5 research outputs found

    DataSheet_1_Rapid changes in the surface carbonate system under complex mixing schemes across the Bering Sea: a comparative study of a forward voyage in July and a return voyage in September 2018.pdf

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    Regulated by the rapid changes in temperature, mixing, and biological production during warm seasons, the surface carbonate system in the Bering Sea is subject to significant spatial-temporal variability. However, the seasonal evolution of the carbon cycle and its controls are less clear due to the lack of observations. Here, we present the carbonate data collected during a forward voyage in July and a return voyage in September 2018 across the Bering Sea. For both voyages, we show distinct dissolved inorganic carbon versus total alkalinity (DIC-TA) relationships and partial pressure of CO2 (pCO2) distribution patterns in the Southern Basin (54-57°N), the Northern Basin (57-59°N), the Slope (59-61°N), the Shelf (61-64°N), and the Bering Strait (>64°N). In the Southern Basin, the Northern Basin, and the Slope, surface water was a two end-member mixing of Rainwater and Bering Summer Water (BSW) during the forward voyage and a two end-member mixing of North Pacific Surface Water (NPSW) and BSW during the return voyage. As a result, the observed DIC was almost consistent with the conservative mixing line, with a slight DIC addition/removal of -8.6~5.8 µmol kg-1, suggesting low biological production/respiration during both voyages. Seasonally, the higher factions of NPSW featuring low pCO2 during the return voyage dominated the pCO2 drawdown from July to September in the Southern Basin and the Slope. On the Shelf, the surface water was a two end-member mixing of plume water from the Anadyr River and BSW during both voyages, but the decreased DIC consumption via biological production from 59.9 ± 25.8 µmol kg-1 to 34.8 ± 14.0 µmol kg-1 contributed to the pCO2 increase from July to September. In the Bering Strait, the coastal area was characterized by the influence of plume water from the Anadyr River in July and the coastal upwelling in September. The high biological production in plume water made a strong CO2 sink during the forward voyage, while the upwelling of carbon-enriched subsurface water with minor DIC consumption made the coastal ecosystem a strong CO2 source during the return voyage. In different geographical regions, the observed seawater pCO2 was much lower than the overlying atmospheric CO2, resulting in a net CO2 sink with fluxes of -2.1~-14.0 mmol m-2 d-1 and -2.5~-11.6 mmol m-2 d-1, respectively, during the forward and return voyages.</p

    Significant Underestimation of Gaseous Methanesulfonic Acid (MSA) over Southern Ocean

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    Methanesulfonic acid (MSA), derived from the oxidation of dimethylsulfide (DMS), has a significant impact on biogenic sulfur cycle and climate. Gaseous MSA (MSAg) has been often ignored in previous studies due to its quick conversion to particulate MSA (MSAp) and low concentrations. MSAg, MSAp, and nss-SO42– were observed simultaneously for the first time with high-time-resolution (1 h) in the Southern Ocean (SO). The mean MSAg level reached up to 3.3 ± 1.6 pptv, ranging from ∼24.5 pptv in the SO, contributing to 31% ± 3% to the total MSA (MSAT). A reduction of the MSA to nss-SO42– ratios by about 30% was obtained when MSAg was not accounted for in the calculation, indicating that MSAg was very important in the assessment of the biogenic sulfur contributions in the atmosphere. Mass ratios of MSA to nss-SO42– increased first and then decreased with the temperature from −10 to 5 °C, with a maximum value at the temperature of −3 °C. Positive correlations between MSAg to MSAT ratios and temperature were presented, when the temperature was higher than 5 °C. This study highlights the importance of MSAg for understanding the atmospheric DMS oxidation mechanism and extends the knowledge of MSA formation in the marine atmosphere
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