PHYSICAL STRUCTURE AND TEMPORAL EVOLUTION OF GULF-STREAM WARM-CORE RING 82B

The hydrographic properties of warm-core ring 82B are shown from three cruises; April, June and August 1982. The velocity field for each cruise is formed from the gradient-current relationship, the observed hydrography, and the near surface flow as measured by a ship-mounted Acoustic Doppler Current Profiler. The data for each cruise were sorted into radial bins 15-km apart, and into vertical bins based on potential density. The changes in salinity on isopycnals from April to June 1982 were modelled as being due to radial advection, and both diapycnal and isopycnal mixing processes. The diffusivities in the pycnocline were found from a least-squares fit to the data. Most of the observed changes in salinity were explained with a constant vertical diffusivity (0.53 x 10(-4) m2 s-1), while the required lateral diffusivity was only 26.5 m2 s-1 at ring center, decaying to zero at a radius of 40 km.