Global Drifter Program

This is a snapshot of the distribution of the drifters in the GDP. (A live tracking update of drifter locations is available through Google Earth at www.aoml.noaa.gov/phod/dac/gdp_maps.php.)

The Global Drifter Program (GDP) (formerly known as the Surface Velocity Program (SVP)) is the principal component of the Global Surface Drifting Buoy Array, a branch of NOAA's Global Ocean Observing System (GOOS)[1] and a scientific project of the Data Buoy Cooperation Panel (DBCP).[2][3] The project originated in February 1979 as part of the TOGA/Equatorial Pacific Ocean Circulation Experiment (EPOCS) and the first large-scale deployment of drifters was in 1988 with the goal of mapping the tropical Pacific Ocean's surface circulation.[4] The goal of the project is to use 1250 satellite-tracked surface drifting buoys to meet the need for an accurate and globally dense set of in-situ observations of mixed layer currents, sea surface temperature, atmospheric pressure, winds and salinity, as well as create a system to process this amount of data.[3] The GDP program is also important because the horizontal transports in the oceanic mixed layer are relevant to biological and chemical processes[5]

Drifters

This is a picture of the drifters used in the GDP (photo by GDP).

Drifters began being deployed for the SVP project in 1979 and the current design was developed from 1979 to 1992 until the current design was created.[4] The drifters are spherical surface buoys with a nylon drogue attached that allows for them to track the horizontal motion of water at an optimum depth of 15 m.[5] One known source of error is the drogue breaking and the wind speed having more of an influence on the buoy.[5] A tether strain gauge has been added to monitor tension of the buoy-drogue connection to resolve this issue.[5] The original drifters are heavy, bulky (40 cm diameter), and expensive relative to the newer "mini" drifters that are smaller, (30.5 cm diameter) cheaper, and lighter because the hull went from being made of 3 mm thick fiberglass to a less expensive Acrylonitrile-Butadiene-Styrene (ABC) plastic.[4] The surface float contains batteries, satellite transmitters, thermistor for sub-skin sea surface temperature, as well as other instruments that could be useful in measuring pressure, wind speed and direction and salinity.[4] The drifters are deployed from research vessels, volunteer ships, and through air deployment.[4] The drifters transmit samples every 90 seconds, but are capable of transmitting every 45 seconds and have an average lifetime of ~485 days in 2001.[4] Presently, there has been enough data gathered to observe currents at a resolution of 1 degree.[4] Single drifters can be tracked with the name of the drifter.

Success of the Program

The data from the GDP has been used for oceanographers to derive maps of the lateral diffusivity and Lagrangian scales of velocity, length and time across the whole Pacific.[6] It has also been used to observe the amount of plastic accumulation in the North Atlantic and Caribbean Sea from 1986 to 2008 and the impact that the plastic increase is having on the environment in the open ocean.[7] Climatologists have used this open ocean data to create models that are able to produce model equatorial ocean currents comparable to observations based on this data that was not available before.[8] These are samples of the most influential papers from a variety of fields, but the abundance of data over the extended amount of time that this project (and its predecessors) was able to produce have led to hundreds of other papers in these fields as well.

Nobel Laureate Desmond Tutu and Captain Jeremy Kingston deploy a drifter off of the coast of South Africa in the Semester at Sea program, where students from the Congressional School of Virginia and Elsies River High School in South Africa adopted the drifter and will be tracking its passage through the South Atlantic.[9]

Collaborators

The GDP is collaborating with private industries who build the drifters with accurate specifications.[3] The GDP is also coordinating with the NOAA's Atlantic Oceanographic and Meteorological Laboratory (AOML), who manages deployments, processes and archives the data, maintains META files describing each drifter deployed, develops and distributes data-based products, and updates the GDP website.[3] The NOAA's Joint Institute for Marine Observations (JIMO) is also involved, which supervises the industry, upgrades the technology, purchases drifters, and develops enhanced data sets.[3] There are contributing partners from Argentina, Australia, Brazil, Canada, France, India, Italy, Republic of Korea, Mexico, New Zealand, South Africa, Spain, United Kingdom, and the United States.[3]

See also

References

  1. ↑ Global Ocean Observing System (GOOS)
  2. ↑ Data Buoy Cooperation Panel (DBCP)
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 http://www.aoml.noaa.gov/phod/dac/gdp_objectives.php
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Lumpkin, R. and M. Pazos, 2006: Measuring surface currents with Surface Velocity Program drifters: the instrument, its data, and some recent results. Chapter two of Lagrangian Analysis and Prediction of Coastal and Ocean Dynamics (LAPCOD) ed. A. Griffa, A. D. Kirwan, A. J. Mariano, T. Ozgokmen, and T. Rossby.
  5. ↑ 5.0 5.1 5.2 5.3 Grodsky, Semyon A., Rick Lumpkin, and James A. Carton. "Spurious trends in global surface drifter currents." Geophysical Research Letters 38.10 (2011).
  6. ↑ Zhurbas, Victor, and Im Sang Oh. "Lateral diffusivity and Lagrangian scales in the Pacific Ocean as derived from drifter data." Journal of Geophysical Research: Oceans (1978–2012) 108.C5 (2003).
  7. ↑ Law, Kara Lavender, et al. "Plastic accumulation in the North Atlantic subtropical gyre." Science 329.5996 (2010): 1185-1188.
  8. ↑ Large, William G., et al. "Equatorial circulation of a global ocean climate model with anisotropic horizontal viscosity." Journal of Physical Oceanography 31.2 (2001): 518-536.
  9. ↑ http://www.aoml.noaa.gov/phod/dac/index.php