HC treatment were 45 % lower than in the ambient treatment in N. closterium cultures. No CO2-induced effects were observed for CH3Cl, CHBr3, CHBr2Cl, CHBrCl2 and CH3I, but cell-normalised concentrations of CH2Br2 in N. closterium cultures showed a 32 % decline in the HC treatment relative to the ambient level. These results show that the metabolism processes responsible for the production of climate-active gases in phytoplankton may be affected by high CO2 levels. There may be a potential delay in the responses of trace gas emissions to elevated pCO2.

Description: Decreasing sea ice and increasing marine navigability in northern latitudes have changed Arctic ship traffic patterns in recent years and are predicted to increase annual ship traffic in the Arctic in the future. Development of effective regulations to manage environmental impacts of shipping requires an understanding of ship emissions and atmospheric processing in the Arctic environment. As part of the summer 2014 NETCARE (Network on Climate and Aerosols) campaign, the plume dispersion and gas and particle emission factors of effluents originating from the Canadian Coast Guard icebreaker Amundsen operating near Resolute Bay, NU, Canada, were investigated. The Amundsen burned distillate fuel with 1.5 wt% sulfur. Emissions were studied via plume intercepts using the Polar 6 aircraft measurements, an analytical plume dispersion model, and using the FLEXPART-WRF Lagrangian particle dispersion model. The first plume intercept by the research aircraft was carried out on 19 July 2014 during the operation of the Amundsen in the open water. The second and third plume intercepts were carried out on 20 and 21 July 2014 when the Amundsen had reached the ice edge and operated under ice-breaking conditions. Typical of Arctic marine navigation, the engine load was low compared to cruising conditions for all of the plume intercepts. The measured species included mixing ratios of CO2, NOx, CO, SO2, particle number concentration (CN), refractory black carbon (rBC), and cloud condensation nuclei (CCN). The results were compared to similar experimental studies in mid-latitudes. Plume expansion rates were calculated using the analytical model and found to be D0.75+0.81, 0.93+0.37, and 1.19+0.39 for plumes 1, 2, and 3, respectively. These rates were smaller than prior studies conducted at mid-latitudes, likely due to polar boundary layer dynamics, including reduced turbulent mixing compared to mid- latitudes. All emission factors were in agreement with prior observations at low engine loads in mid-latitudes. Ice-breaking increased the NOx emission factor from EFNOx 43.1+15.2 to 71.6+9.68 and 71.4+4.14 g kg-diesel-1 for plumes 1, 2, and 3, likely due to changes in combustion temperatures. The CO emission factor was EFCO 137+120, 12.5+3.70 and 8.13+1.34 g kg-diesel-1 for plumes 1, 2, and 3. The rBC emission factor was EFrBC D0.202+0.052 and 0.202+0.125 g kg-diesel-1 for plumes 1 and 2. The CN emission factor was reduced while ice-breaking from EFCN 2.41+0.47 to 0.45+0.082 and 0.507+0.037+1016 kg-diesel+1 for plumes 1, 2, and 3. At 0.6% supersaturation, the CCN emission factor was comparable to observations in mid-latitudes at low engine loads with EFCCN D3.03+0.933, 1.39+0.319, and 0.650+0.136+1014 kg-diesel-1 for plumes 1, 2, and 3.

Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 15 (2018): 2449–2465, doi:10.5194/bg-15-2449-2018.

Description: We present seawater concentrations of dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP) measured across a transect from the Labrador Sea to the Canadian Arctic Archipelago during summer 2015. Using an automated ship-board gas chromatography system and a membrane-inlet mass spectrometer, we measured a wide range of DMS (∼ 1 to 18 nM) and DMSP (∼ 1 to 150 nM) concentrations. The highest DMS and DMSP concentrations occurred in a localized region of Baffin Bay, where surface waters were characterized by high chlorophyll a (chl a) fluorescence, indicative of elevated phytoplankton biomass. Across the full sampling transect, there were only weak relationships between DMS(P), chl a fluorescence and other measured variables, including positive relationships between DMSP : chl a ratios and several taxonomic marker pigments, and elevated DMS(P) concentrations in partially ice-covered areas. Our high spatial resolution measurements allowed us to examine DMS variability over small scales (〈 1 km), documenting strong DMS concentration gradients across surface hydrographic frontal features. Our new observations fill in an important observational gap in the Arctic Ocean and provide additional information on sea–air DMS fluxes from this ocean region. In addition, this study constitutes a significant contribution to the existing Arctic DMS(P) dataset and provides a baseline for future measurements in the region.

Description: This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) through the Climate Change and Atmospheric Research program (Arctic-GEOTRACES).