Assessing the energetic interactions of subtidal flow on the continental slope in an Eastern boundary region

• Main Author: Tisch, Timothy Daniel
• Other Authors: Ramp, Steven R.
• Language: en_US
• Published: Monterey, California. Naval Postgraduate School 2012
• Online Access: http://hdl.handle.net/10945/23821

Approved for public release; distribution is unlimited === Seventeen-month time series (May 1989 - October 1990) of current, temperature and conductivity were obtained from 100, 300 and 500 m depth at site P2, located on the 800 m isobaths off Point Sur, and one-year time series (May 1990 - May 1991) of the same variables at similar depths were obtained from site P3, approximately 25 km father offshore on the 1800 m isobath. Results show that no net growth or decay of eddy potential energy (EPE) occurred at wither mooring during their respective deployment periods. At mooring P2, baroclinic instabilities within the water column were signaled by downgradient horizontal eddy heat fluxes that converted mean potential energy (MPE) to EPE at both 225 and 425 m. The dominant balance at 225 m was between mean flow advection (source) and upward eddy heat fluxes (EPE to eddy kinetic energy, EKE), with additional losses coming from downstream advection by the eddy flow. At 425 m, the dominant balance was between downgradient eddy heat fluxes (source) and downstream advection by eddy flow (sink). Unlike 225 m, vertical eddy heat fluxes at 425 m were a weak source (EKE to EPE) while mean flow advection was negligible. At P3, the net balance involved only downward eddy heat fluxes (source) and downstream advection by eddy flow (sink), as mean advection and MPE-EPE conversions were negligible. Analysis of energetic events within the time series of terms in the EPE equation did not reveal any canonical or common pattern which would explain the temporal means described above, but suggest the flow in this region is highly variable. In fact, most events magnitudes of terms were anywhere from 1o to 200 times that of the associated temporal mean. Events at P2 involved both horizontal and vertical processes and had longer time scales (several days to weeks) compared to those at P3, which had much shorter time scales and appeared to involve vertical processes only.