scholarly journals Global reduction of in situ CO 2 transfer velocity by natural surfactants in the sea-surface microlayer

2020 ◽  
Vol 476 (2234) ◽  
pp. 20190763 ◽  
Author(s):  
Nur Ili Hamizah Mustaffa ◽  
Mariana Ribas-Ribas ◽  
Hanne M. Banko-Kubis ◽  
Oliver Wurl
Keyword(s):  
Western Pacific ◽  
Sea Surface ◽  
Surface Phenomenon ◽  
Gas Transfer ◽  
Surface Microlayer ◽  
Transfer Velocity ◽  
Natural Surfactant ◽  
Sea Surface Microlayer ◽  
The Western Pacific

For decades, the effect of surfactants in the sea-surface microlayer (SML) on gas transfer velocity ( k ) has been recognized; however, it has not been quantified under natural conditions due to missing coherent data on in situ k of carbon dioxide (CO 2 ) and characterization of the SML. Moreover, a sea-surface phenomenon of wave-dampening, known as slicks, has been observed frequently in the ocean and potentially reduces the transfer of climate-relevant gases between the ocean and atmosphere. Therefore, this study aims to quantify the effect of natural surfactant and slicks on the in situ k of CO 2 . A catamaran, Sea Surface Scanner (S 3 ), was deployed to sample the SML and corresponding underlying water, and a drifting buoy with a floating chamber was deployed to measure the in situ k of CO 2 . We found a significant 23% reduction of k above surfactant concentrations of 200 µg Teq l −1 , which were common in the SML except for the Western Pacific. We conclude that an error of approximately 20% in CO 2 fluxes for the Western Pacific is induced by applying wind-based parametrization not developed in low surfactant regimes. Furthermore, we observed an additional 62% reduction in natural slicks, reducing global CO 2 fluxes by 19% considering known frequency of slick coverage. From our observation, we identified surfactant concentrations with two different end-members which lead to an error in global CO 2 flux estimation if ignored.

scholarly journals Assessing the potential for DMS enrichment at the sea-surface and its influence on air–sea flux

2016 ◽  
Author(s):  
C. F. Walker ◽  
M. J. Harvey ◽  
M. J. Smith ◽  
T. G. Bell ◽  
E. S. Saltzman ◽  
...  
Keyword(s):  
Sea Surface ◽  
Gas Transfer ◽  
Surface Microlayer ◽  
Surface Seawater ◽  
Biological Factors ◽  
Near Surface ◽  
Wind Speeds ◽  
Factors Influencing ◽  
Sea Surface Microlayer ◽  
High Enrichment

Abstract. The flux of dimethylsulfide (DMS) to the atmosphere is generally inferred using water sampled at or below 2 m depth, thereby excluding any concentration anomalies at the air–sea interface. Two independent techniques were used to assess the potential for near-surface DMS enrichment to influence DMS emissions and also identify the factors influencing enrichment. DMS measurements in productive frontal waters over the Chatham Rise, east of New Zealand, did not identify any significant DMS gradients between 0.01 and 6 m in sub-surface seawater, whereas DMS enrichment in the sea-surface microlayer was variable, with a mean enrichment factor (EF; the concentration ratio between DMS in the SSM and in sub-surface water) of 1.7. Physical and biological factors influenced sea-surface microlayer DMS concentration, with high enrichment (EF > 1.3) only recorded in a dinoflagellate-dominated bloom, and associated with low to medium wind speeds and near-surface temperature gradients. On occasion, high DMS enrichment preceded periods when the air–sea DMS flux, measured by eddy covariance, exceeded the flux calculated using COARE parameterised gas transfer velocities and measured sub-surface seawater DMS concentrations. The results of these two independent approaches suggest that air–sea emissions may be influenced by near-surface DMS production under certain conditions, and highlights the need for further study to constrain the magnitude and mechanisms of DMS production in the sea surface microlayer.

scholarly journals Assessing the potential for dimethylsulfide enrichment at the sea surface and its influence on air–sea flux

Ocean Science ◽  
2016 ◽  
Vol 12 (5) ◽  
pp. 1033-1048 ◽  
Author(s):  
Carolyn F. Walker ◽  
Mike J. Harvey ◽  
Murray J. Smith ◽  
Thomas G. Bell ◽  
Eric S. Saltzman ◽  
...  
Keyword(s):  
Sea Surface ◽  
Gas Transfer ◽  
Surface Microlayer ◽  
Surface Seawater ◽  
Biological Factors ◽  
Near Surface ◽  
Wind Speeds ◽  
Factors Influencing ◽  
Sea Surface Microlayer ◽  
High Enrichment

