Measurement of air–water CO2 transfer at four coastal sites using a chamber method

Tokoro, Tatsuki; Watanabe, Atsushi; Nadaoka, Kazuo; Tamura, Hitoshi; Nozaki, Ken; Kato, Ken; Negishi, Akira

doi:10.1016/j.jmarsys.2006.04.010

Cited by 21 publications

(16 citation statements)

References 23 publications

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“…For the data gap between two water side measurements, the time series of dissolved CO 2 was approximated through linear interpolation from the preincubation and postincubation concentration as described in Tokoro et al . []. The 90% response time for aqueous CO 2 measurement is less than 90 s. The flux of CO 2 as a function of time was calculated as:

F (t) = \frac{d C}{d t} \frac{V}{S},

where

\frac{d C}{d t}

is the change of CO 2 concentration inside of the chamber (in units of mol/L), and the concentration of CO 2 was obtained from the measured partial pressure.…”

Section: Methodsmentioning

confidence: 99%

On the coefficients of small eddy and surface divergence models for the air‐water gas transfer velocity

et al. 2015

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Recent studies suggested that under low to moderate wind conditions without bubble entraining wave breaking, the air-water gas transfer velocity k 1 can be mechanistically parameterized by the nearsurface turbulence, following the small eddy model (SEM). Field measurements have supported this model in a variety of environmental forcing systems. Alternatively, surface divergence model (SDM) has also been shown to predict the gas transfer velocity across the air-water interface in laboratory settings. However, the empirically determined model coefficients (a in SEM and c 1 in SDM) scattered over a wide range. Here we present the first field measurement of the near-surface turbulence with a novel floating PIV system on Lake Michigan, which allows us to evaluate the SEM and SDM in situ in the natural environment. k 1 was derived from the CO 2 flux that was measured simultaneously with a floating gas chamber. Measured results indicate that a and c 1 are not universal constants. Regression analysis showed that a $ logðeÞ while the near-surface turbulence dissipation rate e is approximately greater than 10 26 m 2 s 23 according to data measured for this study as well as from other published results measured in similar environments or in laboratory settings. It also showed that a scales linearly with the turbulent Reynolds number. Similarly, coefficient c 1 in the SDM was found to linearly scale with the Reynolds number. These findings suggest that larger eddies are also important parameters, and the dissipation rate in the SEM or the surface divergence b 0 in the SDM alone may not be adequate to determine k 1 completely.

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F (t) = \frac{d C}{d t} \frac{V}{S},

where

\frac{d C}{d t}

is the change of CO 2 concentration inside of the chamber (in units of mol/L), and the concentration of CO 2 was obtained from the measured partial pressure.…”

Section: Methodsmentioning

confidence: 99%

On the coefficients of small eddy and surface divergence models for the air‐water gas transfer velocity

et al. 2015

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“…The fCO 2 analyser mentioned above was connected to the chamber by a Teflon tube for measurement of fCO 2 inside the chamber. Details of this method are described elsewhere (Tokoro et al ., , ). The validity of the method has been quantitatively confirmed by a comparison of turbulence near the water surface inside and outside of the floating chamber (Tokoro et al ., ; Vachon et al ., ).…”

Section: Methodsmentioning

confidence: 99%

Net uptake of atmospheric CO ₂ by coastal submerged aquatic vegetation

et al. 2014

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‘Blue Carbon’, which is carbon captured by marine living organisms, has recently been highlighted as a new option for climate change mitigation initiatives. In particular, coastal ecosystems have been recognized as significant carbon stocks because of their high burial rates and long-term sequestration of carbon. However, the direct contribution of Blue Carbon to the uptake of atmospheric CO2 through air-sea gas exchange remains unclear. We performed in situ measurements of carbon flows, including air-sea CO2 fluxes, dissolved inorganic carbon changes, net ecosystem production, and carbon burial rates in the boreal (Furen), temperate (Kurihama), and subtropical (Fukido) seagrass meadows of Japan from 2010 to 2013. In particular, the air-sea CO2 flux was measured using three methods: the bulk formula method, the floating chamber method, and the eddy covariance method. Our empirical results show that submerged autotrophic vegetation in shallow coastal waters can be functionally a sink for atmospheric CO2. This finding is contrary to the conventional perception that most near-shore ecosystems are sources of atmospheric CO2. The key factor determining whether or not coastal ecosystems directly decrease the concentration of atmospheric CO2 may be net ecosystem production. This study thus identifies a new ecosystem function of coastal vegetated systems; they are direct sinks of atmospheric CO2.

