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.

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 Formation and distribution of sea-surface microlayers

2010 ◽  
Vol 7 (4) ◽  
pp. 5719-5755 ◽  
Author(s):  
O. Wurl ◽  
E. Wurl ◽  
L. Miller ◽  
K. Johnson ◽  
S. Vagle
Keyword(s):  
Wind Speed ◽  
Primary Production ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Average Wind ◽  
The Pacific ◽  
Sea Surface Microlayer ◽  
Natural Surfactants

Abstract. Results from a study of surfactants in the sea-surface microlayer (SML) in different regions of the ocean (subtropical, temperate, polar) suggest that this interfacial layer between the ocean and atmosphere covers the ocean's surface to a significant extent. Threshold values at which primary production acts as a significant source of natural surfactants have been derived from the enrichment of surfactants in the SML relative to underlying water and local primary production. Similarly, we have also derived a wind speed threshold at which the SML is disrupted. The results suggest that surfactant enrichment in the SML is typically greater in oligotrophic regions of the ocean than in more productive waters. Furthermore, the enrichment of surfactants persisted at wind speeds of up to 10 m s−1 without any observed depletion above 5 m s−1. This suggests that the SML is stable enough to exist even at the global average wind speed of 6.6 m s−1. Global maps of primary production and wind speed are used to estimate the ocean's SML coverage. The maps indicate that wide regions of the Pacific and Atlantic Oceans between 30° N and 30° S are more significantly affected by the SML than northern of 30° N and southern of 30° S due to higher productivity (spring/summer blooms) and wind speeds exceeding 12 m s−1 respectively.

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 Effect of wind speed on the size distribution of biogenic gel particles in the sea surface microlayer: Insights from a wind wave channel experiment

2017 ◽  
Author(s):  
Cui-Ci Sun ◽  
Martin Sperling ◽  
Anja Engel
Keyword(s):  
Wind Speed ◽  
Size Distribution ◽  
Wind Wave ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Wind Speeds ◽  
Wave Channel ◽  
Gel Particles ◽  
Sea Surface Microlayer ◽  
Physical And Chemical

Abstract. Biogenic gels particles, such as transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP), are important components in the sea-surface microlayer (SML). The accumulation of gel particles in the SML and their potential implications for gas exchange and emission of primary organic aerosols have generated considerable research interest in recent years. Changes in the particle-size distribution (PSD) can provide important information for the understanding of physical and chemical processes involving gel particles, such as aggregation, degradation or loss. So far, little is known regarding the influence of wind speed on the size distribution of marine gel particles in the surface microlayer. Here, we present results on the effect of different wind speeds on the PSD of TEP and CSP during a wind wave channel experiment in the Aeolotron. Total area of TEP and CSP were exponentially related to wind speed in the SML. At wind speeds  8 m s−1 also significantly altered the PSD slope of TEP in the 2–16 μm size range toward smaller size. Changes in spectral slopes at wind speeds > 8 m s−1 were more pronounced for TEP than for CSP indicating a high aggregation potential for TEP in the SML, potentially enhancing the export of TEP by aggregates settling out of the SML. Our experiment provided evidence for the control of wind speed on the accumulation of biogenic gel particles and their PSD changes, providing a useful insight into particle dynamics and biophysical processes at the interface between air and sea.

scholarly journals Formation and global distribution of sea-surface microlayers

2011 ◽  
Vol 8 (1) ◽  
pp. 121-135 ◽  
Author(s):  
O. Wurl ◽  
E. Wurl ◽  
L. Miller ◽  
K. Johnson ◽  
S. Vagle
Keyword(s):  
Wind Speed ◽  
Primary Production ◽  
Trophic Levels ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
The Pacific ◽  
Sea Surface Microlayer ◽  
Natural Surfactants

Abstract. Results from a study of surfactants in the sea-surface microlayer (SML) in different regions of the ocean (subtropical, temperate, polar) suggest that this interfacial layer between the ocean and atmosphere covers the ocean's surface to a significant extent. New, experimentally-derived threshold values at which primary production acts as a significant source of natural surfactants to the microlayer are coupled with a wind speed threshold at which the SML is presumed to be disrupted, and the results suggest that surfactant enrichment in the SML is greater in oligotrophic regions of the ocean than in more productive waters. Furthermore, surfactant enrichments persisted at wind speeds of up to 10 m s−1, without any observed depletion above 5 m s−1. This suggests that the SML is stable enough to exist even at the global average wind speed of 6.6 m s−1. Using our observations of the surfactant enrichments at various trophic levels and wind states, global maps of primary production and wind speed allow us to extrapolate the ocean's SML coverage . The maps indicate that wide regions of the Pacific and Atlantic Oceans between 30° N and 30° S may be more significantly covered with SML than north of 30° N and south of 30° S, where higher productivity (spring/summer blooms) and wind speeds exceeding 12 m s−1 may prevent extensive SML formation.

