The UH Currents Group within SOEST (School of Ocean and Earth Science and Technology) at the University of Hawaii specializes in ocean current measurements, primarily using shipboard ADCPs (Acoustic Doppler Current Profilers). We
use it to acquire, process, and serve datasets;
provide services to the international oceanographic community;
and conduct research.
Firing et al. (2012) give a brief description of shipboard ADCP systems and UHDAS.
Ocean currents are a complex and ever-changing. In most of the world's oceans the long-term mean current is weak compared to the fluctuations, which arise from a combination of eddies and waves of many types. For example, satellite-tracked near-surface drifters near Hawaii can be seen going in all directions, often with looping trajectories characteristic of strong mesoscale eddies.
There are many ways of measuring ocean currents in addition to the drifter method illustrated above. Profilers measure the structure of currents as they vary with depth; the most common type of current profiler is the ADCP, also known as Doppler sonar. ADCPs can be deployed on the sea floor, on moorings, and from ships, either lowered with other instruments on a hydrographic wire (Lowered ADCP) or permanently mounted on the ship's hull (Shipboard ADCP). Most of our work is with this last deployment method.
Shipboard ADCPs can measure ocean current profiles from just below the ship to as much as 1600 m deep for the lowest-frequency instruments, the Teledyne-RDI Ocean Surveyor (OS38) operating at 38 kHz. The more common 75 kHz instrument (OS75) has higher vertical resolution but roughly half the range of the OS38.
As an example of ocean current measurements from a shipboard ADCP, here is a view of the upper-ocean current in the northwest Atlantic during a transit by the University of Rhode Island's R/V Endeavor in fall, 2011:
How do these currents vary with depth? To see that, we contour the velocity as a function of depth on the vertical axis and, for this example, longitude on the horizontal axis:
To be continued... This site is under construction.