Gliding in the sea

Image of the Month - August 2009

Dynamic height along Jason-1 & 2 track (left, in cm), map of dynamic height and geostrophic velocities (right, top, in cm/s) and vertical velocity (right, bottom, in m/day), at 75 m depth, reconstructed from altimetry (black line) and gliders (purple line) in July 2008. The vertical velocity is blue for downard motion, red for upward. (Credits IMEDEA)
A glider (Credits E. Vidal Vijande)

Gliders are relatively new ocean-measuring devices. Autonomous underwater vehicles, they glide in the waters with a payload of instruments onboard, measuring all the while temperature, salinity, currents, chlorophyll, pressure... Such instruments are typically presented as complementary to satellites - they are measuring underwater, where the satellites can't, but locally, when the satellites give global coverage (satellite altimetry, however, is a bit special among the space measurements, since it depends on what is in the whole water column, from top to bottom).

Thus, mixing altimetry and glider data can provide information not available with either one separately, for example about the way waters are moving vertically.

See also: