Bubble Clouds in Coastal Waters and Their Role in Air-Water Gas Exchange of CO2

Crosswell, Joseph R.

doi:10.3390/jmse3030866

Cited by 4 publications

(3 citation statements)

References 83 publications

(154 reference statements)

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“…Rapid carbon fluxes have been observed during tidal and wind-driven mixing events (Sin et al 1999;Abril et al 2004;Crosswell et al 2014). These episodic fluxes are difficult to measure but may be a significant component of annual carbon budgets (Crosswell 2015).…”

Section: Spatial Scales Of Metabolic Balancementioning

confidence: 99%

Carbon budget of a shallow, lagoonal estuary: Transformations and source‐sink dynamics along the river‐estuary‐ocean continuum

Crosswell

Anderson

Stanhope

et al. 2017

Limnology & Oceanography

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A comprehensive carbon budget was constructed to quantify carbon flows through the freshwater‐marine continuum of a temperate, microtidal estuary. We performed coordinated measurements of dissolved inorganic carbon and total organic carbon fluxes to resolve spatial variability between and along the channel and shoals and diel variability across the entire estuary for 2 yr. Net ecosystem metabolism (NEM) was the most significant control on carbon flow within estuary regions. However, metabolic rates were spatially coupled such that counteracting fluxes across the channel‐shoal gradient or along the river‐ocean gradient resulted in system‐wide NEM that was closely in balance (–3.0 ± 3.3 to 1.1 ± 4.4 molC m−2 yr−1). Similarly, large diel and seasonal variability in air–water CO2 fluxes were observed during 72 spatial surveys, but these short‐term variations generally cancelled out when aggregated to annual budget terms. Although atmospheric exchanges were small (–0.2 ± 0.1 to 2.0 ± 0.4 molC m−2 yr−1), they were subject to large errors (± 4 molC m−2 yr−1) if diel variability was neglected. Internal mechanisms that maintained balanced carbon flows were strongly impacted by river discharge and were only apparent by separately quantifying channel and shoal fluxes. Notably, metabolic responses of the shoal to river forcing outweighed the responses of the channel, and the net impact was contrary to prior relationships derived from synthesis of lower‐resolution carbon budgets. Our budget demonstrates that resolution of carbon fluxes at appropriate scales, including channel‐shoal and diel variability, is critical to characterizing ecosystem function and the fate of carbon within the river‐ocean continuum.

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Section: Spatial Scales Of Metabolic Balancementioning

confidence: 99%

Carbon budget of a shallow, lagoonal estuary: Transformations and source‐sink dynamics along the river‐estuary‐ocean continuum

Crosswell

Anderson

Stanhope

et al. 2017

Limnology & Oceanography

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“…These mechanisms include bubble processes, turbulence generated from bottom stress or buoyancy fluxes, and fetch limitation of wind‐driven turbulence (Crosswell, ; MacIntyre et al, ; Vachon & Prairie, ). A further limitation of many existing gas exchange parameterizations in these settings is that they are derived using the efflux of a single gas such as sulfur hexafluoride, carbon dioxide (CO 2 ), or methane (CH 4 ) (Cole et al, ).…”

Section: Introductionmentioning

confidence: 99%

Using Noble Gases to Compare Parameterizations of Air‐Water Gas Exchange and to Constrain Oxygen Losses by Ebullition in a Shallow Aquatic Environment

et al. 2018

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Accurate determination of air-water gas exchange fluxes is critically important for calculating ecosystem metabolism rates from dissolved oxygen in shallow aquatic environments. We present a unique data set of the noble gases neon, argon, krypton, and xenon in a salt marsh pond to demonstrate how the dissolved noble gases can be used to quantify gas transfer processes and evaluate gas exchange parameterizations in shallow, near-shore environments. These noble gases are sensitive to a variety of physical processes, including bubbling. We thus additionally use this data set to demonstrate how dissolved noble gases can be used to assess the contribution of bubbling from the sediments (ebullition) to gas fluxes. We find that while literature gas exchange parameterizations do well in modeling more soluble gases, ebullition must be accounted for in order to correctly calculate fluxes of the lighter noble gases. In particular, for neon and argon, the ebullition flux is larger than the differences in the diffusive gas exchange flux estimated by four different wind speed-based parameterizations for gas exchange. We present an application of noble gas derived ebullition rates to improve estimates of oxygen metabolic fluxes in this shallow pond environment. Up to 21% of daily net oxygen production by photosynthesis may be lost from the pond via ebullition during some periods of biologically and physically produced supersaturation. Ebullition could be an important flux of oxygen and other gases that is measurable with noble gases in other shallow aquatic environments.

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“…In rivers and streams, turbulence reaching the air‐water interface is largely generated by friction with the bottom (Ho et al, ; Maurice et al, ; Raymond & Cole, ; Zappa et al, ). Additional factors include variable fetch (Vachon & Prairie, ; Woolf, ), turbidity (Abril et al, ), wave breaking (Crosswell, ; Liang et al, ; Wanninkhof et al, ; Woolf, ), the presence of biological surfactants (Lee & Saylor, ; McKenna & McGillis, ; Pereira et al, ; Wanninkhof et al, ), waterside thermal convection (Andersson et al, ; MacIntyre et al, ; Podgrajsek, Sahlée, Bastviken, et al, ; Podgrajsek, Sahlée, & Rutgersson, ), and chemical enhancement of CO 2 exchange at high pH (Smith, ; Wanninkhof, ).…”

Section: Introductionmentioning

confidence: 99%

Parameterizing Air‐Water Gas Exchange in the Shallow, Microtidal New River Estuary

2019

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Estuarine CO2 emissions are important components of regional and global carbon budgets, but assessments of this flux are plagued by uncertainties associated with gas transfer velocity (k) parameterization. We combined direct eddy covariance measurements of CO2 flux with waterside pCO2 determinations to generate more reliable k parameterizations for use in small estuaries. When all data were aggregated, k was described well by a linear relationship with wind speed (U10), in a manner consistent with prior open ocean and estuarine k parameterizations. However, k was significantly greater at night and under low wind speed, and nighttime k was best predicted by a parabolic, rather than linear, relationship with U10. We explored the effect of waterside thermal convection but found only a weak correlation between convective scale and k. Hence, while convective forcing may be important at times, it appears that factors besides waterside thermal convection were likely responsible for the bulk of the observed nighttime enhancement in k. Regardless of source, we show that these day‐night differences in k should be accounted for when CO2 emissions are assessed over short time scales or when pCO2 is constant and U10 varies. On the other hand, when temporal variability in pCO2 is large, it exerts greater control over CO2 fluxes than does k parameterization. In these cases, the use of a single k value or a simple linear relationship with U10 is often sufficient. This study provides important guidance for k parameterization in shallow or microtidal estuaries, especially when diel processes are considered.

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Bubble Clouds in Coastal Waters and Their Role in Air-Water Gas Exchange of CO2

Cited by 4 publications

References 83 publications

Carbon budget of a shallow, lagoonal estuary: Transformations and source‐sink dynamics along the river‐estuary‐ocean continuum

Carbon budget of a shallow, lagoonal estuary: Transformations and source‐sink dynamics along the river‐estuary‐ocean continuum

Using Noble Gases to Compare Parameterizations of Air‐Water Gas Exchange and to Constrain Oxygen Losses by Ebullition in a Shallow Aquatic Environment

Parameterizing Air‐Water Gas Exchange in the Shallow, Microtidal New River Estuary

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