HR: 0800h
AN: OS41A-0156    [Abstracts]
TI: Across-shore Eddy Transport off Central California
AU: * Margolina, T
EM: tmargoli@nps.edu
AF: Naval Postgraduate School, 833 Dyer Rd, Monterey, CA 93943, United States
AU: Collins, C A
EM: collins@nps.edu
AF: Naval Postgraduate School, 833 Dyer Rd, Monterey, CA 93943, United States
AU: Ivanov, L M
EM: lmivanov@nps.edu
AF: University of Southern California, 3551 Trousdale Pkwy., Los Angeles, CA 90089-1140, United States
AU: Rago, T A
EM: tarago@nps.edu
AF: Naval Postgraduate School, 833 Dyer Rd, Monterey, CA 93943, United States
AB: Kinematic characteristics and physical mechanisms of across-shore transport off Central California were studied using subsurface RAFOS data collected between 1992-2007 and the UCLA ROMS output for meso- and submesoscales. Kinematic characteristics of the transport, including translation speed and direction, period of rotation, and characteristic swirl velocity were estimated from the spectral analysis of RAFOS trajectories directly and from Lagrangian statistics computed using an exit time concept. Pair statistics of floats were also used to understand the physical mechanisms of the westward transport. RAFOS floats demonstrated two types of subsurface westward transport between 300 m and 375 m. First, intensive mesoscale eddies, as well as long-lived submesoscale coherent vortices with diameter of 30-40 km transported floats as far as 1200 km offshore. Data also show that some eddies retained floats for a year or longer. The transport seems to be of an advective type. The kinematic characteristics of the transport were extracted from the float trajectories using spectral and wavelet analysis. Second, other float trajectories were combinations of several irregular loops with rapid translations between them. This motion was interpreted in terms of traps and flights of two-dimensional turbulent motion, and was quantified using the exit time. The relative dispersion of floats followed the ballistic law up to 100 km distance between floats but was exponential when the distance was between 150 and 400 km. To understand the physical mechanisms of the westward transport, the ROMS output with spatial resolution of 3.5 km was used. The results showed that nonlinear interactions between coherent mesoscale eddies play an important role inshore as well as in the Coastal Transit Zone. ROMS demonstrated intensive eddy pairing and merging. Both these processes are a signature of upscale kinetic energy flux. We hypotheze that eddy pairing resulting in coherent eddy dipoles was one of the main factors contributing to RAFOS float dispersion.
UR: http://www.oc.nps.navy.mil/npsRAFOS/
DE: 4255 Numerical modeling (0545, 0560)
DE: 4516 Eastern boundary currents
DE: 4520 Eddies and mesoscale processes
DE: 4534 Hydrodynamic modeling
DE: 4568 Turbulence, diffusion, and mixing processes (4490)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting