scholarly journals Air–sea exchange of acetone, acetaldehyde, DMS and isoprene at a UK coastal site

2021 ◽  
Vol 21 (13) ◽  
pp. 10111-10132
Author(s):  
Daniel P. Phillips ◽  
Frances E. Hopkins ◽  
Thomas G. Bell ◽  
Peter S. Liss ◽  
Philip D. Nightingale ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Atmospheric Chemistry ◽  
North Atlantic Ocean ◽  
Open Water ◽  
Gas Transfer ◽  
Gaseous Emissions ◽  
Water Sector ◽  
Transfer Velocity ◽  
Near Surface

Abstract. Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and are important for atmospheric chemistry. Large uncertainties remain in the role of the ocean in the atmospheric VOC budget because of poorly constrained marine sources and sinks. There are very few direct measurements of air–sea VOC fluxes near the coast, where natural marine emissions could influence coastal air quality (i.e. ozone, aerosols) and terrestrial gaseous emissions could be taken up by the coastal seas. To address this, we present air–sea flux measurements of acetone, acetaldehyde and dimethylsulfide (DMS) at the coastal Penlee Point Atmospheric Observatory (PPAO) in the south-west UK during the spring (April–May 2018). Fluxes of these gases were measured simultaneously by eddy covariance (EC) using a proton-transfer-reaction quadrupole mass spectrometer. Comparisons are made between two wind sectors representative of different air–water exchange regimes: the open-water sector facing the North Atlantic Ocean and the terrestrially influenced Plymouth Sound fed by two estuaries. Mean EC (± 1 standard error) fluxes of acetone, acetaldehyde and DMS from the open-water wind sector were −8.0 ± 0.8, −1.6 ± 1.4 and 4.7 ± 0.6 µmol m−2 d−1 respectively (“−” sign indicates net air-to-sea deposition). These measurements are generally comparable (same order of magnitude) to previous measurements in the eastern North Atlantic Ocean at the same latitude. In comparison, the Plymouth Sound wind sector showed respective fluxes of −12.9 ± 1.4, −4.5 ± 1.7 and 1.8 ± 0.8 µmol m−2 d−1. The greater deposition fluxes of acetone and acetaldehyde within the Plymouth Sound were likely to a large degree driven by higher atmospheric concentrations from the terrestrial wind sector. The reduced DMS emission from the Plymouth Sound was caused by a combination of lower wind speed and likely lower dissolved concentrations as a result of the estuarine influence (i.e. dilution). In addition, we measured the near-surface seawater concentrations of acetone, acetaldehyde, DMS and isoprene from a marine station 6 km offshore. Comparisons are made between EC fluxes from the open-water and bulk air–sea VOC fluxes calculated using air and water concentrations with a two-layer (TL) model of gas transfer. The calculated TL fluxes agree with the EC measurements with respect to the directions and magnitudes of fluxes, implying that any recently proposed surface emissions of acetone and acetaldehyde would be within the propagated uncertainty of 2.6 µmol m−2 d−1. The computed transfer velocities of DMS, acetone and acetaldehyde from the EC fluxes and air and water concentrations are largely consistent with previous transfer velocity estimates from the open ocean. This suggests that wind, rather than bottom-driven turbulence and current velocity, is the main driver for gas exchange within the open-water sector at PPAO (depth of ∼ 20 m).

scholarly journals Air-sea exchange of acetone, acetaldehyde, DMS and isoprene at a UK coastal site

2021 ◽  
Author(s):  
Daniel P. Phillips ◽  
Frances E. Hopkins ◽  
Thomas G. Bell ◽  
Peter S. Liss ◽  
Philip D. Nightingale ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Atmospheric Chemistry ◽  
North Atlantic Ocean ◽  
Open Water ◽  
Large Degree ◽  
Gas Transfer ◽  
Gaseous Emissions ◽  
Transfer Velocity ◽  
Near Surface