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“…The floating chamber (FC) technique has been used in previous studies (Borges et al, 2004a;Tokoro et al, 2007;Vachon et al, 2010) to provide estimates of gas transfer velocity at short time scales (~20 minutes). The FC has been criticized by several researchers because the chamber covers the water surface and eliminates wind stress (Raymond and Cole, 2001) and because interference from the chamber itself results in artificially higher estimates of transfer velocity (Borges et al, 2004b).…”

Section: Introductionmentioning

confidence: 99%

“…The FC has been criticized by several researchers because the chamber covers the water surface and eliminates wind stress (Raymond and Cole, 2001) and because interference from the chamber itself results in artificially higher estimates of transfer velocity (Borges et al, 2004b). Tokoro et al (2007) pointed out that comparison of turbulent conditions inside and outside of the chamber's perimeter is needed to determine gas exchange velocities quantitatively using the FC technique. Tokoro et al (2008) measured turbulent kinetic energy (TKE) inside and outside a chamber's perimeter using a single acoustic Doppler velocimeter (ADV).…”

Section: Introductionmentioning

confidence: 99%

Sniffle: a step forward to measure in situ CO2 fluxes with the floating chamber technique

Ribas-Ribas¹,

Kilcher

Wurl³

2018

Elementa: Science of the Anthropocene

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Understanding how the ocean absorbs anthropogenic CO 2 is critical for predicting climate change. We designed Sniffle, a new autonomous drifting buoy with a floating chamber, to measure gas transfer velocities and air-sea CO 2 fluxes with high spatiotemporal resolution. Currently, insufficient in situ data exist to verify gas transfer parameterizations at low wind speeds (<4 m s −1 ), which leads to underestimation of gas transfer velocities and, therefore, of air-sea CO 2 fluxes. The Sniffle is equipped with a sensor to consecutively measure aqueous and atmospheric pCO 2 and to monitor increases or decreases of CO 2 inside the chamber. During autonomous operation, a complete cycle lasts 40 minutes, with a new cycle initiated after flushing the chamber. The Sniffle can be deployed for up to 15 hours at wind speeds up to 10 m s −1. Floating chambers often overestimate fluxes because they create additional turbulence at the water surface. We correct fluxes by measuring turbulence with two acoustic Doppler velocimeters, one positioned directly under the floating chamber and the other positioned sideways, to compare artificial disturbance caused by the chamber and natural turbulence. The first results of deployment in the North Sea during the summer of 2016 demonstrate that the new drifting buoy is a useful tool that can improve our understanding of gas transfer velocity with in situ measurements. At low and moderate wind speeds and different conditions, the results obtained indicate that the observed tidal basin was acting as a source of atmospheric CO 2 . Wind speed and turbulence alone could not fully explain the variance in gas transfer velocity. We suggest that other factors like surfactants, rain or tidal current will have an impact on gas transfer parameterizations.

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Measurement of air–water CO2 transfer at four coastal sites using a chamber method

Cited by 21 publications

References 23 publications

On the coefficients of small eddy and surface divergence models for the air‐water gas transfer velocity

On the coefficients of small eddy and surface divergence models for the air‐water gas transfer velocity

Net uptake of atmospheric CO ₂ by coastal submerged aquatic vegetation

Sniffle: a step forward to measure in situ CO2 fluxes with the floating chamber technique

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Measurement of air–water CO2 transfer at four coastal sites using a chamber method

Cited by 21 publications

References 23 publications

On the coefficients of small eddy and surface divergence models for the air‐water gas transfer velocity

On the coefficients of small eddy and surface divergence models for the air‐water gas transfer velocity

Net uptake of atmospheric CO 2 by coastal submerged aquatic vegetation

Sniffle: a step forward to measure in situ CO2 fluxes with the floating chamber technique

Contact Info

Product

Resources

About

Net uptake of atmospheric CO ₂ by coastal submerged aquatic vegetation