New parameterizations of air-sea CO2 gas transfer velocity on wave breaking

2021 ◽  
Author(s):  
Shuo Li ◽  
Alexander Babanin
Keyword(s):  
Wind Speed ◽  
Wave Breaking ◽  
Global Ocean ◽  
Gas Transfer ◽  
Data Sets ◽  
Orbital Velocity ◽  
Transfer Velocity ◽  
Gas Transfer Velocity ◽  
Wave Parameters ◽  
Transfer Models

<p>Ocean surface waves and wave breaking play a pivotal role in air-sea Carbon Dioxide (<em>CO<sub>2</sub></em>) gas exchange by producing abundant turbulence and bubbles. Contemporary gas transfer models are generally implemented with wind speed, rather than wave parameters, to quantify <em>CO<sub>2</sub></em> transfer velocity (<em>K<sub>CO2</sub></em>). In our work, the direct relationship of <em>K<sub>CO2</sub></em> and waves is explored through the combination of laboratory experiment, field observational data and estimation of global ocean uptake of <em>CO<sub>2</sub></em>.</p><p>In laboratory, the waves and <em>CO<sub>2 </sub></em>transfer at water surface are forced for simultaneous measurements in a wind-wave flume. Three types of waves are exercised: mechanically generated monochromatic waves, pure wind waves with 10-meter wind speed ranging from 4.5 <em>m/s</em> to 15.5 <em>m/s</em>, and the coupling of monochromatic waves with superimposed wind force. The results show that <em>K<sub>CO2 </sub></em>is well correlated with wave height and orbital velocity. In the connection of <em>K<sub>CO2 </sub></em>with breakers, wave breaking probability (<em>b<sub>T</sub></em>) should also be considered. The wind speed is competent too in describing <em>K<sub>CO2 </sub></em>but may be inadequate for varied wave ages. A non-dimensional formula (hereafter the RHM model) is proposed in which gas transfer velocity is expressed as a main function of wave Reynolds number (<em>R<sub>HM </sub>= U<sub>w</sub>H<sub>s</sub>/ν<sub>w</sub></em>, where <em>U<sub>w</sub></em> is wave orbital velocity, <em>H<sub>s</sub></em> is significant wave height, <em>ν<sub>w</sub></em> is viscosity of water) while wind is accounted as an enhancement factor (<em>1+Û</em>, where <em>Û </em>is non-dimensional wind speed denoting the reverse of wave age). For wave breaking dominated gas exchange, second formula (hereafter the BT model) is developed by replacing components of <em>R<sub>HM </sub></em>with breaker’s statistics and integrates an additional factor of <em>b<sub>T. </sub></em></p><p>Utilizing campaign observations from open ocean, the RHM model can effectively reconcile the laboratory and field data sets. The BT model related with wave breaking, on the other hand, is adapted by including a complementary term of bubble-mediated gas transfer in which the bubble injection rate is parameterized with <em>R<sub>HM</sub></em>. The updated BT model also performs well for the data. The conventional wind-based models show similar features as in laboratory experiments: the wind speed successfully captures the variation of gas transfer for respective observation yet is insufficient to neutralize the gaps among data sets.</p><p>Our wave-based gas transfer models are applied for the estimation of net annual <em>CO<sub>2</sub></em> fluxes of global ocean in the period of year 1985-2017. The results are in high agreement with previous studies. The wind-based gas transfer models might underestimate the <em>CO<sub>2</sub></em> fluxes although the estimations still distribute within the range of uncertainty. Moreover, the models using wave parameters are found advantageous over the wind-based models in reducing the uncertainties of gas fluxes.</p>

scholarly journals The influence of transformed Reynolds number limitation on gas transfer parameterizations and global DMS and CO<sub>2</sub> fluxes

2018 ◽  
Author(s):  
Alexander Zavarsky ◽  
Christa A. Marandino
Keyword(s):  
Reynolds Number ◽  
Wind Speed ◽  
Wind Wave ◽  
Wave Interaction ◽  
Gas Transfer ◽  
Data Sets ◽  
High Wind Speed ◽  
Transfer Velocity ◽  
Gas Transfer Velocity ◽  
Eddy Covariance Measurements

Abstract. Eddy covariance measurements show gas transfer velocity limitation at medium to high wind speed. A wind-wave interaction described by the transformed Reynolds number is used to characterize environmental conditions favoring this limitation. We take the transformed Reynolds number parameterization to review the two most cited wind speed gas transfer velocity parameterizations, Nightingale 2000 and Wanninkhof 1992/2014. We propose an algorithm to correct for the effect of gas transfer limitation and validate it with two gas transfer limited directly measured DMS gas transfer velocity data sets. A correction of the Nightingale 2000 parameterization leads to an average increase of 22 % of its predicted gas transfer velocity. The increase for Wanninkhof 2014 is 9.85 %. Additionally, the correction is applied to global air-sea flux climatologies of CO2 and DMS. The global application of gas transfer limitation leads to a decrease of 6–7 % for the uptake CO2 by the oceans and to decrease of 11 % of oceanic outgassing of DMS. We expect the magnitude of Reynolds limitation on any global air-sea gas exchange to be 10 %.

scholarly journals The influence of transformed Reynolds number suppression on gas transfer parameterizations and global DMS and CO<sub>2</sub> fluxes

2019 ◽  
Vol 19 (3) ◽  
pp. 1819-1834 ◽  
Author(s):  
Alexander Zavarsky ◽  
Christa A. Marandino
Keyword(s):  
Reynolds Number ◽  
Wind Speed ◽  
Dimethyl Sulfide ◽  
Wave Interaction ◽  
Gas Transfer ◽  
Data Sets ◽  
Transfer Velocity ◽  
Data Set ◽  
Suppression Effect ◽  
Gas Transfer Velocity

Abstract. Eddy covariance measurements show gas transfer velocity suppression at medium to high wind speed. A wind–wave interaction described by the transformed Reynolds number is used to characterize environmental conditions favoring this suppression. We take the transformed Reynolds number parameterization to review the two most cited wind speed gas transfer velocity parameterizations: Nightingale et al. (2000) and Wanninkhof (1992, 2014). We propose an algorithm to adjust k values for the effect of gas transfer suppression and validate it with two directly measured dimethyl sulfide (DMS) gas transfer velocity data sets that experienced gas transfer suppression. We also show that the data set used in the Nightingale 2000 parameterization experienced gas transfer suppression. A compensation of the suppression effect leads to an average increase of 22 % in the k vs. u relationship. Performing the same correction for Wanninkhof 2014 leads to an increase of 9.85 %. Additionally, we applied our gas transfer suppression algorithm to global air–sea flux climatologies of CO2 and DMS. The global application of gas transfer suppression leads to a decrease of 11 % in DMS outgassing. We expect the magnitude of Reynolds suppression on any global air–sea gas exchange to be about 10 %.

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

Geosciences ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 230
Author(s):  
Mariana Ribas-Ribas ◽  
Gianna Battaglia ◽  
Matthew P. Humphreys ◽  
Oliver Wurl
Keyword(s):  
Wind Speed ◽  
Ocean Model ◽  
Global Ocean ◽  
Gas Transfer ◽  
Co2 Fluxes ◽  
Average Wind Speed ◽  
Transfer Velocity ◽  
Gas Transfer Velocity ◽  
Wind Speeds

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.

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;

The gas transfer velocity —wind speed relationship at Siblyback Lake: A reply to comments by Kwan and Taylor

Tellus B ◽  
1993 ◽  
Vol 45 (3) ◽  
pp. 299-300 ◽  
Author(s):  
Robert C. Upstill-Goddard ◽  
Andrew J. Watson ◽  
Peter S. Liss
Keyword(s):  
Wind Speed ◽  
Gas Transfer ◽  
Transfer Velocity ◽  
Gas Transfer Velocity

scholarly journals DMS gas transfer coefficients from algal blooms in the Southern Ocean

2014 ◽  
Vol 14 (21) ◽  
pp. 28453-28482
Author(s):  
T. G. Bell ◽  
W. De Bruyn ◽  
C. A. Marandino ◽  
S. D. Miller ◽  
C. S. Law ◽  
...  
Keyword(s):  
Wind Speed ◽  
Southern Ocean ◽  
Eddy Covariance ◽  
Algal Blooms ◽  
Biologically Active ◽  
Gas Transfer ◽  
Transfer Coefficients ◽  
Transfer Velocity ◽  
Gas Transfer Velocity ◽  
Wind Speeds

Abstract. Air/sea dimethylsulfide (DMS) fluxes and bulk air/sea gradients were measured over the Southern Ocean in February/March 2012 during the Surface Ocean Aerosol Production (SOAP) study. The cruise encountered three distinct phytoplankton bloom regions, consisting of two blooms with moderate DMS levels, and a high biomass, dinoflagellate-dominated bloom with high seawater DMS levels (>15 nM). Gas transfer coefficients were considerably scattered at wind speeds above 5 m s−1. Bin averaging the data resulted in a linear relationship between wind speed and mean gas transfer velocity consistent with that previously observed. However, the wind speed-binned gas transfer data distribution at all wind speeds is positively skewed. The flux and seawater DMS distributions were also positively skewed, which suggests that eddy covariance-derived gas transfer velocities are consistently influenced by additional, log-normal noise. A~flux footprint analysis was conducted during a transect into the prevailing wind and through elevated DMS levels in the dinoflagellate bloom. Accounting for the temporal/spatial separation between flux and seawater concentration significantly reduces the scatter in computed transfer velocity. The SOAP gas transfer velocity data shows no obvious modification of the gas transfer-wind speed relationship by biological activity or waves. This study highlights the challenges associated with eddy covariance gas transfer measurements in biologically active and heterogeneous bloom environments.

