In the past decade, several large programs that monitor currents and transport patterns for periods from a few months to a few years were conducted by a consortium of university, federal, state, and municipal agencies in the central Southern California Bight, a heavily urbanized section of the coastal ocean off the west coast of the United States encompassing Santa Monica Bay, San Pedro Bay, and the Palos Verdes shelf. These programs were designed in part to determine how alongshelf and cross-shelf currents move sediments, pollutants, and suspended material through the region. Analysis of the data sets showed that the current patterns in this portion of the Bight have distinct changes in frequency and amplitude with location, in part because the topography of the shelf and upper slope varies rapidly over small spatial scales. However, because the mean, subtidal, and tidal-current patterns in any particular location were reasonably stable with time, one could determine a regional pattern for these current fields in the central Southern California Bight even though measurements at the various locations were obtained at different times. In particular, because the mean near-surface flows over the San Pedro and Palos Verdes shelves are divergent, near-surface waters from the upper slope tend to carry suspended material onto the shelf in the northwestern portion of San Pedro Bay. Water and suspended material are also carried off the shelf by the mean and subtidal flow fields in places where the orientation of the shelf break changes abruptly. The barotropic tidal currents in the central Southern California Bight flow primarily alongshore, but they have pronounced amplitude variations over relatively small changes in alongshelf location that are not totally predicted by numerical tidal models. Nonlinear internal tides and internal bores at tidal frequencies are oriented more across the shelf. They do not have a uniform transport direction, since they move fine sediment from the shelf to the slope in Santa Monica Bay, but carry suspended material from the mid-shelf to the beach in San Pedro Bay. It is clear that there are a large variety of processes that transport sediments and contaminants along and across the shelf in the central Southern California Bight. However, because these processes have a variety of frequencies and relatively small spatial scales, the dominant transport processes tend to be localized and have dissimilar characteristics even in adjacent regions of this small part of the coastal ocean.

Abstract Recent deepwater current observations in the Gulf of Mexico suggest this environment is more energetic than previously observed. Data and modeling results suggest that the Gulf of Mexico behaves as a two-layer system. Coupling of waters above 1,000 m to waters below is still unresolved and remains a topic of further research. The upper layer circulation is dominated by the Loop Current (LC), Loop Current rings (LCR), and smaller scale eddies. Recent data reveal a rich field of eddies of 30–150 km diameters that influence the LCR and shelf-edge currents. The lower layer circulation is less understood. Currents of ~30 cm/s vertically unchanged below 1,000 m, but showing near-bottom intensification interpreted as topographic Rossby waves (TRW) are reported. These waves have 20–30 day periods, wavelengths of 150–250 km, and propagate westward at about 9 km/day. Recent current measurements at 2,000 m reveal even stronger speeds (~90 cm/s) 11 m above the bottom and a small vertical shear below 1,000 m typical of TRW with periods of ~10 days and wavelengths of 70 km. In this lower layer, models show the presence of deep cyclone-anticyclone pairs that move westward and interact with the bottom topography, creating intense bottom currents. Direct observations of large furrows, active at present, suggest strong (~100 cm/s) near-bottom currents. The role of steep slopes in the generation of large amplitude TRW’s is at present unknown. It is also unknown if the observed strong ocean currents are responsible for the large furrows at the sea floor.