scholarly journals Variability of air-sea gas transfer velocities in the Baltic Sea

2018 ◽  
Author(s):  
Leila Nagel ◽  
Kerstin E. Krall ◽  
Bernd Jähne
Keyword(s):  
Heat Transfer ◽  
Wind Speed ◽  
Baltic Sea ◽  
Active Material ◽  
Gas Transfer ◽  
The Baltic Sea ◽  
Transfer Velocity ◽  
Wind Speeds ◽  
The Baltic ◽  
Surface Active Material

Abstract. Heat transfer velocities measured during three different campaigns in the Baltic Sea using the Active Controlled Flux Technique (ACFT) with wind speeds ranging from 5.3 to 14.8 m s−1 are presented. Careful scaling of the heat transfer velocities to gas transfer velocities using Schmidt number exponents measured in a laboratory study allows to compare the measured transfer velocities to existing gas transfer velocity parameterizations, which use wind speed as the controlling parameter. The measured data and other field data clearly show that some gas transfer velocities are much lower than the empirical wind speed parametrizations. This indicates that the dependencies of the transfer velocity on the fetch, i.e., the history of the wind and the age of the wind wave field, and the effects of surface active material need to be taken into account.

scholarly journals Measurements of air–sea gas transfer velocities in the Baltic Sea

Ocean Science ◽  
2019 ◽  
Vol 15 (2) ◽  
pp. 235-247 ◽  
Author(s):  
Leila Nagel ◽  
Kerstin E. Krall ◽  
Bernd Jähne
Keyword(s):  
Heat Transfer ◽  
Wind Speed ◽  
Baltic Sea ◽  
Active Material ◽  
Gas Transfer ◽  
The Baltic Sea ◽  
Transfer Velocity ◽  
Wind Speeds ◽  
The Baltic ◽  
Surface Active Material

Abstract. Heat transfer velocities measured during three different campaigns in the Baltic Sea using the active controlled flux technique (ACFT) with wind speeds ranging from 5.3 to 14.8 m s−1 are presented. Careful scaling of the heat transfer velocities to gas transfer velocities using Schmidt number exponents measured in a laboratory study allows us to compare the measured transfer velocities to existing gas transfer velocity parameterizations, which use wind speed as the controlling parameter. The measured data and other field data clearly show that some gas transfer velocities are much lower than those based on the empirical wind speed parameterizations. This indicates that the dependencies of the transfer velocity on the fetch, i. e., the history of the wind and the age of the wind-wave field, and the effects of surface-active material need to be taken into account.

scholarly journals Air–sea CO2 exchange in the Baltic Sea—A sensitivity analysis of the gas transfer velocity

2021 ◽  
pp. 103603
Author(s):  
Lucía Gutiérrez-Loza ◽  
Marcus B. Wallin ◽  
Erik Sahlée ◽  
Thomas Holding ◽  
Jamie D. Shutler ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Baltic Sea ◽  
Co2 Exchange ◽  
Gas Transfer ◽  
The Baltic Sea ◽  
Transfer Velocity ◽  
Gas Transfer Velocity ◽  
The Baltic

Determination of gaseous elemental mercury air-sea exchange in the Baltic Sea

2020 ◽  
Author(s):  
Stefan Osterwalder ◽  
Michelle Nerentorp ◽  
Wei Zhu ◽  
Erik Nilsson ◽  
Mats Nilsson ◽  
...  
Keyword(s):  
Wind Speed ◽  
Baltic Sea ◽  
Elemental Mercury ◽  
The Baltic Sea ◽  
Transfer Velocity ◽  
Field Station ◽  
Gaseous Elemental Mercury ◽  
Starting Point ◽  
Flux Measurements ◽  
The Baltic

<p>Ocean waters store approximately 400 Gg of mercury (Hg) and exchange it with the atmosphere at a high rate. Air-sea exchange of gaseous elemental mercury (Hg<sup>0</sup>) is a key process in global Hg cycling because evasion lowers the reservoir of Hg(II) available for methylation and subsequent bioaccumulation in marine fish and prolongs the atmospheric lifetime and subsequently global cycling of Hg. However, global estimates on the air-sea flux are not well constrained (1.9 to 4.2 Gg a<sup>-1</sup>) mainly because high-resolution measurements of Hg<sup>0</sup> in seawater are largely lacking and parameterization of the Hg<sup>0</sup> transfer velocity introduces uncertainties in Hg<sup>0</sup> flux modelling. We present estimates of the net Hg<sup>0</sup> flux for the Baltic Sea derived from land-based marine measurements of Hg<sup>0</sup> in air and seawater as well as micrometeorological techniques. We found that coastal waters at the ICOS field station Östergarnsholm, located east of Gotland, Sweden, were typically supersaturated with seawater Hg<sup>0</sup> (mean ± SD = 13.5 ± 3.5 ng m<sup>-3</sup>; ca. 10 % of total Hg) compared to ambient Hg<sup>0</sup> (1.3 ± 0.2 ng m<sup>-3</sup>). The Hg<sup>0</sup> flux calculated using gas-transfer wind speed relationships ranged from 0.1 to 1.3 ng m<sup>-2</sup> h<sup>-1</sup> over the course of the campaign (May 10 – June 20, 2017). The modeled Hg<sup>0</sup> flux showed a distinct diel pattern with an average daytime flux of 0.6 ng m<sup>-2</sup> h<sup>-1</sup> and nighttime flux of 0.4 ng m<sup>-2</sup> h<sup>-1</sup>, indicating that temperature and light induced production of seawater Hg<sup>0</sup> was of significance in shallow waters. Preliminary calculations of the average coastal Hg<sup>0</sup> flux simultaneously measured using direct, non-intrusive gradient-based, aerodynamic gradient and relaxed eddy accumulation techniques were 0.5 ± 1, 0.6 ± 3.8 and 0.6 ± 37 ng m<sup>-2</sup> h<sup>-1</sup>, respectively. Although, these flux estimates were in good agreement, there were indications in the temporal patters of the observations, which suggest that there is a need to reconsider the modeled flux with the support of more direct flux measurements. Direct flux measurements revealed not only Hg<sup>0</sup> evasion but also periods of Hg<sup>0</sup> dry deposition. In addition, direct measurements indicated a stronger wind speed dependence of the Hg<sup>0</sup> transfer velocity compared to CO<sub>2</sub> which appears to coincide with whitecap formation in the open sea flux footprint (wind speed > 5 m s<sup>-1</sup>). Hence, we anticipate this study as a starting point for more land-based, marine, continuous measurements of seawater Hg<sup>0</sup> concentration in combination with micrometeorological fluxes in order to improve Hg<sup>0</sup> flux estimates in regional and global scale models. In this context, directly measured Hg<sup>0</sup> fluxes will be pivotal to improve transfer velocity estimates of Hg<sup>0</sup> especially during periods of high wind speed.</p>

scholarly journals Assessment of Wind Shear and Wind Energy Potential in the Baltic Sea Region of Latvia

2015 ◽  
Vol 52 (2) ◽  
pp. 26-39
Author(s):  
V. Bezrukovs ◽  
Vl. Bezrukovs ◽  
A. Zacepins ◽  
V. Komashilovs
Keyword(s):  
Wind Speed ◽  
Wind Energy ◽  
Baltic Sea ◽  
Density Fluctuations ◽  
Western Coast ◽  
The Baltic Sea ◽  
Energy Potential ◽  
North East ◽  
Wind Energy Potential ◽  
The Baltic

Abstract The paper is devoted to the investigation into the wind energy potential based on long-term observations of the wind speed and energy density fluctuations at heights from 10 to 160 m on the Baltic Sea coast of Latvia. During the observations (2004 - 2013), the wind speed and direction values were measured, and the statistical database was accumulated using a LOGGER 9200 Symphonie measuring systems mounted on 60 m masts - one on the western coast and another on the north-east of Latvia. From June 2011 to May 2012, these measurements were complemented with the data for the heights from 40 to 160 m obtained by means of a ZephIR lidar and with the metrological data provided by “Latvian Environment, Geology and Meteorology Centre” for the same period. The graphs of seasonal fluctuations in the wind speed were obtained for the heights up to 160 m by measurements over the period of 2007 - 2013. The results of the research on the wind speed distribution up to 200 m are promising for evaluation of the wind energy potential of Latvia and will be helpful in assessment of prospective sites for construction of WPPs.

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 Sensitivity of the air–sea CO<sub>2</sub> exchange in the Baltic Sea and Danish inner waters to atmospheric short term variability

2014 ◽  
Vol 11 (12) ◽  
pp. 16993-17042
Author(s):  
A. S. Lansø ◽  
J. Bendtsen ◽  
J. H. Christensen ◽  
L. L. Sørensen ◽  
H. Chen ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Co2 Flux ◽  
Co2 Concentration ◽  
Co2 Exchange ◽  
Atmospheric Co2 ◽  
The Baltic Sea ◽  
Short Term ◽  
Transfer Velocity ◽  
The Baltic ◽  
Short Term Variability

Abstract. Minimising the uncertainties in estimates of air–sea CO2 exchange is an important step toward increasing the confidence in assessments of the CO2 cycle. Using an atmospheric transport model makes it possible to investigate the direct impact of atmospheric parameters on the air–sea CO2 flux along with its sensitivity to e.g. short-term temporal variability in wind speed, atmospheric mixing height and the atmospheric CO2 concentration. With this study the importance of high spatiotemporal resolution of atmospheric parameters for the air–sea CO2 flux is assessed for six sub-basins within the Baltic Sea and Danish inner waters. A new climatology of surface water partial pressure of CO2 (pCO2) has been developed for this coastal area based on available data from monitoring stations and underway pCO2 measuring systems. Parameterisations depending on wind speed were applied for the transfer velocity to calculate the air–sea CO2 flux. Two model simulations were conducted – one including short term variability in atmospheric CO2 (VAT), and one where it was not included (CAT). A seasonal cycle in the air–sea CO2 flux was found for both simulations for all sub-basins with uptake of CO2 in summer and release of CO2 to the atmosphere in winter. During the simulated period 2005–2010 the average annual net uptake of atmospheric CO2 for the Baltic Sea, Danish Straits and Kattegat was 287 and 471 Gg C yr-1 for the VAT and CAT simulations, respectively. The obtained difference of 184 Gg C yr-1 was found to be significant, and thus ignoring short term variability in atmospheric CO2 does have a sizeable effect on the air–sea CO2 exchange. The combination of the atmospheric model and the new pCO2 fields has also made it possible to make an estimate of the marine part of the Danish CO2 budget for the first time. A net annual uptake of 2613 Gg C yr-1 was found for the Danish waters. A large uncertainty is connected to the air–sea CO2 flux in particular caused by the transfer velocity parameterisation and the applied pCO2 climatology. However, the present study underlines the importance of including short term variability in the atmospheric CO2 concentration in future model studies of the air–sea exchange in order to minimise the uncertainty.

scholarly journals Natural variability in air–sea gas transfer efficiency of CO2

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mingxi Yang ◽  
Timothy J. Smyth ◽  
Vassilis Kitidis ◽  
Ian J. Brown ◽  
Charel Wohl ◽  
...  
Keyword(s):  
Wind Speed ◽  
Transfer Efficiency ◽  
Gas Transfer ◽  
Transfer Velocity ◽  
Concentration Difference ◽  
Near Surface ◽  
Wind Speeds ◽  
Naturally Occurring ◽  
Surface Active ◽  
The Mean

AbstractThe flux of CO2 between the atmosphere and the ocean is often estimated as the air–sea gas concentration difference multiplied by the gas transfer velocity (K660). The first order driver for K660 over the ocean is wind through its influence on near surface hydrodynamics. However, field observations have shown substantial variability in the wind speed dependencies of K660. In this study we measured K660 with the eddy covariance technique during a ~ 11,000 km long Southern Ocean transect. In parallel, we made a novel measurement of the gas transfer efficiency (GTE) based on partial equilibration of CO2 using a Segmented Flow Coil Equilibrator system. GTE varied by 20% during the transect, was distinct in different water masses, and related to K660. At a moderate wind speed of 7 m s−1, K660 associated with high GTE exceeded K660 with low GTE by 30% in the mean. The sensitivity of K660 towards GTE was stronger at lower wind speeds and weaker at higher wind speeds. Naturally-occurring organics in seawater, some of which are surface active, may be the cause of the variability in GTE and in K660. Neglecting these variations could result in biases in the computed air–sea CO2 fluxes.

scholarly journals First Application of IFCB High-Frequency Imaging-in-Flow Cytometry to Investigate Bloom-Forming Filamentous Cyanobacteria in the Baltic Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Kaisa Kraft ◽  
Jukka Seppälä ◽  
Heidi Hällfors ◽  
Sanna Suikkanen ◽  
Pasi Ylöstalo ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Wind Speed ◽  
Baltic Sea ◽  
Water Temperature ◽  
High Frequency ◽  
Filamentous Cyanobacteria ◽  
Monitoring Methods ◽  
The Baltic Sea ◽  
Imaging Flow Cytometry ◽  
The Baltic

Cyanobacteria are an important part of phytoplankton communities, however, they are also known for forming massive blooms with potentially deleterious effects on recreational use, human and animal health, and ecosystem functioning. Emerging high-frequency imaging flow cytometry applications, such as Imaging FlowCytobot (IFCB), are crucial in furthering our understanding of the factors driving bloom dynamics, since these applications provide community composition information at frequencies impossible to attain using conventional monitoring methods. However, the proof of applicability of automated imaging applications for studying dynamics of filamentous cyanobacteria is still scarce. In this study we present the first results of IFCB applied to a Baltic Sea cyanobacterial bloom community using a continuous flow-through setup. Our main aim was to demonstrate the pros and cons of the IFCB in identifying filamentous cyanobacterial taxa and in estimating their biomass. Selected environmental parameters (water temperature, wind speed and salinity) were included, in order to demonstrate the dynamics of the system the cyanobacteria occur in and the possibilities for analyzing high-frequency phytoplankton observations against changes in the environment. In order to compare the IFCB results with conventional monitoring methods, filamentous cyanobacteria were enumerated from water samples using light microscopical analysis. Two common bloom forming filamentous cyanobacteria in the Baltic Sea, Aphanizomenon flosaquae and Dolichospermum spp. dominated the bloom, followed by an increase in Oscillatoriales abundance. The IFCB results compared well with the results of the light microscopical analysis, especially in the case of Dolichospermum. Aphanizomenon biomass varied slightly between the methods and the Oscillatoriales results deviated the most. Bloom formation was initiated as water temperature increased to over 15°C and terminated as the wind speed increased, dispersing the bloom. Community shifts were closely related to movements of the water mass. We demonstrate how using a high-frequency imaging flow cytometry application can help understand the development of cyanobacteria summer blooms.

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