Surface Ocean - Lower Atmosphere Study (SOLAS) Project Integration

Short-lived trace gases and particles

Implementation Working Group one (IMP 1) focuses upon the following

Go to the top of this page

Dimethyl Sulphide (DMS)

The biogenic trace gas, DMS, is well known for its role in the proposed CLAW hypothesis (Charlson et al., 1987). In terms of data archiving, this compound is the most advanced in IMP 1, primarily due to the work of Jamie Kettle, who produced the original database of 15,617 surface DMS concentration measurements (Kettle et al., 1999).

This work was then further developed and reanalysed (Kettle and Andreae, 2000) before the creation of an existing online DMS database, which is maintained and updated by Tim Bates and James Johnson at the National Oceanic and Atmospheric Administration (NOAA), USA. The database now contains 31,589 surface measurements (February 2007).

A recent joint initiative between the Institut de Ciencies del Mar de Barcelona (ICM-CSIC) and the University of East Anglia has been supported by the SOLAS IPO and COST Action 735. This has provided funds for Arancha Lana to reanalyse the updated DMS database, in order to produce a new DMS climatology. Anyone with data they have not yet submitted should follow the DMS data contribution instructions. These contain details concerning the spreadsheets necessary for submission, and instructions for submitting data.

References
  1. Charlson, R.J., et al. (1987) Oceanic phytoplankton, atmospheric sulfur, cloud albedo and climate. Nature 326: 655-661.
  2. Kettle, A.J. et al. (1999) A global database of sea surface dimethylsulfide (DMS) measurements and a procedure to predict sea surface DMS as a function of latitude, longitude, and month. GBC 13(2): 399-444.
  3. Kettle, A.J. and Andreae, M.O. (2000) Flux of dimethylsulfide from the oceans: A comparison of updated data seas and flux models. JGR-Atmospheres, 105(D22): 26793-26808.
Go to the top of this page

Organohalogens

Short-lived brominated and iodinated halocarbons (or organohalogens) from oceanic sources are important halogen-carriers to both the troposphere and stratosphere. Reactive halogen compounds are formed in significant quantities via the breakdown of organohalogens and are critical to oxidising capacity in the troposphere, and significant contributors to ozone depletion in the stratosphere (Law & Sturges et al., 2006; Ko & Poulet et al., 2002). In addition, it has been suggested that biogenic iodocarbon emissions may play a role in new particle formation in the atmosphere (O'Dowd et al., 2002). Methyl iodide (CH3I) is of particular interest from this perspective as it is one of the major means by which iodine gets into the gas phase and into the atmosphere, although other very short-lived iodocarbons may also play a role (Carpenter et al., 2000). Likewise, bromoform (CHBr3) is the dominant source of organic bromine to the troposphere and lower stratosphere (Quack and Wallace, 2003). Recently, the Halogens in the Troposphere (HitT) task team have produced the HitT White Paper, in which they outline how research into halogenated compounds should proceed (see their webpage for more details).

An important aspect of understanding the tropospheric halogen budget is the net flux of volatile organohalogens from the ocean to the atmosphere. Our understanding of the contribution of these important halogen sources to stratospheric and tropospheric chemistry is limited in part by a lack of calibration and comparison of measurements among laboratories. For example, several studies have highlighted a high variability in marine concentrations and atmospheric fluxes of these gases (e.g., Carpenter et al., 2003; Butler et al., 2007). However, it is not always clear how much of the variation results from natural spatial and temporal differences or from analytical dissimilarities or calibration. An advancement of data compatibility will improve the:

  1. understanding of the relative contributions of organic and inorganic forms to the reactive species that drive oxidation;
  2. assessment of the impacts of climate change on atmospheric chemistry;
  3. value and validity of common databases.

Seeking to address this increasingly-relevant issue, thirty-two scientists (details) from eight nations gathered in February 2008 at the Novartis Institute in London. This workshop was made possible by the support of the SOLAS International Project Office (IPO); the Natural Environment Research Council (NERC) through UK-SOLAS Knowledge Transfer funds; and the European Science Foundation (ESF) through COST (Cooperation in the field of Scientific and Technical Research) Action 735 funds.

The aim of this workshop was to plan for an international effort that will ensure traceability to common calibration scales for marine measurements of short-lived, volatile halocarbons. The workshop agenda focused on determining the scope of the scientific need, identifying which compounds should be targeted for the greatest scientific benefit, identifying opportunities for beginning calibration and comparison efforts, and prescribing a way forward for improving the comparability of measurements.

Discussions were led by presentations (links to presentation pdfs are in brackets), specifically:

  1. the scientific importance of these observations (Bell and Butler);
  2. the needs of the modeling community in terms of the detection limitations of the instrumentation (von Glasow);
  3. the lack of understanding of the variability of these compounds due to measurement uncertainties (Carpenter and Blake);
  4. methods and potential inter-calibration techniques (Hall and Quack).

More detailed reports of these discussions have been written for the SOLAS Newsletter and for the COST Action 735 management committee.

Anybody who is involved in making marine measurements of short-lived halocarbon compounds (aqueous or gas phase) who would like to be involved in any future inter-calibration effort, please contact the SOLAS Project Integrator.

References
  1. Butler, J.H., King, D.B., Lobert, J.M., Montzka, S.A., Yvon-Lewis, S.A., Hall, B.D., Warwick, N.J., Mondeel, D.J., Aydin, M., Elkins, J.W., 2007. Oceanic distributions and emissions of short-lived halocarbons. Global Biogeochemical Cycles, 21 (1), art. no.-GB1023.
  2. Carpenter, L.J., Malin, G., Liss, P.S., Kupper, F.C., 2000. Novel biogenic iodine-containing trihalomethanes and other short-lived halocarbons in the coastal East Atlantic. Global Biogeochemical Cycles, 14 (4), 1191-1204.
  3. Carpenter, L.J., 2003. Iodine in the marine boundary layer. Chemical Reviews, 103 (12), 4953-4962.
  4. Ko, M.K.W. and Poulet, G. (Lead Authors) Blake, D.R., Boucher, O., Burkholder, J.H., Chin, M., Cox, R.A., George, C., Graf, H.-F., Holton, J.R., Jacob, D.J., Law, K.S., Lawrence, M.G., Midgley, P.M., Seakins, P.W., Shallcross, D.E., Strahan, S.E., Wuebbles, D.J., and Yokouchi, Y. (2002) Very short-lived halogen and sulfur substances. Chapter 2 in Scientific Assessment of Ozone Depletion: 2002 Global Ozone Research and Monitoring Project–Report No. 47, World Meteorological Organization, Geneva, Switzerland, 2003.
  5. Law, K.S. and Sturges, W.T. (Lead Authors) Blake, D.R., Blake, N.J., Burkholder, J.B., Butler, J.H., Cox, R.A., Haynes, P.H., Ko, M.K.W., Kreher, K., Mari, C., Pfeilsticker, K., Plane, J.M.C., Salawitch, R.J., Schiller, C., Sinnhuber, B.-M., von Glasow, R., Warwick, N.J., Wuebbles, D.J., Yvon-Lewis, S.A. (2006) Halogenated very short-lived substances. Chapter 2 in Scientific Assessment of Ozone Depletion: 2006 Global Ozone Research and Monitoring Project–Report No. 50, World Meteorological Organization, Geneva, Switzerland, 2007.
  6. O'Dowd, C.D., Jimenez, J.L., Bahreini, R., Flagan, R.C., Seinfeld, J.H., Hameri, K., Pirjola, L., Kulmala, M., Jennings, S.G., Hoffmann, T., 2002. Marine aerosol formation from biogenic iodine emissions. Nature, 417 (6889), 632-636.
  7. Quack, B., Wallace, D.W.R., 2003. Air-sea flux of bromoform: Controls, rates, and implications. Global Biogeochemical Cycles, 17 (1), art. no.-GB1023.
Go to the top of this page

Alkyl nitrates (RONO2)

Despite accounting for a substantial proportion of the tropospheric reactive nitrogen pool, alkyl nitrates, including methyl nitrate, have received relatively little attention thus far. Published work appears limited to a small number of research campaigns (Chuck et al., 2002; Moore and Blough, 2002; Dahl et al., 2005; Dahl et al., 2007).

