World Ocean Circulation Experiment

The World Ocean Circulation Experiment (WOCE) was a component of the international World Climate Research Program, and aimed to establish the role of the World Ocean in the Earth's climate system. WOCE's field phase ran between 1990 and 1998, and was followed by an analysis and modeling phase that ran until 2002.^[1] When the WOCE was conceived, there were three main motivations for its creation. The first of these is the inadequate coverage of the World Ocean, specifically in the Southern Hemisphere. Data was also much more sparse during the winter months than the summer months, and there was—and still to some extent—a critical need for data covering all seasons. Secondly, the data that did exist was not initially collected for studying ocean circulation and was not well suited for model comparison. Lastly, there were concerns involving the accuracy and reliability of some measurements. The WOCE was meant to address these problems by providing new data collected in ways designed to “meet the needs of global circulation models for climate prediction.” ^[2]

Goals

Two major goals were set for the campaign.^[1]

1. Develop ocean models that can be used in climate models and collect the data necessary for testing them. Specifically, understand:

Large scale fluxes of heat and fresh water
Dynamical balance of World Ocean circulation
Components of ocean variability on months to years
The rates and nature of formation, ventilation and circulation of water masses that influence the climate system on time scales from ten to one hundred years ^[3]

In order to achieve Goal 1, the WCRP outlined and established Core Projects that would receive priority. The first of these was the “Global Description” project, which was meant to obtain data on the circulation of heat, fresh water and chemicals, as well as the statistics of eddies. The second project—“Southern Ocean”—placed particular emphasis on studying the Antarctic Circumpolar Current and the Southern Ocean’s interaction with the World Ocean. The third and final Core Project serving goal one was the “Gyre Dynamics Experiment.” The second and third of these focuses are designed specifically to address the ocean’s role in decadal climate changes. Initial planning of the WOCE states that achievement of Goal 1 would involve “strong interaction between modeling and field activities,” which are described further below.

2. Find the representativeness of the dataset for long-term behavior and find methods for determining long-term changes in ocean currents. Specifically:

Determine representative of specific WOCE data sets
Identify those oceanographic parameters, indices and fields that are essential for continuing measurements in a climate observing system on decadal time scales
Develop cost effective techniques suitable for deployment in an ongoing climate observing system^[3]

Modeling

Models in WOCE were used for both experimental design and data analysis. Models with use of data can incorporate various properties, including thermal wind balance, maintenance of the barotropic vorticity budget, and conservation of heat, fresh water, or mass. Measurements useful for these parameters are heat, fresh water or tracer concentration; current, surface fluxes of heat and fresh water; sea surface elevation.^[3]

Both inverse modeling and data assimilation were employed during WOCE. Inverse modeling is the fitting of data using a numerical least squares or maximum likelihood fitting procedure. The data assimilation technique requires data to be compared with an initial integration of a model. The model is then progressed in time using new data and repeating the process.^[3]

The success of these methods requires sufficient data to fully constrain the model, hence the need for a comprehensive field program.

Field Program

Goals for the WOCE Field Program were as follows.^[1]

The experiment will be global in nature and the major observational components will be deployed in all oceans.
The requirement of simultaneity of measurements will be imposed only where absolutely essential.
The flexibility inherent in the existing arrangements for cooperative research in the worldwide oceanographic (and meteorological) community will be exploited as far as possible.

Major elements of the WOCE Field Program ^[3]

Satellite Altimetry: plans built around the availability of ERS–1 and ERS–2 (European), TOPEX/POSEIDON (US/French) to study fields of surface forcing and oceanic surface topography ^[2]
Hydrography: high quality conductivity-temperature-pressure profilers as well as free-fall instruments to provide a climatological temperature-salinity database ^[2]
Geochemical Tracers: using chemical information (such as radioactive decay and atmospheric history) of passive compounds to study the formation rates and transport of water masses on climatological timescales
Ocean Surface Fluxes: using in-situ and satellite measurements to quantify fluxes of heat, water and momentum (necessary for modeling thermohaline and wind-driven circulation)
Satellite Winds: using surface buoys, Voluntary Observing Ships (VOS) and satellite microwave scatterometer systems to measure the surface wind field
Surface Meteorological Observations from VOS: improvement of sampling and accuracy in surface meteorological measurements, as well increasing area coverage
Upper Ocean Observations from Merchant Ships-of-Opportunity: expendable bathythermograph (XBT) sampling lines to study changes in heat content of the upper ocean
In-Situ Sea Level Measurements: upgrading and installing new sea-level gauges to calibrate altimetry measurements
Drifting Buoys and Floats: surface drifting buoys provide measurements such as sea level pressure, sea-surface temperature, humidity, precipitation, surface salinity, and near-surface and mid-depth currents
Moored instrumentation: provides detailed temporal information at a number of sites and depths

Resulting Conclusions

This list, though not comprehensive, outlines a sampling of the most highly cited papers resulting from the WOCE.

Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data

   A. Ganachaud & C. Wunsch
   Nature, November 2000

Volume, heat, and freshwater transports of the global ocean circulation 1993–2000, estimated from a general circulation model constrained by World Ocean Circulation Experiment (WOCE) data

   D. Stammer, C. Wunsch, R. Giering, C. Eckert, P. Heimbach, J. Marotzke, A. Adcroft, C. N. Hill, J. Marshall
   Journal of Geophysical Research, January 2003

Large-scale mass transports, water mass formation, and diffusivities estimated from World Ocean Circulation Experiment (WOCE) hydrographic data

   A. Ganachaud
   Journal of Geophysical Research, July 2003

Oceanic nutrient and oxygen transports and bounds on export production during the World Ocean Circulation Experiment

   A. Ganachaud, Carl Wunsch
   Global Biogeochemical Cycles, October 2002

Revisiting the South Pacific subtropical circulation: A synthesis of World Ocean Circulation Experiment observations along 32°S

   S. E. Wijffels, J. M. Toole, R. Davis
   Journal of Geophysical Research, September 2012

External links

Access page to the WOCE data legacy at the National Oceanographic Data Center (US)
Electronic Atlas of WOCE Data at the Alfred Wegener Institute for Polar and Marine Research, Bremerhaven
WOCE page at the National Oceanography Centre, Southampton (UK)
Searchable set of WOCE data, archived in the information system PANGAEA
WOCE observations 1990-1998; a summary of the WOCE global data resource, WOCE International Project Office, WOCE Report No. 179/02., Southampton, UK. (pdf 18.9 MB)

References

Physical oceanography

Waves	Airy wave theory Ballantine scale Benjamin–Feir instability Boussinesq approximation Breaking wave Clapotis Cnoidal wave Cross sea Dispersion Edge wave Equatorial waves Fetch Gravity wave Green's law Infragravity wave Internal wave Kelvin wave Kinematic wave Longshore drift Luke's variational principle Mild-slope equation Radiation stress Rogue wave Rossby wave Rossby-gravity waves Sea state Seiche Significant wave height Sneaker wave Soliton Stokes boundary layer Stokes drift Stokes wave Swell Trochoidal wave Tsunami megatsunami Undertow Ursell number Wave action Wave base Wave height Wave power Wave radar Wave setup Wave shoaling Wave turbulence Wave–current interaction Waves and shallow water one-dimensional Saint-Venant equations shallow water equations Wind wave model

Circulation	Atmospheric circulation Baroclinity Boundary current Coriolis effect Downwelling Eddy Ekman layer Ekman spiral Ekman transport El Niño Southern Oscillation General Circulation Model Geostrophic current Global Ocean Data Analysis Project Gulf Stream Halothermal circulation Humboldt Current Hydrothermal circulation Langmuir circulation Longshore drift Loop Current Maelstrom Modular ocean model Ocean dynamics Ocean gyre Princeton ocean model Rip current Subsurface currents Sverdrup balance Thermohaline circulation shutdown Upwelling Whirlpool World Ocean Circulation Experiment

Tides	Amphidromic point Earth tide Head of tide Internal tide Lunitidal interval Perigean spring tide Rip tide Rule of twelfths Slack water Tidal bore Tidal force Tidal power Tidal race Tidal range Tidal resonance Tide gauge Tideline

Landforms	Abyssal fan Abyssal plain Atoll Bathymetric chart Coastal geography Cold seep Continental margin Continental rise Continental shelf Contourite Guyot Hydrography Oceanic basin Oceanic plateau Oceanic trench Passive margin Seabed Seamount Submarine canyon Submarine volcano

Plate tectonics	Convergent boundary Divergent boundary Fracture zone Hydrothermal vent Marine geology Mid-ocean ridge Mohorovičić discontinuity Vine–Matthews–Morley hypothesis Oceanic crust Outer trench swell Ridge push Seafloor spreading Slab pull Slab suction Slab window Subduction Transform fault Volcanic arc

Ocean zones	Benthic Deep ocean water Deep sea Littoral Mesopelagic Oceanic Pelagic Photic Surf Swash

Sea level	Deep-ocean Assessment and Reporting of Tsunamis Future sea level Global Sea Level Observing System North West Shelf Operational Oceanographic System Sea-level curve Sea level rise World Geodetic System

Acoustics	Deep scattering layer Hydroacoustics Ocean acoustic tomography Sofar bomb SOFAR channel Underwater acoustics

Satellites	Jason-1 Jason-2 (Ocean Surface Topography Mission) Jason-3

Related	Argo Benthic lander Color of water DSV Alvin Marginal sea Marine energy Marine pollution Mooring National Oceanographic Data Center Ocean Ocean exploration Ocean observations Ocean reanalysis Ocean surface topography Ocean thermal energy conversion Oceanography Pelagic sediment Sea surface microlayer Sea surface temperature Seawater Science On a Sphere Thermocline Underwater glider Water column World Ocean Atlas

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