Brief Statement of Upper Ocean Research Plans

Upper Ocean Workshop, held Timberline Lodge, Oregon-3-5 March 1980.Office of Naval ResearchContract N-00014-75-C-0502, Project NR 083 012, Reference M80-2

Evidence for interior dissipation and mixing during a coastal upwelling event off Oregon

During a strong, wind-driven, coastal upwelling event in July, 1973, off Oregon, large variations occurred in the properties of inertial-internal waves and water masses. At the peak of the event, the semidiurnal internal tide, which had significant amplitude during the spin-up phase, disappeared almost completely at mid-shelf. During the relaxation phase, near-inertial motions and anomalously warm water appeared at mid-depth in the upwelling zone...

Low-frequency variability in the Florida Current and relations to atmospheric forcing from 1972 to 1974

Two-year records of temperature and current from a single subsurface mooring are demonstrated to be representative of the fluctuation spectrum of the Florida Current for time scales of several days to one or more years. The dominant subinertial motions occur in three period bands: from 8 to 25 days, 4 to 5 days, and 2 to 3 days. Simultaneous observations in a crossstream array reveal energy maxima in the same bands for all locations...

Diagnoses of Simulated Water-Mass Subduction/Formation/Transformation in the Japan/East Sea (JES)

The impacts of surface atmospheric forcing of different time-space scales on the simulation of water-mass formation and spreading of formed water are investigated by quantifying water-mass subduction/formation/transformation for the Japan/East Sea (JES). The Princeton Ocean Model (POM) was implemented for the JES (JES-POM) to simulate interannual, seasonal, and mesoscale variations in velocity and mass fields. Three sets of atmospheric flux data were used; (1) 6-h fluxes calculated from 6-h atmospheric variables (syn), (2) monthly means of 6-h fluxes (empm), and (3) fluxes calculated from monthly averaged atmospheric variables (mont). The mass exchange between the mixed layer and interior in the JES was diagnosed in terms of annual subduction rate (S-ann). Three areas of local maximum S-ann (\u3e 500 m/yr) occurred: area V (41-43 degrees N west of 137 degrees E), K (36-39 degrees N west of 132 degrees E), and KB (near Korea Bay). Area V corresponds to the flux center (i.e., maximum heat and momentum fluxes) described by Kawamura and Wu [1998. Formation mechanism of Japan Sea Proper Water in the flux center off Vladivostok. J. Geophys. Res. 103 (C10), 21611-21622] the subduction region suggested by Senjyu and Sudo [ 1994. The upper portion of the Japan Sea proper water: its source and circulation as deduced from isopycnal analysis. J. Oceanogr. 50, 663-690; 1996. Interannual variation of the upper portion of the Japan proper water and its probable cause. J. Oceanogr. 52, 72-42] and Yoshikawa et al. [ 1999. Formation and circulation processes of intermediate water in the Japan Sea. J. Phys. Oceanogr. 29 (8), 1701-1722], and the wintertime convection location identified by Seung and Yoon [1995. Some features of winter convection in the Japan Sea. J. Occanogr. 51, 61-73]. With monthly forcing (mont), there is no localized maximum value off Vladivostok, while with forcing influenced by synoptic events (monthly; empm and 6-h syn), either one or two localized areas with a high subduction rate occur with year-to-year variations. The presence of simulated dense surface water ( \u3e sigma(0) = 26.8) in the northern JES is due to the effects of synoptic events during winter months when large heat loss and strong wind stress associated with cold-air outbreaks and extratropical cyclones occur. The convection magnitudes as a result of air-sea interaction are 3.0, 4.0, and 6.0Sv for mont, empm, and syn, respectively. A net flux of mass front the interior to the mixed layer (entrainment) occurs in the density range between sigma(0) = 24.0 and sigma(0) = 26.2 for both empm (3.5Sv) and syn (3.0Sv) while it occurs in the density range between sigma(0) = 24.0 and sigma(0) = 25.8 for mont (2.8Sv). The diffusive fluxes across the winter mixed layer base are about 0.8. 1.0, and 1.4Sv for mont, empm, and syn, respectively, All undiagnosed eddy-induced turbulent mixing (the residual of the balance after removing discretization error) for syn is almost twice that tor the other two cases (mont and empm). These results indicate that without synoptic atmospheric forcing. the diagnostics using the numerical circulation model may significantly underestimate buoyancy loss at the Surface. and. hence, water-mass formation. its well as mixing and spreading of the formed water mass. (c) 2005 Elsevier Ltd. All rights reserved

Turbulent jets and eddies in the California Current and inferred cross-shore transports

The article of record as published may be found at https://doi.org/10.1126/science.223.4631.51The instantaneous California Current is seen to consist of intense meandering current filaments Uets) intermingled with synoptic-mesoscale eddies. These quasi-geostrophic jets entrain cold, upwelled coastal waters (md rapidly advect them far offshore; this behavior accounts for the elongated, cool surface features that are seen extending across the California Current region in satellite infrared imagery. The associated advective mechanism should provide significant cross-shore transports of heat, nutrients, biota, and pollutants. The dynamics of the current system should be crucially influenced by its highly variable structure

