A Satellites like TOPEX/POSEIDON collect data on ocean surface conditions along regularly repreated tracks taht cover the whole globe over a period of days.
B The ALACE (Autonomous Lagrangian Circulation Explorer) is a subsurface float that periodically adjusts its buoyancy to rise to the surface where it transmits its position to a communicatoin satellite. It then returns to depth to track flow for a period of weeks.
C An acoustic Doppler current porfiler uses sound waves to measure ocean current velocities while the ship is moving.
D A rosette holds 12 to 36 water-sample bottles. They are triggered to close at different depths so to collect water samples for analysis.
E RAFOS and SOFAR floats monitor water velocity by suing sound waves to fix their positions.
F An expendable bathythermograph is a free-fall probe that measures temperature in the water column.
G A moored current mater measures the speed and direction of water at a single location over time periods of about one year.
H Surface drifters track the motion of water in the upper 15 meters of the water column.
I Shore-based tide gauges record tidal heights in coastal zones. They also are used to calibrate satellite-derived sea-surface height measurements.
J Communications satellites receive data from instruments on land and at sea, then transmit them to ground stations where oceanographers begin the interpretation process.