Abstract. Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and are important for atmospheric chemistry. Large uncertainties remain in the role of the ocean in the atmospheric VOC budget because of poorly constrained marine sources and sinks. There are very few direct measurements of air–sea VOC fluxes near the coast, where natural marine emissions could influence coastal air quality (i.e. ozone, aerosols) and terrestrial gaseous emissions could be taken up by the coastal seas. To address this, we present air–sea flux measurements of acetone, acetaldehyde and dimethylsulfide (DMS) at the coastal Penlee Point Atmospheric Observatory (PPAO) in the South-West UK during the spring (Apr–May 2018). Fluxes of these gases are quantified simultaneously by eddy covariance (EC) using a proton transfer reaction quadrupole mass spectrometer. Comparisons are made between two wind sectors representative of different air–water exchange regimes: the open water sector facing the North Atlantic Ocean and the fetch-limited Plymouth Sound fed by two estuaries. Mean EC (± 1 standard error) fluxes of acetone, acetaldehyde and DMS from the open-water wind sector were −8.0 ± 0.8, −1.6 ± 1.4 and 4.7 ± 0.6 μmol m−2 d−1 respectively (− sign indicates net air-to-sea deposition). These measurements are generally comparable (same order of magnitude) to previous measurements in the Eastern North Atlantic Ocean at the same latitude. In comparison, the terrestrially influenced Plymouth Sound wind sector showed respective fluxes of −12.9 ± 1.4, −4.5 ± 1.7 and 1.8 ± 0.8 μmol m−2 d−1. The greater deposition fluxes of acetone and acetaldehyde within the Plymouth Sound were likely to a large degree driven by higher atmospheric concentrations from the terrestrial wind sector. The reduced DMS emission from the Plymouth Sound was caused by a combination of lower wind speed and likely lower dissolved concentrations as a result of the freshwater estuarine influence (i.e. dilution). In addition, we measured the near surface seawater concentrations of acetone, acetaldehyde, DMS and isoprene from a marine station 6 km offshore. Comparisons are made between EC fluxes from the open water and bulk air–sea VOC fluxes calculated using air/water concentrations with a two-layer (TL) model of gas transfer. The calculated TL fluxes are largely consistent with the EC measurements with respect to the directions and magnitudes of fluxes. Accordingly, the computed transfer velocities of DMS and acetone from the EC fluxes and air/water concentrations are largely consistent with previous transfer velocity estimates from the open ocean.

scholarly journals Air-sea exchange of acetone, acetaldehyde, DMS and isoprene at a UK coastal site.

2021 ◽  
Author(s):  
Daniel Phillips ◽  
Frances Hopkins ◽  
Thomas Bell ◽  
Charel Wohl ◽  
Claire Reeves ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Atmospheric Chemistry ◽  
North Atlantic Ocean ◽  
Open Water ◽  
Proton Transfer Reaction ◽  
Gas Transfer ◽  
Gaseous Emissions ◽  
Near Surface ◽  
Direct Measurements

