Bubbles and the air-sea exchange of gases in near-saturation conditions

Woolf, David; Thorpe, S. A.

doi:10.1357/002224091784995765

Cited by 251 publications

(283 citation statements)

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“…Models of bubble-mediated gas transfer suggest that if the bubble gas flux is a significant fraction.of the net gas flux, k&) measured at a particular Bc will be larger than kLe(C) measured for the same gas at the same B, (Memery and Merlivat, 1985;Woolf and Thorpe, 1992). Furthermore, this invasion-evasion asymmetry will be a function of a with the asymmetry increasing as a decreases.…”

Section: Distribution Of This Document Is Unlimited --mentioning

confidence: 96%

“…Bubble-mediated gas transfer models indicate that the gas flux due to bubbles decreases as a increases (Memery and Merlivat 1985;Woolf and Thorpe, 1992), suggesting that bubble plumes generated by breaking waves will be of little importance in the air-sea exchange of CO,. However, the WST measurements show that the simulated breaking waws are very effective at increasing both kLE(C) and kLI(C) for CO,.…”

Section: Distribution Of This Document Is Unlimited --mentioning

confidence: 99%

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The influence of bubble plumes on air‐seawater gas transfer velocities

Asher¹,

Karle²,

Higgins³

et al. 1996

J. Geophys. Res.

114

103

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Laboratory results have demonstrated that bubble plumes are a very efficient air‐water gas transfer mechanism. Because breaking waves generate bubble plumes, it could be possible to correlate the air‐sea gas transport velocity kL with whitecap coverage. This correlation would then allow kL to be predicted from measurements of apparent microwave brightness temperature through the increase in sea surface microwave emissivity associated with breaking waves. In order to develop this remote‐sensing‐based method for predicting air‐sea gas fluxes, a whitecap simulation tank was used to measure evasive and invasive kL values for air‐seawater transfer of carbon dioxide, oxygen, helium, sulfur hexafluoride, and dimethyl sulfide at cleaned and surfactant‐influenced water surfaces. An empirical model has been developed that can predict kL from bubble plume coverage, diffusivity, and solubility. The observed dependence of kL on molecular diffusivity and aqueous‐phase solubility agrees with the predictions of modeling studies of bubble‐driven air‐water gas transfer. It has also been shown that soluble surfactants can decrease kL even in the presence of breaking waves.

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Section: Distribution Of This Document Is Unlimited --mentioning

confidence: 96%

Section: Distribution Of This Document Is Unlimited --mentioning

confidence: 99%

The influence of bubble plumes on air‐seawater gas transfer velocities

Asher¹,

Karle²,

Higgins³

et al. 1996

J. Geophys. Res.

114

103

View full text Add to dashboard Cite

show abstract

“…From this decay rate, we can estimate an average bubble velocity by assuming that the path of the bubbles is given by the distance the bubble has to rise to reach the surface, which corresponds to the average penetration depth of the bubble cloud, say h. Thus we define the scale Figure 8b for three plunging breakers. The rise velocity of a bubble of radius r in clean water (for radius larger than 100µm) is given by Woolf & Thorpe (1991) (see also Thorpe (1982) for a review of bubble rise velocities),…”

Section: Decay Time and Rising Velocitiesmentioning

confidence: 99%

“…Note that while we have compared W to the rise velocity in clean water, we have here to consider the rise velocity in dirty water. The rise velocity is then given by the formula from Thorpe (1982) and Woolf & Thorpe (1991) for a bubble rising in dirty water …”

Section: Normalized Bubble Size Distribution and Bubble Cloud Constantmentioning

confidence: 99%

Air entrainment and bubble statistics in breaking waves

2016

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We investigate air entrainment and bubble statistics in three-dimensional breaking waves through novel direct numerical simulations of the two-phase air-water flow, resolving the length scales relevant for the bubble formation problem, the capillary length and the Hinze scale. The dissipation due to breaking is found to be in good agreement with previous experimental observations and inertial-scaling arguments. The air-entrainment properties and bubble-size statistics are investigated for various initial characteristic wave slopes. For radii larger than the Hinze scale, the bubble size distribution, can be described by N (r, t) = B(V 0 /2π)(ε(t − ∆τ )/W g)r −10/3 r −2/3 m during the active breaking stages, where ε(t − ∆τ ) is the time dependent turbulent dissipation rate, with ∆τ the collapse time of the initial air pocket entrained by the breaking wave, W a weighted vertical velocity of the bubble plume, r m the maximum bubble radius, g gravity, V 0 the initial volume of air entrained, r the bubble radius and B a dimensionless constant. The active breaking time-averaged bubble size distribution is described bȳ N (r) = B(1/2π)( l L c /W gρ)r −10/3 r −2/3 m , where l is the wave dissipation rate per unit length of breaking crest, ρ the water density and L c the length of breaking crest. Finally, the averaged total volume of entrained air,V , per breaking event can be simply related to l byV = B( l L c /W gρ), which leads to a relationship to a characteristic slope, S, of V ∝ S 5/2 . We propose a phenomenological turbulent bubble break-up model, based on earlier models and the balance between mechanical dissipation and work done against buoyancy forces. The model is consistent with the numerical results and existing experimental results.

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“…(1) with 60 s time steps to simulate CH 4 diffusion from trapped bubbles into the upper layer of the water column. We calculated that typical ebullition bubbles in Goldstream Lake (6.3 ± 0.2 mm bubble diameter measured at the lake surface, mean ± standard deviation, n = 433) lose < 1 % of their CH 4 during their ascent through the ≤ 2.9 m water column (Woolf and Thorpe, 1991;Holocher et al, 2003), which is significantly less than the difference in CH 4 contents of fresh and encapsulated bubbles (Sect. 2.2.6).…”

Section: Methane Dissolution From Bubblesmentioning

confidence: 99%

Modeling the impediment of methane ebullition bubbles by seasonal lake ice

et al. 2014

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Abstract. Microbial methane (CH 4 ) ebullition (bubbling) from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS) constitutes a novel mode of CH 4 emission. Before bubbles are encapsulated by downward-growing ice, some of their CH 4 dissolves into the lake water, where it may be subject to oxidation. We present field characterization and a model of the annual CH 4 cycle in Goldstream Lake, a thermokarst (thaw) lake in interior Alaska. We find that summertime ebullition dominates annual CH 4 emissions to the atmosphere. Eighty percent of CH 4 in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH 4 ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH 4 is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH 4 dissolution from trapped bubbles, and greater CH 4 emissions from northern lakes.

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Bubbles and the air-sea exchange of gases in near-saturation conditions

Cited by 251 publications

References 0 publications

The influence of bubble plumes on air‐seawater gas transfer velocities

The influence of bubble plumes on air‐seawater gas transfer velocities

Air entrainment and bubble statistics in breaking waves

Modeling the impediment of methane ebullition bubbles by seasonal lake ice

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