Abstract. The flux of dimethylsulfide (DMS) to the atmosphere is generally inferred using water sampled at or below 2 m depth, thereby excluding any concentration anomalies at the air–sea interface. Two independent techniques were used to assess the potential for near-surface DMS enrichment to influence DMS emissions and also identify the factors influencing enrichment. DMS measurements in productive frontal waters over the Chatham Rise, east of New Zealand, did not identify any significant gradients between 0.01 and 6 m in sub-surface seawater, whereas DMS enrichment in the sea-surface microlayer was variable, with a mean enrichment factor (EF; the concentration ratio between DMS in the sea-surface microlayer and in sub-surface water) of 1.7. Physical and biological factors influenced sea-surface microlayer DMS concentration, with high enrichment (EF > 1.3) only recorded in a dinoflagellate-dominated bloom, and associated with low to medium wind speeds and near-surface temperature gradients. On occasion, high DMS enrichment preceded periods when the air–sea DMS flux, measured by eddy covariance, exceeded the flux calculated using National Oceanic and Atmospheric Administration (NOAA) Coupled-Ocean Atmospheric Response Experiment (COARE) parameterized gas transfer velocities and measured sub-surface seawater DMS concentrations. The results of these two independent approaches suggest that air–sea emissions may be influenced by near-surface DMS production under certain conditions, and highlight the need for further study to constrain the magnitude and mechanisms of DMS production in the sea-surface microlayer.

Response : CLOD Spreading in the Sea-Surface Microlayer

Science ◽  
1995 ◽  
Vol 270 (5238) ◽  
pp. 897-898
Author(s):  
Mark M. Littler ◽  
Diane S. Littler
Keyword(s):  
Sea Surface ◽  
Surface Microlayer ◽  
Sea Surface Microlayer

CLOD Spreading in the Sea-Surface Microlayer

Science ◽  
1995 ◽  
Vol 270 (5238) ◽  
pp. 897-897
Author(s):  
M. S. Hale ◽  
J. G. Mitchell
Keyword(s):  
Sea Surface ◽  
Surface Microlayer ◽  
Sea Surface Microlayer

scholarly journals New insights into aerosol and climate in the Arctic

2018 ◽  
Author(s):  
Jonathan P. D. Abbatt ◽  
W. Richard Leaitch ◽  
Amir A. Aliabadi ◽  
Alan K. Bertram ◽  
Jean-Pierre Blanchet ◽  
...  
Keyword(s):  
Long Range ◽  
Mineral Dust ◽  
Sea Surface ◽  
The Arctic ◽  
Long Range Transport ◽  
Surface Microlayer ◽  
Biogeochemical Models ◽  
Sea Surface Microlayer ◽  
Range Transport ◽  
Warming World

Abstract. Motivated by the need to predict how the Arctic atmosphere will change in a warming world, this article summarizes recent advances made by the research consortium NETCARE (Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments) that contribute to our fundamental understanding of Arctic aerosol particles as they relate to climate forcing. The overall goal of NETCARE research has been to use an interdisciplinary approach encompassing extensive field observations and a range of chemical transport, earth system, and biogeochemical models. Several major findings and advances have emerged from NETCARE since its formation in 2013 . (1) Unexpectedly high summertime dimethyl sulfide (DMS) levels were identified in ocean water and the overlying atmosphere in the Canadian Arctic Archipelago (CAA). Furthermore, melt ponds, which are widely prevalent, were identified as an important DMS source. (2) Evidence was found of widespread particle nucleation and growth in the marine boundary layer in the CAA in the summertime. DMS-oxidation-driven nucleation is facilitated by the presence of atmospheric ammonia arising from sea bird colony emissions, and potentially also from coastal regions, tundra, and biomass burning. Via accumulation of secondary organic material (SOA), a significant fraction of the new particles grow to sizes that are active in cloud droplet formation. Although the gaseous precursors to Arctic marine SOA remain poorly defined, the measured levels of common continental SOA precursors (isoprene and monoterpenes) were low, whereas elevated mixing ratios of oxygenated volatile organic compounds were inferred to arise via processes involving the sea surface microlayer. (3) The variability in the vertical distribution of black carbon (BC) under both springtime Arctic haze and more pristine summertime aerosol conditions was observed. Measured particle size distributions and mixing states were used to constrain, for the first time, calculations of aerosol–climate interactions under Arctic conditions. Aircraft- and ground-based measurements were used to better establish the BC source regions that supply the Arctic via long-range transport mechanisms. (4) Measurements of ice nucleating particles (INPs) in the Arctic indicate that a major source of these particles is mineral dust, likely derived from local sources in the summer and long-range transport in the spring. In addition, INPs are abundant in the sea surface microlayer in the Arctic, and possibly play a role in ice nucleation in the atmosphere when mineral dust concentrations are low. (5) Amongst multiple aerosol components, BC was observed to have the smallest effective deposition velocities to high Arctic snow.

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