<p>Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and are important for atmospheric chemistry. Large uncertainties remain in the role of the ocean in the atmospheric VOC budget because of poorly constrained marine sources and sinks. There are very few direct measurements of air-sea VOC fluxes near the coast, where natural marine emissions could influence coastal air quality (i.e. ozone (O<sub>3</sub>), aerosols) and terrestrial gaseous emissions could be taken up by the coastal seas.</p><p>To address this, we present air–sea fluxes of acetone, acetaldehyde and dimethylsulfide (DMS) at the coastal Penlee Point Atmospheric Observatory (PPAO) in the South-West UK during the spring (Apr-May 2018). Fluxes are quantified simultaneously by eddy covariance (EC) using a proton transfer reaction quadrupole mass spectrometer. Comparisons are made between two wind sectors representative of different air-water exchange regimes: the open water sector facing the North Atlantic Ocean and the fetch-limited Plymouth Sound fed by two estuaries.</p><p>Mean EC (± 1 standard error) fluxes of acetone, acetaldehyde and DMS from the open-water wind sector were ‑8.01±0.77, ‑1.55±1.44 and 4.67±0.56 μmol m<sup>-2</sup> d<sup>-1</sup> respectively (- sign indicates air-to-sea deposition). These measurements are generally comparable (same order of magnitude) to previous measurements in the Eastern North Atlantic Ocean at the same latitude. In comparison, the terrestrially influenced Plymouth Sound wind sector showed respective fluxes of -12.93±1.37, -4.45±1.73 and 1.75±0.80 μmol m<sup>-2</sup> d<sup>-1</sup>. The greater deposition fluxes of acetaldehyde and acetone within the Plymouth Sound were largely driven by higher atmospheric concentrations from the terrestrial wind sector. The reduced DMS emission from the Plymouth Sound was caused by a combination of lower wind speed and likely lower dissolved concentrations as a result of the freshwater estuarine influence (i.e. dilution).</p><p>In addition, we measured the near surface seawater concentrations of acetone, acetaldehyde, DMS and isoprene from a marine station 6 km offshore. Comparisons are made between EC fluxes from the open water and diffusive VOC fluxes calculated with a two-layer (TL) model of gas transfer using air/water concentrations. The calculated TL fluxes are largely consistent with our direct measurements in the directions and magnitudes of fluxes. Generally, the TL model predicted acetone and acetaldehyde fluxes that were ~12–33 % higher (greater deposition) than the EC measurements. This could be due to sea surface processes that produce these carbonyl compounds that were not accounted for by the TL technique.</p>

scholarly journals Effect of gas-transfer velocity parameterization choice on air–sea CO<sub>2</sub> fluxes in the North Atlantic Ocean and the European Arctic

Ocean Science ◽  
2016 ◽  
Vol 12 (5) ◽  
pp. 1091-1103 ◽  
Author(s):  
Iwona Wrobel ◽  
Jacek Piskozub
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Global Ocean ◽  
Gas Transfer ◽  
Data Sets ◽  
Transfer Velocity ◽  
The North ◽  
European Arctic ◽  
The North Atlantic

Abstract. The oceanic sink of carbon dioxide (CO2) is an important part of the global carbon budget. Understanding uncertainties in the calculation of this net flux into the ocean is crucial for climate research. One of the sources of the uncertainty within this calculation is the parameterization chosen for the CO2 gas-transfer velocity. We used a recently developed software toolbox, called the FluxEngine (Shutler et al., 2016), to estimate the monthly air–sea CO2 fluxes for the extratropical North Atlantic Ocean, including the European Arctic, and for the global ocean using several published quadratic and cubic wind speed parameterizations of the gas-transfer velocity. The aim of the study is to constrain the uncertainty caused by the choice of parameterization in the North Atlantic Ocean. This region is a large oceanic sink of CO2, and it is also a region characterized by strong winds, especially in winter but with good in situ data coverage. We show that the uncertainty in the parameterization is smaller in the North Atlantic Ocean and the Arctic than in the global ocean. It is as little as 5 % in the North Atlantic and 4 % in the European Arctic, in comparison to 9 % for the global ocean when restricted to parameterizations with quadratic wind dependence. This uncertainty becomes 46, 44, and 65 %, respectively, when all parameterizations are considered. We suggest that this smaller uncertainty (5 and 4 %) is caused by a combination of higher than global average wind speeds in the North Atlantic (> 7 ms−1) and lack of any seasonal changes in the direction of the flux direction within most of the region. We also compare the impact of using two different in situ pCO2 data sets (Takahashi et al. (2009) and Surface Ocean CO2 Atlas (SOCAT) v1.5 and v2.0, for the flux calculation. The annual fluxes using the two data sets differ by 8 % in the North Atlantic and 19 % in the European Arctic. The seasonal fluxes in the Arctic computed from the two data sets disagree with each other possibly due to insufficient spatial and temporal data coverage, especially in winter.