scholarly journals Effect of wind speed on the size distribution of gel particles in the sea surface microlayer: insights from a wind–wave channel experiment

2018 ◽  
Vol 15 (11) ◽  
pp. 3577-3589 ◽  
Author(s):  
Cui-Ci Sun ◽  
Martin Sperling ◽  
Anja Engel
Keyword(s):  
Wind Speed ◽  
Size Distribution ◽  
Wind Wave ◽  
Sea Surface ◽  
Surface Microlayer ◽  
Wind Speeds ◽  
Wave Channel ◽  
Gel Particles ◽  
Sea Surface Microlayer ◽  
Low Wind Speeds

Abstract. Gel particles, such as transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP), are important organic components in the sea surface microlayer (SML). Here, we present results on the effect of different wind speeds on the accumulation and size distribution of TEP and CSP during a wind wave channel experiment in the Aeolotron. Total areas of TEP (TEPSML) and CSP (CSPSML) in the surface microlayer were exponentially related to wind speed. At wind speeds < 6 m s−1, accumulation of TEPSML and CSPSML occurred, decreasing at wind speeds of > 8 m s−1. Wind speeds > 8 m s−1 also significantly altered the size distribution of TEPSML in the 2–16 µm size range towards smaller sizes. The response of the CSPSML size distribution to wind speed varied through time depending on the biogenic source of gels. Wind speeds > 8 m s−1 decreased the slope of CSPSML size distribution significantly in the absence of autotrophic growth. For the slopes of TEP and CSP size distribution in the bulk water, no significant difference was observed between high and low wind speeds. Changes in spectral slopes between high and low wind speed were higher for TEPSML than for CSPSML, indicating that the impact of wind speed on size distribution of gel particles in the SML may be more pronounced for TEP than for CSP, and that CSPSML are less prone to aggregation during the low wind speeds. Addition of an E. huxleyi culture resulted in a higher contribution of submicron gels (0.4–1 µm) in the SML at higher wind speed (> 6 m s−1), indicating that phytoplankton growth may potentially support the emission of submicron gels with sea spray aerosol.

scholarly journals High wind speeds prevent formation of a distinct bacterioneuston community in the sea-surface microlayer

2017 ◽  
Vol 93 (5) ◽  
Author(s):  
Janina Rahlff ◽  
Christian Stolle ◽  
Helge-Ansgar Giebel ◽  
Thorsten Brinkhoff ◽  
Mariana Ribas-Ribas ◽  
...  
Keyword(s):  
Sea Surface ◽  
Surface Microlayer ◽  
High Wind ◽  
Wind Speeds ◽  
Sea Surface Microlayer

scholarly journals The Determination of Surfactants at the Sea Surface

2019 ◽  
Author(s):  
Leon King ◽  
Ieuan J. Roberts ◽  
Liselotte Tinel ◽  
Lucy J. Carpenter
Keyword(s):  
Surface Film ◽  
Ocean Basin ◽  
Sea Surface ◽  
Ionic Surfactant ◽  
Surface Microlayer ◽  
High Wind ◽  
Film Pressure ◽  
Wind Speeds ◽  
Sea Surface Microlayer ◽  
Basin Scale

Abstract. The surface of the ocean is a critical yet little understood interface that covers more than 70 % of the Earth's surface. Evidence is emerging that the so-called sea surface microlayer (SML) – the thin film of the ocean surface which is enriched in surface active material and contains large chemical, physical and biological gradients that separate it from the underlying seawater – plays an important role in regulating the air-sea exchange of gases and aerosols. Indeed, recent studies have suggested that (a) there is a ubiquitous enrichment of surfactants in the SML even at high wind speeds; (b) surfactants exert a control on air-sea CO2 exchange at the ocean basin scale, even at high wind, high latitude oceans, and (c) interfacial photochemistry within the SML serves as a major global abiotic source of volatile organic compounds (VOCs), competitive with emissions from marine biology. These conclusions are based on measurements of surfactant activity (SA) from alternating current (AC) voltammetry, showing enrichment of SA in the SML compared to subsurface waters at the ocean basin scale even at high wind speeds, and a relationship between SA and suppression of air-sea gas exchange. SA is calibrated using the large non-ionic surfactant Triton X-100 (TX-100) and expressed in concentration units of TX-100 equivalents. Here, we show that the response of SA-voltammetry varies widely for different surfactants, depending on the surfactant's molecular weight and its charge. Further, even at short deposition times of 15 s, the response becomes saturated above total surfactant concentrations of 1–2 mg L-1, which are at the high end of those observed in the SML. This behaviour was also observed when comparing measurements of seawater and lake water by SA voltammetry to surface film pressure (Δγ) measured by tensiometry. These two different methods for assessing the presence of surfactants showed that, while SA generally increases as surface film pressure increases, the correlation is poor and SA values plateau above ∼2 mg L-1 TX-100 eq. The implications of these results are that SA might not accurately capture variations in soluble and insoluble surfactants present in ocean waters.

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