Distribution and sea‐air fluxes of biogenic trace gases in the eastern Atlantic Ocean

Baker, Alex R.; Turner, Suzanne M.; Broadgate, Wendy; Thompson, A.; McFiggans, G.; Vesperini, O.; Nightingale, Philip D.; Liss, Peter S.; Jickells, TD

doi:10.1029/1999gb001219

Cited by 101 publications

(83 citation statements)

References 67 publications

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“…This is probably because sea-to-air fluxes of methyl iodide are more heavily influenced by changes in wind speed than seawater concentration [Baker et al, 2000b], so high surface water concentrations are offset by lower mean wind speeds in summertime, while in wintertime, high wind speeds promote transfer to the atmosphere.…”

Section: Resultsmentioning

confidence: 98%

Iodine speciation and deposition fluxes from the marine atmosphere

Baker¹,

Tunnicliffe²,

Jickells³

2001

J. Geophys. Res.

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Abstract. The concentration and speciation of iodine have been determined in wet and dry •)deposition at a coastal site over a 15-month period. Deposition fluxes in rain (2.7 txmol m -2 yrand aerosol (3.6-6.5 txmol m -2 yr -•) are the major routes for removal of iodine from the marine atmosphere onto the Earth's surface, with only a minor contribution from direct deposition of methyl iodide (0.003-0.17 txmol m -• yr-•). Iodate (IO•-) is often considered to be the only species of iodine that is permanently removed to the aerosol phase, and IO• may therefore be expected to be the dominant form of iodine in precipitation. However, iodide (I-) was found to constitute a significant fraction (5-100%) of iodine in both rain and aerosol. This implies that the rates of iodate formation and iodide volatilization (through reaction with hypohalous acids) are relatively slow. A third pool of aerosol iodine (nonvolatile organic compounds) may also contribute to removal of iodine from the atmosphere in dry or wet deposition. In this work we present the results of a long-term study of iodine deposition at a coastal site in southeast England. We have determined iodine concentrations in rain and aerosol samples and used these to calculate wet and dry deposition fluxes of iodine to the ground at the site. In addition, we also use gas-phase concentrations of methyl iodide, the longest-lived iodocarbon, to calculate the potential contribution to dry deposition of direct gas-to-land transfen This work follows on from the study of Campos et al. [1996], who reported that the annual emission budget of methyl iodide was in near balance with the deposition budget of iodine in rainfall in the southern North Sea region. The current data set is used to extend the iodine deposition budget, by inclusion of dry deposition, which was neglected in the earlier work. In addition, by examining the speciation of iodine in aerosol and rain we consider the influence of meteorology on the atmospheric processing of iodine in aerosol.

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Section: Resultsmentioning

confidence: 98%

Iodine speciation and deposition fluxes from the marine atmosphere

Baker¹,

Tunnicliffe²,

Jickells³

2001

J. Geophys. Res.

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“…Our flux estimates for this region and month range from 0.04×10 8 to 1.7×10 8 molecules cm −2 s −1 for the 0.31 and 1.9 Tg/yr sources, with mean values of 0.07×10 8 and 0.42×10 8 molecules cm −2 s −1 , respectively, again demonstrating good agreement with the observations. In the North Atlantic Ocean, there is evidence that our estimated fluxes (0.25×10 8 -1.5×10 8 molecules cm −2 s −1 ) are large compared with observed fluxes of 0.08×10 8 to 0.6×10 8 molecules cm −2 s −1 during May 1997 (Baker et al, 2000).…”

Section: Evaluation Of Marine Isoprene Emissionsmentioning

confidence: 92%

Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol

et al. 2009

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Abstract. We have combined the first satellite maps of the global distribution of phytoplankton functional type and new measurements of phytoplankton-specific isoprene productivities, with available remote marine isoprene observations and a global model, to evaluate our understanding of the marine isoprene source and its impacts on organic aerosol abundances. Using satellite products to scale up data on phytoplankton-specific isoprene productivity to the global oceans, we infer a mean "bottom-up" oceanic isoprene emission of 0.31±0.08 (1σ )Tg/yr. By minimising the mean bias between the model and isoprene observations in the marine atmosphere remote from the continents, we produce a "topdown" oceanic isoprene source estimate of 1.9 Tg/yr. We suggest our reliance on limited atmospheric isoprene data, difficulties in simulating in-situ isoprene production rates in laboratory phytoplankton cultures, and limited knowledge of isoprene production mechanisms across the broad range of phytoplankton communities in the oceans under different environmental conditions as contributors to this difference between the two estimates. Inclusion of secondary organic aerosol (SOA) production from oceanic isoprene in the model with a 2% yield produces small contributions (0.01-1.4%) to observed organic carbon (OC) aerosol mass at three remote marine sites in the Northern and Southern Hemispheres. Based on these findings we suggest an insignificant role for isoprene in modulating remote marine aerosol abundances, giving further support to a recently postulated primary OC source in the remote marine atmosphere.