scholarly journals Long-term trends in aerosol and precipitation composition over the western North Atlantic Ocean at Bermuda

2014 ◽  
Vol 14 (5) ◽  
pp. 7025-7066 ◽  
Author(s):  
W. C. Keene ◽  
J. L. Moody ◽  
J. N. Galloway ◽  
J. M. Prospero ◽  
O. R. Cooper ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Flow Regimes ◽  
The United States ◽  
Open Ocean ◽  
Anthropogenic Sources ◽  
Trade Wind ◽  
Chemical Compositions ◽  
Near Surface

Abstract. Since the 1980s, emissions of SO2 and NOx (NO + NO2) from anthropogenic sources in the United States (US) and Europe have decreased significantly suggesting that the export of oxidized S and N compounds from surrounding continents to the atmosphere overlying North Atlantic Ocean (NAO) has also decreased. The chemical compositions of aerosols and precipitation sampled daily on Bermuda (32.27° N, 64.87° W) from 1989 to 1997 and from 2006 to 2009 were evaluated to quantify the magnitudes, significance, and implications of associated tends in atmospheric composition. The chemical data were stratified based on FLEXPART retroplumes into four discrete transport regimes: westerly flow from the eastern North America (NEUS/SEUS); easterly trade-wind flow from northern Africa and the subtropical NAO (Africa); long, open-ocean, anticyclonic flow around the Bermuda High (Oceanic); and transitional flow from the relatively clean open ocean to the polluted northeastern US (North). Based on all data, annual average concentrations of non-sea-salt (nss) SO42- associated with aerosols and annual VWA concentrations in precipitation decreased significantly (by 22 and 49%, respectively) whereas annual VWA concentrations of NH4+ in precipitation increased significantly (by 70%). Corresponding trends in aerosol and precipitation NO3- and of aerosol NH4+ were insignificant. Nss SO42- in precipitation under NEUS/SEUS and Oceanic flow decreased significantly (61% each) whereas corresponding trends in particulate nss SO42- under both flow regimes were insignificant. Trends for precipitation were driven in part by decreasing emissions of SO2 over upwind continents and associated decreases in anthropogenic contributions to nss SO42- concentrations. Under NEUS/SEUS and Oceanic flow, the ratio of anthropogenic to biogenic contributions to to nss SO42- in the column scavenged by precipitation were relatively greater than those in near surface aerosol, which implies that, for these flow regimes, precipitation is a better indicator of overall anthropogenic impacts on the lower troposphere. Particulate nss SO42- under African flow also decreased significantly (34%) whereas the corresponding decrease in nss SO42- associated with precipitation was marginally insignificant. We infer that these trends were driven in part by reductions in the emissions and transport of oxidized S compounds from Europe. The lack of significant trends in NO3- associated with aerosols and precipitation under NEUS/SEUS flow is notable in light of the large decrease (39%) in NOx emissions in the US over the period of record. Rapid chemical processing of oxidized N in marine air contributed to this lack of correspondence. Decreasing ratios of nss SO42- to NH4+ and the significant decreasing trend in precipitation acidity (37%) indicate that the total amount of acidity in the multiphase gas-aerosol system in the western NAO troposphere decreased over the period of record. Decreasing aerosol acidities would have shifted the phase partitioning of total NH3 (NH3 + particulate NH4+) towards the gas phase thereby decreasing the atmospheric lifetime of total NH3 against wet plus dry deposition. The trend of increasing NH4+ in precipitation at Bermuda over the period of record suggests that NH3 emissions from surrounding continents also increased. Decreasing particulate nss SO42- in near-surface air under NEUS/SEUS flow over the period of record suggests a lower limit for net warming in the range of 0.1–0.3 W m-2 resulting from the decreased shortwave scattering and absorption by nss SO42- and associated aerosol constituents.

scholarly journals Effect of a Variable Eddy Transfer Coefficient in an Eddy-Permitting Model of the Subpolar North Atlantic Ocean

