30 Years of Drifter Data Allow Scientists to Create a Visual Climatology of Ocean Currents
Using over 30 years of observations from satellite-tracked surface drifting buoys, NOAA oceanographers derived a global climatology of seasonally-varying ocean surface currents at one-half degree resolution. This data set can be used to better understand how the ocean transports properties like heat, salt, and passive tracers, and as a reference to study changes in ocean currents over time.
The seasonal climatology is available on the AOML website, indicating near-surface currents and sea surface temperatures (SST's) for the world, at monthly and one-half degree resolution.
Satellite-tracked drifting buoys provide observations of near-surface circulation at unprecedented resolution. In September 2005, the Global Drifter Array became the first fully realized component of the Global Ocean Observing System when it reached an array size of 1250 drifters. A drifter is composed of a surface float which includes a transmitter to relay data and a thermometer that reads temperature a few centimeters below the air/sea interface. The surface float is tethered to a holey sock drogue, centered at 15 m depth. The drifter follows the surface current flow integrated over the drogue depth. Drifter velocities are derived from finite differences of their position fixes. These velocities, and the concurrent SST measurements, are archived at AOML's Drifting Buoy Data Assembly Center where the data are quality controlled and interpolated to 1/4-day intervals.