Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

Bell, Thomas G.; Bruyn, Warren de; Miller, S. D.; Ward, Brian; Christensen, Kai Håkon; Saltzman, E. S.

doi:10.5194/acpd-13-13285-2013

Cited by 5 publications

(5 citation statements)

References 73 publications

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“…[]. In contrast, DMS is moderately soluble, and recent eddy correlation measurements at high wind speeds do not suggest gas‐transfer velocity enhancements at high‐wind speeds [ Bell et al ., ; Goddijn‐Murphy et al ., ; Marandino et al ., ; Yang et al ., ]. When we recalculate our fluxes using Nightingale et al .…”

Section: Resultsmentioning

confidence: 99%

Exploiting satellite earth observation to quantify current global oceanic DMS flux and its future climate sensitivity

Land

Shutler

Bell

et al. 2014

J. Geophys. Res. Oceans

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We used coincident Envisat RA2 and AATSR temperature and wind speed data from 2008/2009 to calculate the global net sea-air flux of dimethyl sulfide (DMS), which we estimate to be 19.6 Tg S a 21 . Our monthly flux calculations are compared to open ocean eddy correlation measurements of DMS flux from 10 recent cruises, with a root mean square difference of 3.1 lmol m 22 day 21 . In a sensitivity analysis, we varied temperature, salinity, surface wind speed, and aqueous DMS concentration, using fixed global changes as well as CMIP5 model output. The range of DMS flux in future climate scenarios is discussed. The CMIP5 model predicts a reduction in surface wind speed and we estimate that this will decrease the global annual sea-air flux of DMS by 22% over 25 years. Concurrent changes in temperature, salinity, and DMS concentration increase the global flux by much smaller amounts. The net effect of all CMIP5 modelled 25 year predictions was a 19% reduction in global DMS flux. 25 year DMS concentration changes had significant regional effects, some positive (Southern Ocean, North Atlantic, Northwest Pacific) and some negative (isolated regions along the Equator and in the Indian Ocean). Using satellite-detected coverage of coccolithophore blooms, our estimate of their contribution to North Atlantic DMS emissions suggests that the coccolithophores contribute only a small percentage of the North Atlantic annual flux estimate, but may be more important in the summertime and in the northeast Atlantic.

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Section: Resultsmentioning

confidence: 99%

Exploiting satellite earth observation to quantify current global oceanic DMS flux and its future climate sensitivity

Land

Shutler

Bell

et al. 2014

J. Geophys. Res. Oceans

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“…The separation between enhanced gas transfer due to bubbles and wave-induced turbulence at high winds has not been fully established and will be gas specific (Woolf 2005;Asher and Wanninkhof 1998). Field studies with dimethyl sulfide (DMS), which has a solubility of an order of magnitude greater than CO 2 , show significantly lower gas transfer velocities at high winds than CO 2 (Yang et al 2011;Bell et al 2013). This suggests that bubble-mediated processes might have a large impact on gas transfer at high winds and cause large deviations for other gases compared with the relationship for CO 2 shown in Fig.…”

Section: Wanninkhofmentioning

confidence: 99%

Relationship between wind speed and gas exchange over the ocean revisited

Wanninkhof

2014

Limnology & Ocean Methods

1,129

1,127

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The relationship between gas exchange and wind speed is used extensively for estimating bulk fluxes of atmospheric gases across the air-sea interface. Here, I provide an update on the frequently used method of Wanninkhof (1992). The update of the methodology reflects advances that have occurred over the past two decades in quantifying the input parameters. The general principle of obtaining a relationship constrained by the globally integrated bomb-14 CO 2 flux into the ocean remains unchanged. The improved relationship is created using revised global ocean 14 C inventories and improved wind speed products. Empirical relationships of the Schmidt number, which are necessary to determine the fluxes, are extended to 40°C to facilitate their use in the models. The focus is on the gas exchange of carbon dioxide, but the suggested functionality can be extended to other gases at intermediate winds ( -0.5 where k is the gas transfer velocity, is the average squared wind speed, and Sc is the Schmidt number, has a 20% uncertainty. The relationship is in close agreement with recent parameterizations based on results from gas exchange process studies over the ocean.

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“…The effect of bubble-mediated gas transfer is important for less soluble gases but less so for OVOCs, so Nightingale et al [2000] potentially overestimate k w . However, although real, any effect is probably small because the wind speed regime on the AMT19 cruise was low to moderate (average 7.0 m s À1 , range 1.4-13.6 m s À1 ) where bubble effects on gas exchange are less important than at higher wind speeds [e.g., see Bell et al, 2013]. In addition, the high solubility of the OVOCs means that the majority of the resistance to gas exchange is in the air phase [Beale, 2011;Rowe et al, 2011], thus minimizing the importance of any errors in deriving k w from Nightingale et al [2000].…”

Section: Air-sea Transfer Of Ovocs During Amt19mentioning

confidence: 99%

Methanol, acetaldehyde, and acetone in the surface waters of the Atlantic Ocean

Beale

Dixon

Arnold

et al. 2013

J. Geophys. Res. Oceans

126

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[1] Oceanic methanol, acetaldehyde, and acetone concentrations were measured during an Atlantic Meridional Transect (AMT) cruise from the UK to Chile (49 N to 39 S) in 2009. Methanol (48-361 nM) and acetone (2-24 nM) varied over the track with enrichment in the oligotrophic Northern Atlantic Gyre. Acetaldehyde showed less variability (3-9 nM) over the full extent of the transect. These oxygenated volatile organic compounds (OVOCs) were also measured subsurface, with methanol and acetaldehyde mostly showing homogeneity throughout the water column. Acetone displayed a reduction below the mixed layer. OVOC concentrations did not consistently correlate with primary production or chlorophyll-a levels in the surface Atlantic Ocean. However, we did find a novel and significant negative relationship between acetone concentration and bacterial leucine incorporation, suggesting that acetone might be removed by marine bacteria as a source of carbon. Microbial turnover of both acetone and acetaldehyde was confirmed. Modeled atmospheric data are used to estimate the likely air-side OVOC concentrations. The direction and magnitude of air-sea fluxes vary for all three OVOCs depending on location. We present evidence that the ocean may exhibit regions of acetaldehyde under-saturation. Extrapolation suggests that the Atlantic Ocean represents an overall source of these OVOCs to the atmosphere at 3, 3, and 1 Tg yr À1 for methanol, acetaldehyde, and acetone, respectively.

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Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

Cited by 5 publications

References 73 publications

Exploiting satellite earth observation to quantify current global oceanic DMS flux and its future climate sensitivity

Exploiting satellite earth observation to quantify current global oceanic DMS flux and its future climate sensitivity

Relationship between wind speed and gas exchange over the ocean revisited

Methanol, acetaldehyde, and acetone in the surface waters of the Atlantic Ocean

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