Argo (oceanography)

Argo is an international programme for researching the ocean. It uses profiling floats to observe temperature, salinity and currents. Recently it has observed bio-optical properties in the Earth's oceans. It has been operating since the early 2000s. The real-time data it provides support climate and oceanographic research.^[1][2] A special research interest is to quantify the ocean heat content (OHC). The Argo fleet consists of almost 4000 drifting "Argo floats" (as profiling floats used by the Argo program are often called) deployed worldwide. Each float weighs 20–30 kg. In most cases probes drift at a depth of 1000 metres. Experts call this the parking depth. Every 10 days, by changing their buoyancy, they dive to a depth of 2000 metres and then move to the sea-surface. As they move they measure conductivity and temperature profiles as well as pressure. Scientists calculate salinity and density from these measurements. Seawater density is important in determining large-scale motions in the ocean.

Average current velocities at 1000 metres are directly measured by the distance and direction a float drifts while parked at that depth, which is determined by GPS or Argos system positions at the surface. The data is transmitted to shore via satellite, and is freely available to everyone, without restrictions.

The Argo program is named after the Greek mythical ship Argo to emphasize the complementary relationship of Argo with the Jason satellite altimeters. Both the standard Argo floats and the 4 satellites launched so far to monitor changing sea-level all operate on a 10-day duty cycle.