HR: 16:00h
AN: OS54B-01 INVITED     [Abstracts]
TI: SUBMESOSCALE COASTAL OCEAN SURFACE CURRENT VARIABILITY
AU: * Shay, L K
EM: nick@rsmas.miami.edu
AF: University of Miami/RSMAS (MPO&), 4600 Rickenbacker Causeway, Miami, FL 33149-1098 United States
AU: Peters, H
EM: hpeters@rsmas.miami.edu
AF: University of Miami/RSMAS (MPO&), 4600 Rickenbacker Causeway, Miami, FL 33149-1098 United States
AU: Cook, T
EM: tcook@rsmas.miami.edu
AF: University of Miami/RSMAS (MPO&), 4600 Rickenbacker Causeway, Miami, FL 33149-1098 United States
AU: Haus, B
EM: bhaus@rsmas.miami.edu
AF: University of Miami/RSMAS (MPO&), 4600 Rickenbacker Causeway, Miami, FL 33149-1098 United States
AU: Martinez, J
EM: lbowen@rsmas.miami.edu
AF: University of Miami/RSMAS (MPO&), 4600 Rickenbacker Causeway, Miami, FL 33149-1098 United States
AB: Measurements of coastal ocean surface currents using High Frequency (HF) radars with phased array technology have revealed a broad spectrum of processes. During a series of ONR-sponsored experiments, both HF (16 and 25 MHz) and Very High Frequency (VHF: 50 MHz) radars have revealed energetic, coherent submesoscale processes that are affected by mesoscale currents. Flowing along the coast of southeastern Florida shelf (EFS), the Florida Current (FC) produces an environment of large mean vorticity with embedded, energetic mesoscale and submesocale flow features. These submesoscale features, defined here as flow features with length scales less than the internal deformation radius of 10-40 km, have been observed with an Ocean Surface Current Radar (OSCR) and Wellen Radar (WERA). These features are energetic and coherent over scales of 2 to 20 km. With amplitudes of up to 50 cm s-1, we have limited knowledge of the spectrum of processes within the submesoscale band, of their nature, interaction with other flow scales and energy cascades. Observations in radar and sun glint photos from the space shuttle also indicate that submesoscale vortices and spiral eddies on the free surface are highly nonlinear with Rossby numbers ranging from 5 f to as high as 10 f . These spiral-like images of the surface fields represent a challenge from both fluid dynamical and remote sensing viewpoints as they have a pronounced impact on the surface roughness and backscattered energy. As part of the ONR sponsored SEA-COOS program, a three-station WERA is providing near-real time mapping of the surface velocity field at ~1 km resolution over a range of 100 to 120 km. Sampling intervals range from minutes to hours to help resolve the gradients and high frequency submesoscale motions where RMS differences have been in the 6 to 10 cm s-1 range. Unlike mesoscale features, which are elongated in the along-shelf direction, submesoscale processes tend to be more isotropic with considerable cross-shelf flow where large horizontal gradients in properties occur due to the interactions between fresher riverine, estuarine and shelf water. This property provides a potential for generating significant Reynolds stresses, u'v', a processes completely unexplored. The isotropic nature of submesoscale processes is also relevant with respect to turbulent mixing embedded in the flow, especially in the bottom boundary layer ``slippery boundary layer'' concept. The Florida Straits is an optimal regime to study the 3-D aspects of these energetic currents associated with coherent submesoscale variability.
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3384 Waves and tides
DE: 4512 Currents
DE: 4524 Fine structure and microstructure
DE: 4528 Fronts and jets
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting