[Full report: direct quote from NOC website]
下文有各分項文字說明，覺得是一個不錯的初步瞭解。
Understanding gas exchange at the air-sea interface and its impact on climate
Scientists from the National Oceanography Centre, Southampton are making a significant contribution to an ambitious international programme (SOLAS; the Surface Ocean–Lower Atmosphere Study) aimed at understanding the physical, chemical and biological processes that determine the exchange of greenhouse and other important gases between the oceans and the atmosphere. The programme findings will greatly advance our understanding of climate change; the individual projects and latest results are described in the Bulletin of the American Meteorological Society.
Gas exchange between the air and the sea exerts a significant control on atmospheric composition and thus on climate change. Such exchange is affected by many factors including wind speed, wave slopes, whitecapping, wave breaking, bubble bursting, sea surface temperature, rainfall, and the presence of surfactants. These and other factors have a huge influence on the flux of greenhouse gases such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), as well as dimethyl sulfide (DMS), which affects climate when oxidised to form aerosol particles on which cloud droplets can form. Many of these physical processes also affect the produc¬tion of aerosol from sea spray. Sea salt aerosol scatters solar radia¬tion over the open ocean under clear skies, and influences cloud chemistry.
Quantifying all of the factors that affect gas exchange at the sea surface is important for climate models, long-term forecasts, and assessing future climate. As part of the UK contribution to SOLAS, several related projects undertook field studies of the exchange processes. This involved several research cruises and the deployment of a suite of sophisticated instruments.
HiWASE (High Wind Air-Sea Exchanges) aims to produce a dataset of unprecedented size and detail by instrumenting a ship to obtain flux measurements con¬tinuously for three years, under a variety of conditions including high wind speed events. The project is expected to operate until at least 2009 and uses instruments installed on the Polarfront – the world’s last weather ship run by the Norwegian Meteorological Institute. The ship operates in a region of the Norwegian Sea that experiences both large CO2 fluxes and frequent high-wind events.
The equipment on the Polarfront includes an automated system for the direct measurement of air–sea fluxes – AutoFlux – installed by the National Oceanography Centre, Southampton (NOCS) in September 2006. The instrumentation can operate autonomously over a period of several years sending daily data summaries via a satellite link. “This approach allows for the collection of a much larger dataset than is possible from typical research cruises,” says Margaret Yelland, project PI.
SEASAW (Sea Spray, Gas Flux and Whitecap) focuses on the production, composition and fate of sea-spray aerosol particles close to the ocean surface, as well as CO2 fluxes associated with ocean eddies. Amongst the many instruments deployed were an AutoFlux system (NOCS) and a new aerosol spectrometer, the Compact Lightweight Aerosol Spectrometer Probe (CLASP, University of Leeds) , which has allowed direct size-resolved measurements of the sea-spray aerosol flux to be made for the first time.
DOGEE (Deep Ocean Gas Exchange Experiment) uses tracer release experiments to estimate the gas transfer velocity and how this is affected by surfactants, sea-state, and near-surface turbulence. CO2, oxygen, nitrogen and DMS fluxes were measured, as well as heat in the water column, and the presence of gaseous oxygenated volatile organic compounds. Waves were measured and recorded using instruments on buoys, including a spar buoy deployed by the National Oceanography Centre, Southampton to study wave breaking and whitecapping. The spar buoy was also equipped with two acoustic and one optical system for determining the bubble population. These bubble systems were installed by Tim Leighton’s group at the University of Southampton’s Institute of Sound and Vibration Research (ISVR).
“The HiWASE, SEASAW, and DOGEE field programs share a common goal: to understand the processes controlling physical exchanges at the air–sea interface and to extend measurements of gas transfer to high wind speeds”, say the researchers. SEASAW and DOGEE involved a total of three re¬search cruises in the northeast Atlantic on board the RRS Discovery in 2006 and 2007, while HiWASE is ongoing.
“These UK–SOLAS surface exchange field programs have provided a wealth of new data,” say the researchers. Highlights include: the first multiple patch dual-tracer release experiment; the first deliberate surfactant release experi¬ments; measurements of gas flux at high wind speeds; the ongoing acquisition of a continuous, multiyear set of direct gas flux measurements over the open ocean; measurements of fully size-resolved sea-spray aerosol fluxes associated with ocean eddies; simultaneous measurement of air–sea fluxes of multiple trace gases by multiple techniques; and comprehensive sea-state and whitecap measure¬ments from buoy and ship systems simultaneous with gas and aerosol flux measurements.
Such wide-ranging measurements will enable the assessment of the influence of most of the physical processes affecting gas exchange and sea spray aerosol production and will be important for improved parameterisations in climate models. “The strong links between the three projects enhances their individual strengths, extending the range of measurement con¬ditions, facilitating direct comparisons between multiple techniques, and enabling the truly interdis¬ciplinary approach required to properly understand physical exchange at the air–sea interface”, conclude the researchers.
The paper, entitled ‘Physical Exchanges at the Air–Sea Interface UK–SOLAS Field Measurements’ is published in the Bulletin of the American Meteorological Society.
The UK–SOLAS projects were funded by the UK Natural Environment Research Council and by the US National Science Foundation. The research was conducted aboard the RRS Discovery and the Norwegian weather ship Polarfront.
The full author list is: Ian Brooks, Margaret Yelland, Robert Upstill-Goddard, Philip Nightingale, Steve Archer, Ericd’Asaro, Rachael Beale, Cory Beatty, Byron Blomquist, Anthony Bloom, Barbara Brooks, John Cluderay, David Coles, John Dacey, Michael DeGrandpre, Jo Dixon, William Drennan, Joseph Gabriele, Laura Goldson, Nick Hardman-Mountford, Martin Hill, Matt Horn, Ping-Chang Hsueh, Barry Huebert, Gerrit de Leeuw, Timothy Leighton, Malcolm Liddicoat, Justin Lingard, Craig McNeil, James McQuaid, Ben Moat, Gerald Moore, Craig Neill, Sarah Norris, Simon O’Doherty, Robin Pascal, John Prytherch, Mike Rebozo, Erik Sahlee, Matt Salter, Ute Schuster, Ingunn Skjelvan, Hans Slagter, Michael H. Smith, Paul Smith, Meric Srokosz, John Stephens, Peter Taylor, MaciejTelszewski, Roisin Walsh, Brian Ward, David Woolf, Dickon Young, and Henk Zemmelink.
In addition to the National Oceanography Centre, Southampton, the institutions contributing to SOLAS are the Universities of Southampton, Leeds, Newcastle, Washington, Montana, Hawaii at Manoa, Miami, Rhode Island, Helsinki, Bergen, Bristol, East Anglia, Groningen, and Galway, as well as the Norwegian Meteorological Institute, Plymouth Marine Laboratory, the Royal Netherlands Institute for Sea Research (NIOZ), Woods Hole Oceanographic Institution, the Rosenstiel School of Marine and Atmospheric Science, the Canadian National Water Research Institute, the Finnish Meteorological Institute, and the Woolf-UHI Millennium Institute (Thurso).
Details of the instrumentation used are given online: http://dx.doi.org/10.1175/2008BAMS2578.2
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