Document Title

Buoyant Gravity Currents Released from Tropical Instability Waves

Department/School

Physics

Abstract

Two extremely sharp fronts with changes in sea surface temperature greater than 0.48 degrees Celsius over lateral distances of approximately 1 m were observed in the equatorial Pacific at 08, 140 degrees W and at 0.75 degrees N, 110 degrees W. In both cases, layers of relatively warm and fresh water extending to ;30-m depth propagated to the southwest as gravity currents. Turbulent kinetic energy dissipation rates averaging 4.5 x 10-6W kg-1 were measured with a microstructure profiler within the warm layer behind the leading edge of the fronts—1000 times greater than dissipation in the ambient water ahead of the fronts. From satellite images, these fronts were observed to propagate ahead of the trailing edge of a tropical instability wave (TIW) cold cusp. Results from an ocean model with 6-km grid resolution suggest that TIW fronts may release gravity currents through frontogenesis and loss of balance as the fronts approach the equator and the Coriolis parameter weakens. Sharp frontal features appear to be ubiquitous in the eastern tropical Pacific, have an influence on the distribution of biogeochemical tracers and organisms, and play a role in transferring energy out of the TIW field toward smaller scales and dissipation.

Document Type

Article

Publication Title

Journal of Physical Oceanography

Publication Date

2-14-2018

Volume

48

Issue

2

Pages

361-382

Digital Object Identifier (DOI)

10.1175/JPO-D-17-0144.1

Document Version

Publisher's version

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