2005 ◽  
Vol 35 (3) ◽  
pp. 289-307 ◽  
Author(s):  
Daniel Deacu ◽  
Paul G. Myers
Keyword(s):  
Atlantic Ocean ◽  
Transfer Coefficient ◽  
North Atlantic ◽  
General Circulation ◽  
North Atlantic Ocean ◽  
Negative Impact ◽  
Labrador Sea ◽  
Western Boundary ◽  
Near Surface ◽  
Eastern North Atlantic

Abstract The effect of using a variable eddy transfer coefficient for the Gent–McWilliams (GM) parameterization in a (1/3)°-resolution ocean model of the subpolar North Atlantic Ocean is investigated. Results from four experiments with different implementations of this coefficient are compared among themselves as well as with two control experiments. A series of improvements have been obtained in all of the experiments that use a low level of explicit horizontal tracer diffusion. These include a better representation of the overflow waters originating from the Nordic seas, leading to a more realistic deep western boundary current and to increased eddy activity in the deep ocean in the eastern North Atlantic. In the same experiments, the GM velocities “help” the Labrador Sea Water to spread from the deep convection region to the currents that surround it without incurring significant spurious diapycnal mixing. Thus, two classical pathways for the spreading of this water are established. Moreover, the simulated Labrador Current and the near-surface circulation in the eastern North Atlantic are in better agreement with flow patterns inferred from observations. The increased release of available potential energy obtained in the experiments with variable eddy transfer coefficients is responsible for the simulation of a flow that varies less in time. An overly strong countercurrent still occurs in the Labrador Sea in these experiments, and it has a negative impact on the pathway of the North Atlantic Current in the “Northwest Corner” and on the hydrography of the Labrador Sea. Nonetheless and overall, the use of the variable eddy transfer coefficient has led to better representations of the general circulation and hydrography in the subpolar North Atlantic.

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.

TOSST Research Expeditions in the North Atlantic Ocean

2020 ◽  
Author(s):  
Ricardo Arruda ◽  
Lorenza Raimondi ◽  
Patrick Duplessis ◽  
Nadine Lehmann ◽  
Irena Schulten ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Atmospheric Chemistry ◽  
Personal Development ◽  
North Atlantic Ocean ◽  
Early Career ◽  
The Arctic ◽  
The North ◽  
Research Institutes ◽  
The North Atlantic

&lt;p&gt;&lt;span&gt;Over the 6 years of the Transatlantic Ocean System Science and Technology program (TOSST - 2014 &amp;#8211; 2019), graduate students participated in a variety of first class research expeditions in the North Atlantic Ocean, contributing to high quality datasets for this region and reaching a total of 380 days at-sea. These research cruises expanded from the Arctic Ocean, Labrador Sea and sub-Polar North Atlantic to the Equatorial North Atlantic, and along the African and Cabo Verdean coasts. A total of 12 long term cruises with collaboration between 18 research institutes, were conducted on board of 10 research vessels of various nationalities (Canada, Germany, Bermuda, Sweden, Ireland and USA). The range of measurements performed during these cruises, which highlights the interdisciplinary nature of the TOSST program, includes: chemical oceanography; biological oceanography; physical oceanography; marine biogeochemistry; microbiology; paleoceanography; geology; marine geophysics; and atmospheric chemistry. In this work, we will showcase the breath of research covered by TOSST graduates in the North Atlantic Ocean and provide details on the overall goals/objectives of each cruise, the teams and research vessels involved, the diverse scientific instrumentation deployed and sampling schemes. We highlight the importance of multi-disciplinary expeditions and at-sea experiences for professional as well as for personal development of early career scientists. Logistic and economic efforts are required to collect samples and to deploy instruments, therefore collaboration between disciplines, research institutes and countries (of which TOSST graduates&amp;#8217; research is an example) are fundamental in order to increase the quality, quantity and variety of observations in the North Atlantic Ocean. &lt;/span&gt;&lt;/p&gt;

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