scholarly journals The effect of wind speed products and wind speed—gas exchange relationships on interannual variability of the air—sea CO2gas transfer velocity

Tellus B ◽  
2005 ◽  
Vol 57 (2) ◽  
pp. 95-106
Author(s):  
Are Olsen ◽  
Rik Wanninkhof ◽  
Joaquin A. Triñanes ◽  
Truls Johannessen
Keyword(s):  
Wind Speed ◽  
Gas Exchange ◽  
Interannual Variability ◽  
Exchange Relationships ◽  
Transfer Velocity

scholarly journals Evidence for surface organic matter modulation of air-sea CO<sub>2</sub> gas exchange

2009 ◽  
Vol 6 (6) ◽  
pp. 1105-1114 ◽  
Author(s):  
M. Ll. Calleja ◽  
C. M. Duarte ◽  
Y. T. Prairie ◽  
S. Agustí ◽  
G. J. Herndl
Keyword(s):  
Organic Matter ◽  
Wind Speed ◽  
Gas Exchange ◽  
Co2 Exchange ◽  
Open Ocean ◽  
Gas Transfer ◽  
Co2 Fluxes ◽  
Transfer Velocity ◽  
Gas Transfer Velocity

Abstract. Air-sea CO2 exchange depends on the air-sea CO2 gradient and the gas transfer velocity (k), computed as a function of wind speed. Large discrepancies among relationships predicting k from wind suggest that other processes also contribute significantly to modulate CO2 exchange. Here we report, on the basis of the relationship between the measured gas transfer velocity and the organic carbon concentration at the ocean surface, a significant role of surface organic matter in suppressing air-sea gas exchange, at low and intermediate winds, in the open ocean, confirming previous observations. The potential role of total surface organic matter concentration (TOC) on gas transfer velocity (k) was evaluated by direct measurements of air-sea CO2 fluxes at different wind speeds and locations in the open ocean. According to the results obtained, high surface organic matter contents may lead to lower air-sea CO2 fluxes, for a given air-sea CO2 partial pressure gradient and wind speed below 5 m s−1, compared to that observed at low organic matter contents. We found the bias in calculated gas fluxes resulting from neglecting TOC to co-vary geographically and seasonally with marine productivity. These results support previous evidences that consideration of the role of organic matter in modulating air-sea CO2 exchange may improve flux estimates and help avoid possible bias associated to variability in surface organic concentration across the ocean.

Is remote sensing of the surfactant effect on gas transfer velocity possible?

2021 ◽  
Author(s):  
Jacek Piskozub ◽  
Violetta Drozdowska ◽  
Iwona Wróbel-Niedźwiecka ◽  
Przemysław Makuch ◽  
Piotr Markuszewski ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Wind Speed ◽  
Gas Exchange ◽  
Partial Pressure ◽  
Gas Transfer ◽  
Transfer Velocity ◽  
Fluorescence Parameters ◽  
Gas Transfer Velocity ◽  
Surfactant Effect ◽  
Surfactant Activity

