Surface Ocean - Lower Atmosphere Study (SOLAS) Project Integration

Long-lived climatically-active gases

Implementation Working Group three (IMP 3) focuses upon the following

Go to the top of this page

Carbon dioxide (CO2)

Given its global relevance as a greenhouse gas and the fact that the global surface ocean is a significant net sink for anthropogenic CO2, it is unsurprising that a large amount of scientific attention has been focused upon surface ocean CO2 partial pressure (pCO2).

The largest global data centre for pCO2 measurements is the Carbon Dioxide Information Analysis Center (CDIAC), through which all publicly available pCO2 data can be accessed. These data can be subdivided into surface ocean Volunteer Observing Ship (VOS) data; and moorings and timeseries data.

Graphical representation of pCO2 data sources has been put together by Dr Maria Hood at the International Ocean Carbon Coordination Project (IOCCP) Ocean Carbon Directory for VOS data sources and moorings and timeseries projects.

Anyone with surface pCO2 data that is not in the CDIAC database, please contact Alex Kozyr (CDIAC) directly.

Go to the top of this page

Methane (CH4)

Methane (CH4) is an important biogenic trace gas with a relatively long tropospheric lifetime of around a decade (Lelieveld et al., 1998).  It is infrared-active, accounting for about 20% of enhanced greenhouse forcing (IPCC, 2007).  Tropospheric methane has a variety of global sources, of which more than one half are anthropogenic.  Natural sources are dominated by wetlands but marine emissions also contribute (IPCC, 2007).  Reaction with tropospheric OH is the primary atmospheric CH4 sink (Crutzen, 1995).  Short-term changes in the relative strengths of source and sink functions are reflected in a tropospheric CH4 growth rate that is annually variable.  Since the beginning of 2007, the trend has been one of consistent growth (Rigby et al., 2008), but unfortunately the interactions that govern this variability are not well understood.

Methane is generally supersaturated in surface ocean waters.  Current ‘best’ estimates are that <5% of tropospheric CH4 is of marine origin; however data coverage is rather poor and these estimates still tend to be dominated by open ocean regions where the degree of surface CH4 supersaturation is relatively mild.  Contributions from estuaries and shallow coastal shelves are far larger per unit area (e.g. Bange et al., 1994; Upstill-Goddard et al., 2000), implying that such estimates require revision.

Improving our current estimates of marine CH4 emissions is therefore a key priority.  A recent initiative under COST Action 735, called MEMENTO, aims to integrate existing oceanic and atmospheric measurements into a global database (see Bange et al., 2009).  For further details of MEMENTO, please also see the outline document.  Details concerning the spreadsheets necessary for submission are available along with instructions for submitting data.

References
  1. Bange, H.W., Bartell, U.H., Rapsomanikis, S. and Andreae, M.O., 1994. Methane in the Baltic and North Seas and a reassessment of the marine emissions of methane. Global Biogeochemical Cycles, 8(4): 465-480.
  2. Bange, H.W., Bell, T.G., Cornejo, M., Freing, A., Uher, G., Upstill-Goddard, R.C. and Zhang, G., 2009. MEMENTO: A proposal to develop a database of marine nitrous oxide and methane measurements. Environmental Chemistry, Submitted.
  3. Crutzen, P.J., 1995. Overview of tropospheric chemistry: Developments during the past quarter century and a look ahead. Faraday Discussions, 100: 1-21.
  4. IPCC, 2007. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. In: S. Solomon et al. (Editors), Climate Change 2007: The Physical Science Basis. Cambridge University Press, Cambridge, UK and New York, USA.
  5. Lelieveld, J., Crutzen, P.J. and Dentener, F.J., 1998. Changing concentration, lifetime and climate forcing of atmospheric methane. Tellus Series B-Chemical and Physical Meteorology, 50(2): 128-150.
  6. Rigby, M., Prinn, R.G., Fraser, P.J., Simmonds, P.G., Langenfelds, R.L., Huang, J., Cunnold, D.M., Steele, L.P., Krummel, P.B., Weiss, R.F., O'Doherty, S., Salameh, P.K., Wang, H.J., Harth, C.M., Muhle, J. and Porter, L.W., 2008. Renewed growth of atmospheric methane. Geophysical Research Letters, 35(22).
  7. Upstill-Goddard, R.C., Barnes, J., Frost, T., Punshon, S. and Owens, N.J.P., 2000. Methane in the southern North Sea: Low-salinity inputs, estuarine removal, and atmospheric flux. Global Biogeochemical Cycles, 14(4): 1205-1217.
Go to the top of this page

Nitrous oxide (N2O)

Nitrous oxide (N2O) is an important atmospheric trace gas.  In the troposphere it acts as a strong greenhouse gas and in the stratosphere it is the major precursor of the ozone-depleting nitric oxide radical.  Moreover, the last 100 years have seen a significant increase in atmospheric N2O concentrations.  Oceanic N2O emissions play a major role in the atmospheric N2O budget (e.g. Bange, 2006).  

In the 4th assessment report of the Intergovernmental Panel on Climate Change (IPCC), mean annual N2O emissions (ranges are given in parenthesis) of 3.8 (1.8 – 5.8) Tg N and 1.7 (0.5 – 2.9) Tg N were attributed to the open ocean and coastal areas (including rivers), respectively (IPCC, 2007).  This represents 21% (open ocean) and 10% (coastal including rivers) of all N2O sources (IPCC, 2007).  

There are various reasons for the considerable ranges of uncertainty in the global N2O emission estimates (Bange, 2008):

  1. different methodological approaches (empirical models versus extrapolation of measurements);
  2. the application of different air-sea exchange models;
  3. the fact that the applied classification of coastal areas is not uniform.

Improving our current estimates of marine N2O emissions is therefore a key priority.  A recent initiative under COST Action 735, called MEMENTO, aims to integrate existing oceanic and atmospheric measurements into a global database (see Bange et al., 2009).  For further details of MEMENTO, please also see the outline document and an article written for the IMBER newsletter.  Details concerning the spreadsheets necessary for submission are available, along with instructions for submitting data.

References
  1. Bange, H.W., 2006. New Directions: The importance of oceanic nitrous oxide emissions. Atmospheric Environment, 40(1): 198-199.
  2. Bange, H.W., 2008. Gaseous nitrogen compounds (NO, N2O, N2, NH3) in the ocean. In: D.G. Capone, D.A. Bronk, M.R. Mulhollad and E.J. Carpenter (Editors), Nitrogen in the Marine Environment. Elsevier, Amsterdam, pp. 51-94.
  3. Bange, H.W., Bell, T.G., Cornejo, M., Freing, A., Uher, G., Upstill-Goddard, R.C. and Zhang, G., 2009. MEMENTO: A proposal to develop a database of marine nitrous oxide and methane measurements. Environmental Chemistry, Submitted.
  4. IPCC, 2007. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. In: S. Solomon et al. (Editors), Climate Change 2007: The Physical Science Basis. Cambridge University Press, Cambridge, UK and New York, USA.
Go to the top of this page