Oceanic Variability Off the Central California Coast

Mesoscale variability off the Central California coast is strongly influenced by coastal upwelling and related processes. Off Point Sur, there is significant space-time variability in oceanic properties over periods of days and distances of several tens of km. However, the internal density field, averaged over space (ca. 120km alongshore) and time (ca. 18 days), reveals the expected characteristics of a coastal upwelling regime, including an equatorward surface jet 25km to 40km offshore and weaker poleward flow below 150m and within 20km of the coast. Upper ocean circulation is strongly influenced by the bathymetry offshore to water depths of at least 1000m. Based on repeated horizontal grids of oceanographic stations, horizontal correlation scales for temperature are of the order of 30km in the upper 100m; hence, a horizontal sampling rate of ca. 10km is desirable. Vertical correlation scales for temperature are of the order of 100m; hence, a vertical sampling rate of ca. 10m is desirable. Similarly, there are indications of a temporal correlation scale of a few weeks; hence, a temporal sampling rate of ca. a few days is desirable. Empirical Orthogonal Functions (EOFs) in the cross-shore vertical plane suggest the influence of coastally-trapped motions within 40km of the coast, with an intense alongshore, near-surface, transient coastal jet located ca. 20km offshore. Sudden spring transitions to coastal upwelling conditions are often pronounced in coastal temperature records, and they may precede the offshore migration of the major upwelling front by at least a month or more. The spring transitions occur over a period of about a week. In 1980, the spring transition propagated poleward along the California coast at a speed of ca. 64km d−1. During spring and summer, movement of a coastal upwelling front, often located between 15km and 50km offshore, is a major contributor to cross-shore variability. The upwelling front meanders with an alongshore scale of about 80km, a time scale of 30 to 40 days, and an amplitude scale of 10km RMS, based on satellite infrared (IR) imagery. The along-shore mean position of the major upwelling front migrates offshore during spring and summer. Offshore displacement of the front may be caused by Ekman transport over periods of days-to-weeks, and by Rossby wave dispersion over longer periods. During summer, a time-dependent offshore scale based on Rossby wave dynamics was more appropriate than the baroclinic Rossby radius. Every three to four years, during 1971 through 1984, El Nino episodes produced interannual variability in coastal sea surface temperature (SST) off Central California. Most of the warming occured during fall and winter. El Nino episodes were often followed by major spring transitions. The recent 1982/1983 episode was 2 to 3°C warmer than the three previous episodes over the past 14 years, and its influence lasted almost twice as long.NPS Research FoundationPhysical Oceanography Programme of the Office of Naval Researc

Hydrographic data from the OPTOMA program: OPTOMA18, 31 October and 2 November 1985

Approved for public release; distribution unlimited.This report is for the research project "Ocean Prediction Through Observation, Modeling and Analysis" sponsored by the Physical Oceanography Program of the Office of Naval Research under Program Element 61153N.Two P3 flights comprising OPTOMA18 were undertaken on 31 October and 2 November 1985 to sample a subdomain of the California Current System. This report presents the hydrographic data, acquired by AXBT deployments, from the flights.Office of Naval ResearchN000146WR2402

Physical processes impacting passive particle dispersal in the Upper Florida Keys

Physical processes affecting the dispersion of passive particles (e.g., coral larvae, pollutants) in the Upper Florida Keys are investigated through in situ observations (acoustic Doppler current profilers and surface drifters) and numerical ocean circulation modeling (horizontal resolution: 800 m, vertical resolution: 0.1–1 m). During the study period in August 2006 (set to coincide with an annual coral spawning event), Lagrangian trajectories in the vicinity of the reef tract indicate that alongshelf advection was mainly poleward and due to the subtidal flow of the Florida Current, while cross-shelf advection was mainly onshore and due to wind-driven currents. Tidal currents resulted in predominantly alongshelf displacements, but did not contribute significantly to net passive particle transport on a weekly timescale. Typical advection distances were of the order of 10 to 50 km for pelagic durations of 1 week, with significant variability linked to geographical location. In contrast, the direction of transport from the offshore reefs remained essentially constant (i.e., potential dispersion pathways were limited). In addition, Lagrangian trajectories and progressive vector diagrams in the vicinity of the reef tract indicate that alongshelf variations in the cross-shelf velocity gradient associated with the FC are relatively weak on an alongshore scale of ca. 50 km. For August 2006, the highest particle concentrations typically occur inshore of the reef tract, thereby suggesting that onshore transport associated with wind-driven currents contributes significantly to the local retention of passive organisms (and other tracers) in the Upper Florida Keys. Overall, the results illustrate the necessity of conducting targeted in situ observations and numerical model predictions to quantify the physical processes affecting reef-scale advection, especially in an effort to understand local retention and dispersion mechanisms for larval marine organisms

Hydrodynamics and sediment transport in a southeast Florida tidal inlet

A three-dimensional ocean circulation model is used to investigate the hydrodynamics of a tidal inlet and deltas system in Southeast Florida, and to understand the consequences for suspended and bedload sediment transport patterns. The model reproduces observed tidal currents and provides insight about residual currents caused by spatial asymmetries in the inlet throat and tidal deltas during ebb and flood flows. A particle-tracking approach for suspended and bedload sediment transport is used to simulate deposition patterns for different particle sizes. The simulation results qualitatively correlate with the distribution of sediment characteristics within the tidal inlet and deltas system and demonstrate sensitivity to the choice of advection velocities (e.g., near-bottom versus depth-averaged) and regions of sediment origin. Furthermore, the distinction between suspended and bedload transport as a function of particle size indicates significant differences in deposition patterns and their potential connection to geomorphologic features of the tidal inlet and deltas system