R/V Seward Johnson Cruise 9908: Cruise Report and Preliminary Results
Abstract
Seawater moving through the Earth's magnetic field generates electric and magnetic fields. This phenomenon is often called motional induction. Previous studies have shown that these motional electric fields can be measured and interpreted in terms of the ocean's velocity field. This report presents results from tests of two instruments that observe motionally induced electric fields in the sea. One, the Towed Transport Meter (TTM), observes three orthogonal components of the ocean's electric field near the surface as a function of distance along track. These data and observations of the motion of the towing ship permit determination of the vertically averaged velocity of the whole water column. The TTM3 was towed in various patterns, such as reciprocal courses an boxes, to determine its performance. The second instrument, EM-POGO, combines electric field observations similar to those of the TTM3 with GPS navigation. This instrument profiles in the vertical and produces a profile of the absolute velocity of the ocean from the surface to the bottom or 200 m, whichever comes first. The resulting profile was compared with the velocity profile from the ship's acoustic Doppler current profiler (ADCP). The field tests were very useful. The TTM3 was found to be difficult to operate reliably, but the EM-POGO produced results in close agreement with those of the ADCP.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2000
- Accession Number
- ADA381489
Entities
People
- J.h. Dunlap
- M. D. Allison
- Thomas B. Sanford
Organizations
- University of Washington