&lt;p&gt;The air-sea gas flux is proportional to the difference of partial pressure between the sea-water and the overlying atmosphere multiplied by gas transfer velocity &lt;em&gt;k&lt;/em&gt;, a measure of the effectiveness of the gas exchange. Because wind is the source of turbulence making the gas exchange more effective, &lt;em&gt;k&lt;/em&gt; is usually parameterized by wind speed. Unfortunately, measured values of gas transfer velocity at a given wind speed have a large spread in values. Surfactants have been long suspected as the main reason of this variability but few measurements of gas exchange and surfactants have been performed at open sea simultaneously and therefore their results were inconclusive. Only recently, it has been shown that surfactants may decrease the CO&lt;sub&gt;2&lt;/sub&gt; air-sea exchange by up to 50%. However the labour intensive methods used for surfactant study make it impossible to collect enough data to map the surfactant coverage or even create a gas transfer velocity parameterization involving a measure of surfactant activity. This is why we propose to use optical fluorescence as a proxy of surfactant activity.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Previous research done by our group showed that fluorescence parameters allow estimation the surfactant enrichment of the surface microlayer, as well as types and origin of fluorescent organic matter involved. We plan to measure, from a research ship, all the variables needed for calculation of gas transfer velocity &lt;em&gt;k&lt;/em&gt; (namely CO&lt;sub&gt;2&lt;/sub&gt; partial pressure both in water and in air as well as vertical flux of this trace gas) and to use mathematical optimization methods to look for a parameterization involving wind speed and one of the fluorescence parameters which will minimize the residual &lt;em&gt;k&lt;/em&gt; variability. Although our research will still involve water sampling and laboratory fluorescence measurements, the knowledge of which absorption and fluorescence emission bands are the best proxy for surfactant activity may allow to create remote sensing products (fluorescence lidars) allowing continuous measurements of surfactant activity at least from the ship board, if not from aircraft and satellites. The improved parameterization of the CO&lt;sub&gt;2&lt;/sub&gt; gas transfer velocity will allow better constraining of basin-wide and global air-sea fluxes, an important component of global carbon budget.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;If an improved gas transfer velocity parametrization based on surfactant fluorescence spectrum in concert with a turbulence proxy (wind) were to be found, a tantalizing possibility arises of a remote sensing estimation of &lt;em&gt;k&lt;/em&gt;. Namely a UV lidar can both excite and measure the fluorescence band identified as proxy of the surfactant effect on the gas transfer velocity. Depending on the wavelength bands needed to be utilized, the effect could be measured from a moving ship (already an improvements on methods needing sampling), an aircraft or possibly even a satellite. We intend to pursue this idea in cruises to both the Baltic and the North Atlantic, possibly in cooperation with other air-sea interaction groups (this presentation is in part an invitation to cooperation).&lt;/p&gt;

Study on air-sea CO2 exchange with wave breaking

2020 ◽  
Author(s):  
Shuo Li ◽  
Alexander Babanin ◽  
Fangli Qiao ◽  
Dejun Dai ◽  
Shumin Jiang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Gas Exchange ◽  
Significant Role ◽  
Wave Breaking ◽  
Co2 Exchange ◽  
Gas Transfer ◽  
Data Sets ◽  
Transfer Velocity ◽  
Ocean Surface Waves ◽  
Hydrodynamic Processes

&lt;p&gt;Hydrodynamic processes at air-sea interface play a significant role on air-sea CO&lt;sub&gt;2&lt;/sub&gt; gas exchange, which further affects global carbon cycle and climate change. CO&lt;sub&gt;2&lt;/sub&gt; gas transfer velocity (K&lt;sub&gt;CO2&lt;/sub&gt;) is generally parameterized with wind speed but ocean surface waves have direct impact on the gas exchange. Thus, the relationship between wave breaking and CO&lt;sub&gt;2&lt;/sub&gt; gas exchange was studied through laboratory experiments and by utilizing field campaign data. The results from laboratory show that wave breaking plays a significant role in CO&lt;sub&gt;2&lt;/sub&gt; gas exchange in all experiments while wind forcing can also influence K&lt;sub&gt;CO2&lt;/sub&gt;. A non-dimensional empirical formula is established in which K&lt;sub&gt;CO2 &lt;/sub&gt;is expressed as the product of wave breaking probability, transformed Reynolds number and an enhancement factor of wind speed. The parameterization is then improved by considering the bubble-mediated gas transfer based on both laboratory and ship campaign data sets. In the end, the formula is employed in the estimation of global CO&lt;sub&gt;2&lt;/sub&gt; uptake by ocean and the result is found consistent with reported values.&lt;/p&gt;

scholarly journals Evidence for surface organic matter modulation of air-sea CO<sub>2</sub> gas exchange

2008 ◽  
Vol 5 (6) ◽  
pp. 4209-4233
Author(s):  
M. Ll. Calleja ◽  
C. M. Duarte ◽  
Y. T. Prairie ◽  
S. Agustí ◽  
G. J. Herndl
Keyword(s):  
Organic Matter ◽  
Wind Speed ◽  
Gas Exchange ◽  
Ocean Surface ◽  
Co2 Exchange ◽  
Gas Transfer ◽  
Co2 Fluxes ◽  
Transfer Velocity ◽  
Gas Transfer Velocity

Abstract. Air-sea CO2 exchange depends on the air-sea CO2 gradient and the gas transfer velocity (k), computed as a simple function of wind speed. Large discrepancies among relationships predicting k from wind suggest that other processes may also contribute significantly to modulate CO2 exchange. Here we report, on the basis of the relationship between the measured gas transfer velocity and the ocean surface organic carbon concentration at the ocean surface, a significant role of surface organic matter in suppressing air-sea gas exchange, at low and intermediate winds, in the open ocean. The potential role of total surface organic matter concentration (TOC) on gas transfer velocity (k) was evaluated by direct measurements of air-sea CO2 fluxes at different wind speeds and locations in the open ocean. According to the results obtained, high surface organic matter contents may lead to lower air-sea CO2 fluxes, for a given air-sea CO2 partial pressure gradient and wind speed below 5 m s−1, compared to that observed at low organic matter contents. We found the bias in calculated gas fluxes resulting from neglecting TOC to co-vary geographically and seasonally with marine productivity. These findings suggest that consideration of the role of organic matter in modulating air-sea CO2 exchange can improve flux estimates and help avoid possible bias associated to variability in surface organic concentration across the ocean.

scholarly journals Sea-to-air and diapycnal nitrous oxide fluxes in the eastern tropical North Atlantic Ocean

2012 ◽  
Vol 9 (3) ◽  
pp. 957-964 ◽  
Author(s):  
A. Kock ◽  
J. Schafstall ◽  
M. Dengler ◽  
P. Brandt ◽  
H. W. Bange
Keyword(s):  
Nitrous Oxide ◽  
Gas Exchange ◽  
Mixed Layer ◽  
North Atlantic Ocean ◽  
Gas Transfer ◽  
Potential Contribution ◽  
Transfer Velocity ◽  
N2o Production ◽  
Gas Transfer Velocity ◽  
Upwelled Water

Abstract. Sea-to-air and diapycnal fluxes of nitrous oxide (N2O) into the mixed layer were determined during three cruises to the upwelling region off Mauritania. Sea-to-air fluxes as well as diapycnal fluxes were elevated close to the shelf break, but elevated sea-to-air fluxes reached further offshore as a result of the offshore transport of upwelled water masses. To calculate a mixed layer budget for N2O we compared the regionally averaged sea-to-air and diapycnal fluxes and estimated the potential contribution of other processes, such as vertical advection and biological N2O production in the mixed layer. Using common parameterizations for the gas transfer velocity, the comparison of the average sea-to-air and diapycnal N2O fluxes indicated that the mean sea-to-air flux is about three to four times larger than the diapycnal flux. Neither vertical and horizontal advection nor biological production were found sufficient to close the mixed layer budget. Instead, the sea-to-air flux, calculated using a parameterization that takes into account the attenuating effect of surfactants on gas exchange, is in the same range as the diapycnal flux. From our observations we conclude that common parameterizations for the gas transfer velocity likely overestimate the air-sea gas exchange within highly productive upwelling zones.

scholarly journals Surfactant control of gas transfer velocity along an offshore coastal transect: results from a laboratory gas exchange tank

2016 ◽  
Vol 13 (13) ◽  
pp. 3981-3989 ◽  
Author(s):  
R. Pereira ◽  
K. Schneider-Zapp ◽  
R. C. Upstill-Goddard
Keyword(s):  
Organic Matter ◽  
Gas Exchange ◽  
Trace Gas ◽  
Gas Transfer ◽  
Transfer Velocity ◽  
Chl A ◽  
Gas Transfer Velocity ◽  
Biogeochemical Models ◽  
Sea Surface Microlayer ◽  
Laboratory Water