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“…Assuming an OH concentration of 3 × 10 6 molec/cm 3 and an atmospheric life time of CHO-CHO of 2 h (conservative upper limit), the VOC concentration needed to explain 100 ppt of CHOCHO is either 600 ppt of isoprene, 2.8 ppb toluene, or 8.9 ppb acetylene, or lower concentrations if multiple compounds were present. There are few observations of VOCs over the remote open ocean, and most of them focus on isoprene (Bonsang et al, 1992;Broadgate et al, 1997Broadgate et al, , 2004Baker et al, 2000;Matsunaga et al, 2002;Meskhidze and Nenes, 2006;Yassaa et al, 2008). The currently measured isoprene concentrations do not exceed 40 ppt and mostly are on the order of 10 ppt.…”

Section: Discussionmentioning

confidence: 99%

Ship-based detection of glyoxal over the remote tropical Pacific Ocean

et al. 2010

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Abstract. We present the first detection of glyoxal (CHO-CHO) over the remote tropical Pacific Ocean in the Marine Boundary Layer (MBL). The measurements were conducted by means of the University of Colorado Ship Multi-Axis Differential Optical Absorption Spectroscopy (CU SMAX-DOAS) instrument aboard the research vessel Ronald H. Brown. The research vessel was on a cruise in the framework of the VAMOS Ocean-Cloud-Atmosphere-Land Study -Regional Experiment (VOCALS-REx) and the Tropical Atmosphere Ocean (TAO) projects lasting from October 2008 through January 2009 (74 days at sea). The CU SMAX-DOAS instrument features a motion compensation system to characterize the pitch and roll of the ship and to compensate for ship movements in real time. We found elevated mixing ratios of up to 140 ppt CHOCHO located inside the MBL up to 3000 km from the continental coast over biologically active upwelling regions of the tropical Eastern Pacific Ocean. This is surprising since CHOCHO is very short lived (atmospheric life time ∼2 h) and highly water soluble (Henry's Law constant H = 4.2 × 10 5 M/atm). This CHOCHO cannot be explained by transport of it or its precursors from continental sources. Rather, the open ocean must be a source for CHOCHO to the atmosphere. Dissolved Organic Matter (DOM) photochemistry in surface waters is a source for Volatile Organic Compounds (VOCs) to the atmosphere, e.g. acetaldehyde. The extension of this mechanism to very soluble gases, like CHOCHO, is not straightforward since the air-sea flux is directed from the atmosphere into the ocean. For CHOCHO, the dissolved concentrations would need to be extremely high in order to explain our gas-phase observations by this mechanism (40-70 µM CHOCHO, comparedCorrespondence to: R. Volkamer (rainer.volkamer@colorado.edu) to ∼0.01 µM acetaldehyde and 60-70 µM DOM). Further, while there is as yet no direct measurement of VOCs in our study area, measurements of the CHOCHO precursors isoprene, and/or acetylene over phytoplankton bloom areas in other parts of the oceans are too low (by a factor of 10-100) to explain the observed CHOCHO amounts. We conclude that our CHOCHO data cannot be explained by currently understood processes. Yet, it supports first global source estimates of 20 Tg/year CHOCHO from the oceans, which likely is a significant source of secondary organic aerosol (SOA). This chemistry is currently not considered by atmospheric models.

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Distribution and sea‐air fluxes of biogenic trace gases in the eastern Atlantic Ocean

Abstract: Abstract. A number of atmospherically important trace gases (dimethyl sulphide (DMS),

Cited by 101 publications

References 67 publications

Iodine speciation and deposition fluxes from the marine atmosphere

Iodine speciation and deposition fluxes from the marine atmosphere

Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol

Ship-based detection of glyoxal over the remote tropical Pacific Ocean

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