Accession Number:

ADA277048

Title:

Submesoscale Dynamics near a Seamount. Part 1. Measurements of Ertel Vorticity

Descriptive Note:

Corporate Author:

WASHINGTON UNIV SEATTLE SCHOOL OF OCEANOGRAPHY

Personal Author(s):

Report Date:

1993-12-01

Pagination or Media Count:

22.0

Abstract:

The prevailing view that submesoscale fluctuations horizontal wavelengths less than a few kilometers and vertical wavelengths less than a few hundred meters are dominated by internal gravity waves is tested by measuring Ertels potential vorticity. Unlike geostrophic or nonlinear Ertel vorticity- carrying motions, internal waves have no Ertel vorticity fluctuations. Velocity and temperature profile surveys beside Ampere Seamount reveal appreciable Ertel enstrophy, and thus a significant non-internal-wave component, on horizontal wavelengths of 6-15 km and vertical wavelengths of 50-380 m. The twisting terms are negligible and the relative vorticities less than 0.2f, so the anomalies are in geostrophic balance. It is unlikely that the anomalies arise from stirring of the large-scale isopycnal gradients of stretching and planetary Ertel vorticity as this would require stirring lengths of thousands of kilometers. The most likely source appears to be forcing at the seamount, but generation by i dissipative 3D turbulence in the pycnocline or ii detrainment of the winter mixed layer cannot be absolutely ruled out. It remains to determine whether the coexistence of internal wave and Ertel vorticity-carrying fluctuations characterizes smaller scales lambda or 50 m, lambda sub H or 5 km. in the deep ocean away from topography as well

Subject Categories:

  • Physical and Dynamic Oceanography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE