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1. Gas Transfer Across Air‐Water Interfaces in Inland Waters: From Micro‐Eddies to Super‐Statistics

   https://doi.org/10.1029/2023WR036615  

   Katul, Gabriel; Bragg, Andrew; Mammarella, Ivan; Liu, Heping; Li, Qi; Bou‐Zeid, Elie (November 2024, Water Resources Research)

   Abstract In inland water covering lakes, reservoirs, and ponds, the gas exchange of slightly soluble gases such as carbon dioxide, dimethyl sulfide, methane, or oxygen across a clean and nearly flat air‐water interface is routinely described using a water‐side mean gas transfer velocity , where overline indicates time or ensemble averaging. The micro‐eddy surface renewal model predicts , where is the molecular Schmidt number, is the water kinematic viscosity, and is the waterside mean turbulent kinetic energy dissipation rate at or near the interface. While has been reported across a number of data sets, others report large scatter or variability around this value range. It is shown here that this scatter can be partly explained by high temporal variability in instantaneous around , a mechanism that was not previously considered. As the coefficient of variation in increases, must be adjusted by a multiplier that was derived from a log‐normal model for the probability density function of . Reported variations in with a macro‐scale Reynolds number can also be partly attributed to intermittency effects in . Such intermittency is characterized by the long‐range (i.e., power‐law decay) spatial auto‐correlation function of . That varies with a macro‐scale Reynolds number does not necessarily violate the micro‐eddy model. Instead, it points to a coordination between the macro‐ and micro‐scales arising from the transfer of energy across scales in the energy cascade. 

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2. From Substrate to Surface: A Turbulence‐Based Model for Gas Transfer Across Sediment‐Water‐Air Interfaces in Vegetated Streams

   https://doi.org/10.1029/2021WR030776  

   Tseng, Chien‐Yung; Tinoco, Rafael O. (January 2022, Water Resources Research)
3. Short-term variations in air-water gas transfer velocity and CO ₂ fluxes over a temperate seagrass meadow

   https://doi.org/10.5194/egusphere-2026-4232  

   Granville, Kayleigh E; Berg, Peter (August 2026, Copernicus Publications, European Geosciences Union)

   Abstract. Seagrass meadows store and sequester carbon for long periods of time in their tissues and sediments. They can also emit or take up gases such as carbon dioxide (CO2) across the air-water interface. Air-water gas fluxes over seagrass meadows are poorly constrained, primarily due to methodological limitations and a persistent lack of fine-scale in situ spatial and temporal data. In this study, we present a thorough assessment of air-water CO2 flux dynamics over a shallow, temperate coastal bay (South Bay, Virginia, USA) that has a benthic environment dominated by a temperate eelgrass meadow (Zostera marina). We evaluated major sources of variability in the flux calculation by analyzing in situ and regional wind speeds, comparing in situ and modeled gas transfer velocities (k600), and conducting a long-term flux study to disentangle diurnal CO2 flux patterns over South Bay. All wind stations located in proximity to land features significantly underestimated wind speeds over South Bay, while a wind station located in a nearby estuary over open water (Chesapeake Bay) was most representative of in situ wind speed measurements. We also derived in situ k600 by deploying an “upside-down” aquatic eddy covariance system right below the air-water interface and using the data to ground truth the best-fitting empirical parameterizations for our site. The best-fitting models for South Bay were originally derived over the ocean and had an intercept of zero. Using the best-fitting model and continuous water column  measurements, we derived hourly air-water CO2 fluxes over South Bay during the peak seagrass density period (early July) over three years. CO2 fluxes exhibited a distinct diurnal pattern that correlated well with photosynthetically active radiation, demonstrating that fluxes are driven by photosynthesis and respiration from photosynthetic organisms, seagrasses, epiphytes, benthic microalgae and water column microalgae. Overall, South Bay was a small sink of CO2 (−0.60 mmol CO2 m−2 d−1) during the peak seagrass period across all three years. Due to the continuous nature of our study, we were able to derive CO2 flux estimates during a storm period. South Bay was a source of CO2 during the storm. When the storm period was removed and only fair-weather data were considered, South Bay was a larger sink of CO2 (−4.20 mmol CO2 m−2 d−1). Our results underline the importance of evaluating air-water gas fluxes over multiple day-night cycles and during multiple weather conditions. 

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4. Kinetic and equilibrium fractionation of O2 isotopologues during air-water gas transfer and implications for tracing oxygen cycling in the ocean

   https://doi.org/10.1016/j.marchem.2019.02.006  

   Li, Boda; Yeung, Laurence Y.; Hu, Huanting; Ash, Jeanine L. (March 2019, Marine Chemistry)
5. Turbulence in a small boreal lake: Consequences for air–water gas exchange

   https://doi.org/10.1002/lno.11645  

   MacIntyre, Sally; Bastviken, David; Arneborg, Lars; Crowe, Adam T.; Karlsson, Jan; Andersson, Andreas; Gålfalk, Magnus; Rutgersson, Anna; Podgrajsek, Eva; Melack, John M. (January 2020, Limnology and Oceanography)

   null (Ed.)

   The hydrodynamics within small boreal lakes have rarely been studied, yet knowing whether turbulence at the air-water interface and in the water column scales with metrics developed elsewhere is essential for computing metabolism and fluxes of climate-forcing trace gases. We instrumented a humic, 4.7 ha, boreal lake with 2 meteorological stations, 3 thermistor arrays, an infra-red (IR) camera to quantify surface divergence, obtained turbulence as dissipation rate of turbulent kinetic energy (ε) using an acoustic Doppler velocimeter and a temperature-gradient microstructure profiler, and conducted chamber measurements for short periods to obtain fluxes and gas transfer velocities (k). Near-surface ε varied from 10-8 m2 s-3 to 10-6 m2 s-3 for the 0 to 4 m s-1 winds and followed predictions from Monin-Obukhov similarity theory. The coefficient of eddy diffusivity in the mixed layer was up to 10-3 m2 s-1 on the windiest afternoons, an order of magnitude less other afternoons, and near molecular at deeper depths. The upper thermocline upwelled when Lake numbers (LN) dropped below 4 facilitating vertical and horizontal exchange. k computed from a surface renewal model using ε agreed with values from chambers and surface divergence and increased linearly with wind speed. Diurnal thermoclines formed on sunny days when winds were < 3 m s-1, a condition that can lead to elevated near-surface ε and k. Results extend scaling approaches developed in the laboratory and for larger water bodies, illustrate turbulence and k are greater than expected in small wind-sheltered lakes, and provide new equations to quantify fluxes. 

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