Air-Sea CO2-Exchange in a Large Annular Wind-Wave Tank and the Effects of Surfactants

Ribas-Ribas, Mariana; Helleis, Frank; Rahlff, Janina; Wurl, Oliver

doi:10.3389/fmars.2018.00457

Cited by 23 publications

(31 citation statements)

References 70 publications

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“…Zhang and Cai [16] used a nonzero intercept of 10 cm h −1 from various studies. This is in agreement with the nonzero intercept of 10.7 cm h −1 reported by Ribas-Ribas, et al [15] . This is the reason why we added this to W and K. For the Sniffle data analysis in Section 3.1, for clarity and brevity, we only compared the nonzero intercept parameterization from this study with the conventional parameterization from Wanninkhof.…”

Section: Use and Description Of Parameterizationssupporting

confidence: 94%

“…We tested the original parameterization described by Wanninkhof [3] (W) and the parameterization from this study (M) with slightly lower slopes than W based on in situ Sniffle data. We then tested (i) the original parameterization described by Wanninkhof [3] (W), (ii) the parameterization from this study (M), (iii) the parameterization described by Wanninkhof [3] with the addition of a 10.7 cm h −1 intercept (W+I) as reported in Ribas-Ribas, et al [15] (iv) the original parameterization described by Krakauer, et al [32] (K), and (v) the parameterization described by Krakauer, et al [32] with the addition of an 11 cm h −1 intercept (K+I) for the surface ocean observation-based method. Finally, we modified the Bern3D Ocean Model [34] with K and K+I.…”

Section: Use and Description Of Parameterizationsmentioning

confidence: 99%

“…Parameterizations with a nonzero intercept have been reported in [9][10][11][12][13][14][15], and the nonzero intercept ranges from 1 to 15 cm h −1 . Gas transfer velocity is unlikely to approach zero during low wind conditions as the wind speed is not the only main factor driving gas transfer across the surface; surface currents, buoyancy fluxes, micro breaking waves, and the presence of surface films (i.e., sea surface microlayer) affect gas transfer as well [3].…”

Section: Introductionmentioning

confidence: 99%

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Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO2 Fluxes

et al. 2019

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Carbon dioxide (CO2) fluxes between the ocean and atmosphere (FCO2) are commonly computed from differences between their partial pressures of CO2 (ΔpCO2) and the gas transfer velocity (k). Commonly used wind-based parameterizations for k imply a zero intercept, although in situ field data below 4 m s−1 are scarce. Considering a global average wind speed over the ocean of 6.6 m s−1, a nonzero intercept might have a significant impact on global FCO2. Here, we present a database of 245 in situ measurements of k obtained with the floating chamber technique (Sniffle), 190 of which have wind speeds lower than 4 m s−1. A quadratic parameterization with wind speed and a nonzero intercept resulted in the best fit for k. We further tested FCO2 calculated with a different parameterization with a complementary pCO2 observation-based product. Furthermore, we ran a simulation in a well-tested ocean model of intermediate complexity to test the implications of different gas transfer velocity parameterizations for the natural carbon cycle. The global ocean observation-based analysis suggests that ignoring a nonzero intercept results in an ocean-sink increase of 0.73 Gt C yr−1. This corresponds to a 28% higher uptake of CO2 compared with the flux calculated from a parameterization with a nonzero intercept. The differences in FCO2 were higher in the case of low wind conditions and large ΔpCO2 between the ocean and atmosphere. Such conditions occur frequently in the Tropics.

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Section: Use and Description Of Parameterizationssupporting

confidence: 94%

Section: Use and Description Of Parameterizationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO2 Fluxes

et al. 2019

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“…One major prerequisite for foam formation are SAS, representing a complex mixture of mainly organic compounds. Due to their amphipathic nature, SAS accumulate at the sea surface (Wurl, et al 2009) and influence CO2 air-sea gas exchange (Pereira, et al 2018;Ribas-Ribas, et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Sea foams are ephemeral hotspots for distinctive bacterial communities contrasting sea-surface microlayer and underlying surface water

Rahlff

Stolle

Giebel

et al. 2019

Preprint

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The occurrence of foams at oceans’ surfaces is patchy and generally short-lived. However, a detailed understanding of bacterial communities inhabiting foams is lacking. In this study, we investigate if marine foams differ from the sea-surface microlayer (SML), a <1 mm thick layer at the air-sea interface. The comparison of marine foams, SML and underlying water collected from the North Sea and Timor Sea showed that foams were often characterized by highest abundance of small phototrophic and prokaryotic cells as well as highest concentrations of surface-active substances (SAS). Amplicon sequencing based on 16S rRNA revealed a comparable bacterial community in SML and foam. DNA and rRNA based sequence data suggest that Pseudoalteromonas, a typical member of the SML, was highly active and thus might enhance foam formation and stability by producing SAS. Although foams contained some specific taxa, our study supports the hypothesis that foam represents a compressed version of the SML. Foam is characterized by increased cell numbers, high SAS concentration, and a significant fraction of overlapping bacteria with SML. Due to the compressed nature of foam and SML compared to the underlying water, bacteria thriving in both surface phenomena have likely implications for biogeochemical cycling and air-sea exchange processes.One-sentence summaryWhile foams at the oceans’ surface have a unique bacterial community signature, they represent a compressed version of the sea-surface microlayer with typical bacterial inhabitants.

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“…However, most radars are shore-based, or based on fixed platforms at present. To expand the observation scope of ocean waves and provide more continuous wave observation data [2][3][4][5], research on radar based on offshore mobile platforms is of great significance.…”

Section: Introductionmentioning

confidence: 99%

Wave Height and Wave Period Derived from a Shipboard Coherent S-Band Wave Radar in the South China Sea

Chen

Zhao

et al. 2019

Remote Sensing

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To expand the scope of ocean wave observations, a shipboard coherent S-band wave radar system was developed recently. The radar directly measures the wave orbital velocity from the Doppler shift of the received radar signal. The sources of this Doppler shift are analyzed. After removing the Doppler shifts caused by the ocean current and platform, the radial velocities of water particles of the surface gravity waves are retrieved. Subsequently, the wavenumber spectrum can be obtained based on linear wave theory. Later, the significant wave height and wave periods (including mean wave period and peak wave period) can be calculated from the wavenumber spectrum. This radar provides a calibration-free way to measure wave parameters and is a novel underway coherent microwave wave radar. From 9 September to 11 September, 2018, an experiment involving radar-derived and buoy-measured wave measurements was conducted in the South China Sea. The Doppler spectra obtained when the ship was in the state of navigation or mooring indicated that the quality of the radar echo was fairly good. The significant wave heights and wave periods measured using the radar are compared with those obtained from the wave buoy. The correlation coefficients of wave heights and mean wave periods between these two instruments both exceed 0.9 while the root mean square differences are respectively less than 0.15 m and 0.25 s, regardless of the state of motion of the ship. These results indicate that this radar has the capability to accurately measure ocean wave heights and wave periods.

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Air-Sea CO2-Exchange in a Large Annular Wind-Wave Tank and the Effects of Surfactants

Cited by 23 publications

References 70 publications

Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO2 Fluxes

Impact of Nonzero Intercept Gas Transfer Velocity Parameterizations on Global and Regional Ocean–Atmosphere CO2 Fluxes

Sea foams are ephemeral hotspots for distinctive bacterial communities contrasting sea-surface microlayer and underlying surface water

Wave Height and Wave Period Derived from a Shipboard Coherent S-Band Wave Radar in the South China Sea

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