scholarly journals Net sea-air CO<sub>2</sub> flux uncertainties in the Bay of Biscay based on the choice of wind speed products and gas transfer parameterizations

2012 ◽  
Vol 9 (8) ◽  
pp. 9993-10017
Author(s):  
P. Otero ◽  
X. A. Padín ◽  
M. Ruiz-Villarreal ◽  
L. M. García-García ◽  
A. F. Ríos ◽  
...  
Keyword(s):  
Wind Speed ◽  
Co2 Flux ◽  
Forecast Model ◽  
Gas Transfer ◽  
Co2 Uptake ◽  
Bay Of Biscay ◽  
Transfer Velocity ◽  
Gas Transfer Velocity ◽  
Different Sources ◽  
Meteorological Models

Abstract. The estimation of sea-air CO2 fluxes are largely dependent on wind speed through the gas transfer velocity parameterization. In this paper, we quantify uncertainties in the estimation of the CO2 uptake in the Bay of Biscay resulting from using different sources of wind speed such as three different global reanalysis meteorological models (NCEP/NCAR 1, NCEP/DOE 2 and ERA-Interim), one regional high-resolution forecast model (HIRLAM-AEMet) and QuikSCAT winds, in combination with some of the most widely used gas transfer velocity parameterizations. Results show that net CO2 flux estimations during an entire seasonal cycle may differ up to 240% depending on the wind speed product and the gas exchange parameterization. The comparison of satellite and model derived winds with observations at buoys advises against the systematic overestimation of NCEP-2 and the underestimation of NCEP-1. In this region, QuikSCAT has the best performing, although ERA-Interim becomes the best choice in areas near the coastline or when the time resolution is the constraint.

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.

scholarly journals Insights from year-long measurements of air–water CH<sub>4</sub> and CO<sub>2</sub> exchange in a coastal environment

2019 ◽  
Vol 16 (5) ◽  
pp. 961-978 ◽  
Author(s):  
Mingxi Yang ◽  
Thomas G. Bell ◽  
Ian J. Brown ◽  
James R. Fishwick ◽  
Vassilis Kitidis ◽  
...  
Keyword(s):  
Wind Speed ◽  
Co2 Flux ◽  
Open Water ◽  
Gas Transfer ◽  
Co2 Efflux ◽  
Water Sector ◽  
Transfer Velocity ◽  
Ch4 Flux ◽  
Gas Transfer Velocity

Abstract. Air–water CH4 and CO2 fluxes were directly measured using the eddy covariance technique at the Penlee Point Atmospheric Observatory on the southwest coast of the United Kingdom from September 2015 to August 2016. The high-frequency, year-long measurements provide unprecedented detail on the variability of these greenhouse gas fluxes from seasonal to diurnal and to semi-diurnal (tidal) timescales. Depending on the wind sector, fluxes measured at this site are indicative of air–water exchange in coastal seas as well as in an outer estuary. For the open-water sector when winds were off the Atlantic Ocean, CH4 flux was almost always positive (annual mean of ∼0.05 mmol m−2 d−1) except in December and January, when CH4 flux was near zero. At times of high rainfall and river flow rate, CH4 emission from the estuarine-influenced Plymouth Sound sector was several times higher than emission from the open-water sector. The implied CH4 saturation (derived from the measured fluxes and a wind-speed-dependent gas transfer velocity parameterization) of over 1000 % in the Plymouth Sound is within range of in situ dissolved CH4 measurements near the mouth of the river Tamar. CO2 flux from the open-water sector was generally from sea to air in autumn and winter and from air to sea in late spring and summer, with an annual mean flux of near zero. A diurnal signal in CO2 flux and implied partial pressure of CO2 in water (pCO2) are clearly observed for the Plymouth Sound sector and also evident for the open-water sector during biologically productive periods. These observations suggest that coastal CO2 efflux may be underestimated if sampling strategies are limited to daytime only. Combining the flux data with seawater pCO2 measurements made in situ within the flux footprint allows us to estimate the CO2 transfer velocity. The gas transfer velocity and wind speed relationship at this coastal location agrees reasonably well with previous open-water parameterizations in the mean but demonstrates considerable variability. We discuss the influences of biological productivity, bottom-driven turbulence and rainfall on coastal air–water gas exchange.

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