Abstract. Understanding the physical and biogeochemical controls of air–sea gas exchange is necessary for establishing biogeochemical models for predicting regional- and global-scale trace gas fluxes and feedbacks. To this end we report the results of experiments designed to constrain the effect of surfactants in the sea surface microlayer (SML) on the gas transfer velocity (kw; cm h−1), seasonally (2012–2013) along a 20 km coastal transect (North East UK). We measured total surfactant activity (SA), chromophoric dissolved organic matter (CDOM) and chlorophyll a (Chl a) in the SML and in sub-surface water (SSW) and we evaluated corresponding kw values using a custom-designed air–sea gas exchange tank. Temporal SA variability exceeded its spatial variability. Overall, SA varied 5-fold between all samples (0.08 to 0.38 mg L−1 T-X-100), being highest in the SML during summer. SML SA enrichment factors (EFs) relative to SSW were  ∼  1.0 to 1.9, except for two values (0.75; 0.89: February 2013). The range in corresponding k660 (kw for CO2 in seawater at 20 °C) was 6.8 to 22.0 cm h−1. The film factor R660 (the ratio of k660 for seawater to k660 for “clean”, i.e. surfactant-free, laboratory water) was strongly correlated with SML SA (r ≥ 0.70, p ≤ 0.002, each n = 16). High SML SA typically corresponded to k660 suppressions  ∼  14 to 51 % relative to clean laboratory water, highlighting strong spatiotemporal gradients in gas exchange due to varying surfactant in these coastal waters. Such variability should be taken account of when evaluating marine trace gas sources and sinks. Total CDOM absorbance (250 to 450 nm), the CDOM spectral slope ratio (SR = S275 − 295∕S350 − 400), the 250 : 365 nm CDOM absorption ratio (E2 : E3), and Chl a all indicated spatial and temporal signals in the quantity and composition of organic matter in the SML and SSW. This prompts us to hypothesise that spatiotemporal variation in R660 and its relationship with SA is a consequence of compositional differences in the surfactant fraction of the SML DOM pool that warrants further investigation.

scholarly journals Modelling marine emissions and atmospheric distributions of halocarbons and DMS: the influence of prescribed water concentration vs. prescribed emissions

2015 ◽  
Vol 15 (12) ◽  
pp. 17553-17598
Author(s):  
S. T. Lennartz ◽  
G. Krysztofiak-Tong ◽  
C. A. Marandino ◽  
B.-M. Sinnhuber ◽  
S. Tegtmeier ◽  
...  
Keyword(s):  
Wind Speed ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Trace Gases ◽  
Surface Wind ◽  
Water Concentration ◽  
Absolute Magnitude ◽  
Actual State ◽  
Transfer Velocity ◽  
Mixing Ratios

Abstract. Marine produced short-lived trace gases such as dibromomethane (CH2Br2), bromoform (CHBr3), methyliodide (CH3I) and dimethylsulfide (DMS) significantly impact tropospheric and stratospheric chemistry. Describing their marine emissions in atmospheric chemistry models as accurately as possible is necessary to quantify their impact on ozone depletion and the Earth's radiative budget. So far, marine emissions of trace gases have mainly been prescribed from emission climatologies, thus lacking the interaction between the actual state of the atmosphere and the ocean. Here we present simulations with the chemistry climate model EMAC with online calculation of emissions based on surface water concentrations, in contrast to directly prescribed emissions. Considering the actual state of the model atmosphere results in a concentration gradient consistent with model real-time conditions at ocean surface and atmosphere, which determine the direction and magnitude of the computed flux. This method has a number of conceptual and practical benefits, as the modelled emission can respond consistently to changes in sea surface temperature, surface wind speed, sea ice cover and especially atmospheric mixing ratio. This online calculation could enhance, dampen or even invert the fluxes (i.e. deposition instead of emissions) of VSLS. We show that differences between prescribing emissions and prescribing concentrations (−28 % for CH2Br2 to +11 % for CHBr3) result mainly from consideration of the actual, time-varying state of the atmosphere. The absolute magnitude of the differences depends mainly on the surface ocean saturation of each particular gas. Comparison to observations from aircraft, ships and ground stations reveals that computing the air–sea flux interactively leads in most of the cases to more accurate atmospheric mixing ratios in the model compared to the computation from prescribed emissions. Calculating emissions online also enables effective testing of different air–sea transfer velocity parameterizations k, which was performed here for eight different parameterizations. The testing of these different k values is of special interest for DMS, as recently published parameterizations derived by direct flux measurements using eddy covariance measurements suggest decreasing k values at high wind speeds or a linear relationship with wind speed. Implementing these parameterizations reduces discrepancies in modelled DMS atmospheric mixing ratios and observations by a factor of 1.5 compared to parameterizations with a quadratic or cubic relationship to wind speed.

Interannual Variability of Wind Speed and Wind Power at Five Tall-Tower Sites in Minnesota (1996-2001)

2003 ◽  
Vol 24 (3) ◽  
pp. 183-195 ◽  
Author(s):  
Katherine Klink ◽  
Helen D. Fisher ◽  
Geoffrey K. Force ◽  
Joanna L. Thorpe ◽  
Jeffrey M. Young
Keyword(s):  
Wind Speed ◽  
Interannual Variability ◽  
Wind Power ◽  
Tall Tower
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