Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank

Nagel, Leila; Krall, Kerstin E.; Jähne, Bernd

doi:10.5194/os-11-111-2015

Cited by 17 publications

(28 citation statements)

References 25 publications

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“…The Aeolotron (Heidelberg, Germany) is a large-scale annular wind-wave facility with a total height of 2.4 m, and an outer diameter of 10 m. The wind speed inside the channel was measured using a Pitot tube and anemometer. A more detailed description of the facility is given by Nagel et al (2015). The friction velocity U was determined and converted into the value U 10 as described in Maximilian Bopp and Bernd Jähne (unpublished, 2014), with U 10 being the equivalent wind speed at 10 m height above the ocean.…”

Section: Methodsmentioning

confidence: 99%

Effect of wind speed on the size distribution of gel particles in the sea surface microlayer: insights from a wind–wave channel experiment

2018

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Abstract. Gel particles, such as transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP), are important organic components in the sea surface microlayer (SML). Here, we present results on the effect of different wind speeds on the accumulation and size distribution of TEP and CSP during a wind wave channel experiment in the Aeolotron. Total areas of TEP (TEP SML ) and CSP (CSP SML ) in the surface microlayer were exponentially related to wind speed. At wind speeds < 6 m s −1 , accumulation of TEP SML and CSP SML occurred, decreasing at wind speeds of > 8 m s −1 . Wind speeds > 8 m s −1 also significantly altered the size distribution of TEP SML in the 2-16 µm size range towards smaller sizes. The response of the CSP SML size distribution to wind speed varied through time depending on the biogenic source of gels. Wind speeds > 8 m s −1 decreased the slope of CSP SML size distribution significantly in the absence of autotrophic growth. For the slopes of TEP and CSP size distribution in the bulk water, no significant difference was observed between high and low wind speeds. Changes in spectral slopes between high and low wind speed were higher for TEP SML than for CSP SML , indicating that the impact of wind speed on size distribution of gel particles in the SML may be more pronounced for TEP than for CSP, and that CSP SML are less prone to aggregation during the low wind speeds. Addition of an E. huxleyi culture resulted in a higher contribution of submicron gels (0.4-1 µm) in the SML at higher wind speed (> 6 m s −1 ), indicating that phytoplankton growth may potentially support the emission of submicron gels with sea spray aerosol.

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Section: Methodsmentioning

confidence: 99%

Effect of wind speed on the size distribution of gel particles in the sea surface microlayer: insights from a wind–wave channel experiment

2018

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“…The system is ideal for laboratory experiments where high-frequency sampling is beneficial, for example in studies of gas exchange and gas partitioning during ice formation and melt (Loose et al, 2009a;Lovely et al, 2015), and studies of air-water gas exchange using wind-wave tanks or bubble plume generators (Asher et al, 1996;Callaghan et al, 2014;Krall and Jähne, 2014;Mesarchaki et al, 2015b;Nagel et al, 2015). It could be used for continuous, high-frequency monitoring of surface waters in order to improve understanding of physically-driven gas fluxes, and be used alongside instruments measuring the fluxes of biologically-active gases (Cassar et al, 2009;Rafelski et al, 2015).…”

Section: Future Directionsmentioning

confidence: 99%

Insight into chemical, biological, and physical processes in coastal waters from dissolved oxygen and inert gas tracers

Manning¹

2017

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In this thesis, I use coastal measurements of dissolved O 2 and inert gases to provide insight into the chemical, biological, and physical processes that impact the oceanic cycles of carbon and dissolved gases. Dissolved O 2 concentration and triple isotopic composition trace net and gross biological productivity. The saturation states of inert gases trace physical processes, such as air-water gas exchange, temperature change, and mixing, that affect all gases.First, I developed a field-deployable system that measures Ne, Ar, Kr, and Xe gas ratios in water. It has precision and accuracy of 1 % or better, enables near-continuous measurements, and has much lower cost compared to existing laboratory-based methods. The system will increase the scientific community's access to use dissolved noble gases as environmental tracers.Second, I measured O 2 and five noble gases during a cruise in Monterey Bay, California. I developed a vertical model and found that accurately parameterizing bubble-mediated gas exchange was necessary to accurately simulate the He and Ne measurements. I present the first comparison of multiple gas tracer, incubation, and sediment trap-based productivity estimates in the coastal ocean. Net community production estimated from 15 NO -3 uptake and O 2 /Ar gave equivalent results at steady state. Underway O 2 /Ar measurements revealed submesoscale variability that was not apparent from daily incubations.Third, I quantified productivity by O 2 mass balance and air-water gas exchange by dual tracer ( 3 He/SF 6 ) release during ice melt in the Bras d'Or Lakes, a Canadian estuary. The gas transfer velocity at >90 % ice cover was 6 % of the rate for nearly ice-free conditions. Rates of volumetric gross primary production were similar when the estuary was completely ice-covered and ice-free, and the ecosystem was on average net autotrophic during ice melt and net heterotrophic following ice melt. I present a method for incorporating the isotopic composition of H 2 O into the O 2 isotope-based productivity calculations, which increases the estimated gross primary production in this study by 46-97 %.In summary, I describe a new noble gas analysis system and apply O 2 and inert gas observations in new ways to study chemical, biological, and physical processes in coastal waters.

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“…Heat transfer velocities across the aqueous viscous boundary layer can be measured actively by the use of a heat source [8,9,10,13] or passively by exploiting the effect of surface cooling due to evaporation [11,12]. The first measurements by Jähne et al [8] were done using active thermography.…”

Section: Earlier Measurement Techniquesmentioning

confidence: 99%

“…However, thermography can not only be used to visualize heat exchange, but also to derive heat transfer velocities [8][9][10][11][12][13]. As the driving mechanisms for heat and gas exchange are the same, it is possible to scale to gas transfer velocities from measured heat transfer velocities and therefore indirectly measure gas transfer velocities [13].…”

Section: Introductionmentioning

confidence: 99%

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Active thermography as a tool to investigate heat and gas transfer across the airwater interface

Kunz

Jähne

2016

Proceedings of the 2016 International Conference on Quantitative InfraRed Thermography

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Gas and heat exchange between the ocean and the atmosphere are a key process in the earth system. Active thermography is a tool that can be used to estimate heat and gas transfer rates with unprecedented temporal and spatial resolution compared to other measurement techniques. In this paper recent technical progress of this method is described: a) a spatially more homogeneous heating of the water by a carbon dioxide laser for measurements with a significant lower systematic error and statistical uncertainty, and b) a new modulation scheme for faster measurements. While the latter is essential for field measurements, the first enables the distinction of different models for air-water gas exchange in the laboratory.

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Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank

Cited by 17 publications

References 25 publications

Effect of wind speed on the size distribution of gel particles in the sea surface microlayer: insights from a wind–wave channel experiment

Effect of wind speed on the size distribution of gel particles in the sea surface microlayer: insights from a wind–wave channel experiment

Insight into chemical, biological, and physical processes in coastal waters from dissolved oxygen and inert gas tracers

Active thermography as a tool to investigate heat and gas transfer across the airwater interface

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