References
  1. Chuck, A.L. et al. (2002) Direct evidence for a marine source of C1 and C2 alkyl nitrates. Science 297(5584): 1151-1154.
  2. Dahl, E.E. et al. (2005) Saturation anomalies of alkyl nitrates in the tropical Pacific Ocean. GRL 32(20): art. no.-L20817.
  3. Dahl, E.E. et al. (2007) Alkyl nitrate (C1-C3) depth profiles in the tropical Pacific Ocean. JGR 112: art. no. -C01012.
  4. Moore, R.M. and Blough, N.V. (2002) A marine source of methyl nitrate. GRL 29(15): art. no.-1737.
Go to the top of this page

Isoprene (C5H8)

Very little work has been carried out on this compound, but from recent results it has been proposed that, once produced by phytoplankton, isoprene may play a significant role in cloud formation over the Southern Ocean (Meskhidze and Nenes, 2006). No data set currently exists for isoprene.

References
  1. Meskhidze, N. and Nenes, A. (2002) Phytoplankton and cloudiness in the Southern Ocean. Science 314(5804): 1419-1423.
Go to the top of this page

Methanol (CH3OH)

Methanol has a significant impact upon the oxidising capacity of the atmosphere and can oxidise sulphuric acid (H2SO4) to methane sulphonate MSA in cloud droplets (Singh et al., 2000). It has been demonstrated that terrestrial plants may represent a sizeable source of methanol to the atmosphere (Riemer et al., 1998), while preliminary studies of algal cultures suggest that oceanic phytoplankton may also produce methanol (see Heikes et al., 2002).

Based on concentrations measured in the troposphere and lower stratosphere (Singh et al., 2000) and the conclusions of budgetary modeling studies (Heikes et al., 2002), it has been suggested that the ocean may be a substantial source of methanol. However, recent results indicate that the North Atlantic may in fact be a net sink for methanol (Carpenter et al., 2004; Williams et al., 2004).

More oceanic measurements of methanol are required to substantiate the opposing conclusions presented so far. Please could any data that has been collected be submitted to the Project Integrator.

References
  1. Carpenter, L.J. et al. (2004) Uptake of methanol to the North Atlantic Ocean surface. GBC 18: art. no.-GB4027.
  2. Williams J., et al. (2004) Measurements of organic species in air and seawater from the tropical Atlantic. GRL 31: art. no.-L23S06.
  3. Heikes, B.J. et al. (2002) Atmospheric methanol budget and ocean implication. GBC 16(4): art. no.-1133.
  4. Riemer, D. et al (1998) Observations of nonmethane hydrocarbons and oxygenated volatile organic compounds at a rural site in the southeastern United States. JGR 103: 28111-28128.
  5. Singh, H. et al. (2000) Distribution and fate of selected oxygenated organic species in the troposphere and lower stratosphere over the Atlantic. JGR 105: 3795-3805.
Go to the top of this page

Ammonia (NH3)

The air-sea exchange of ammonia is important as acid-base reactions in the atmosphere efficiently form fine mode aerosol ammonium sulphate by gas to particle conversion (Raes et al., 2000). It has also been argued that ammonia allows more rapid formation of new aerosol particles (Yu, 2003), which have a relatively high light scattering coefficient and are also efficient cloud condensation nuclei.

Due to the intensification of agricultural practice, the dominant global source of atmospheric NH3 is terrestrial and this has significant impacts on the present air-sea flux. In contrast, measurements in the remote marine environment have proven difficult due to the low concentrations in both atmosphere and ocean. Despite this, there are indications that the flux may sometimes be from the ocean to the atmosphere (Jickells et al., 2003).

No global data set currently exists of ocean/atmosphere NH3 concentrations.

References
  1. Jickells, T.D. et al. (2003) Isotopic evidence for a marine ammonia source. GRL 30: art. no.-1374.
  2. Raes F. et al. (2000) Formation and cycling of aerosols in the global troposphere. Atm Env 34: 4215-4240.
  3. Yu, F. Q. (2003) Nucleation rate of particles in the lower atmosphere: Estimated time needed to reach pseudo-steady state and sensitivity to H2SO4 gas concentration. GRL 30: art. no.-1526.
Go to the top of this page

Aerosol and rain composition and deposition

Aerosol composition determines the input of atmospheric nutrients to the surface ocean. In the remote marine environment this input can have a significant impact on the biological system. Despite being an active area of research, very few aerosol measurements made over the oceans have been archived in a systematic manner.

A recent initiative under the EU-funded COST Action 735 (details) aims to collate ship-based aerosol measurements on a global scale. Details concerning the type(s) of data of interest, the spreadsheets necessary for submission and instructions for submitting data can be found in the data submission area. Note that this data collation project will adhere to the SOLAS Project Integration Data Policy.

Go to the top of this page