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• 1. [Article] Statistical properties of near surface currents in the California coastal transition zone

  During the summers of 1987 and 1988, 77 near-surface satellite-tracked drifters were deployed in or near cold filaments near Point Arena, California (39ºN), and tracked for up to 6 months as part of the ...

  Citation × Citation Citation Abstract Copy Title: Statistical properties of near surface currents in the California coastal transition zone Author: Beardsley, R. C., Abbott, Mark R., Stanton, T., Stuart, D., Ramp, S., Brink, K. H., Niiler, Pearn P., Huyer, Adriana, 1945- During the summers of 1987 and 1988, 77 near-surface satellite-tracked drifters were deployed in or near cold filaments near Point Arena, California (39ºN), and tracked for up to 6 months as part of the Coastal Transition Zone (CTZ) program. The drifters had large drogues centered at 15 m, and the resulting drifter trajectory data set has been analyzed in terms of its Eulerian and Lagrangian statistics. The CTZ drifter results show that the California Current can be characterized in summer and fall as a meandering coherent jet which on average flows southward to at least 30ºN, the southern end of the study domain. From 39ºN south to about 33ºN, the typical core velocities are of O(300 km) and the current meanders have alongshore wavelengths of O(100–200 km) and onshore-offshore amplitude of O(100–200 km). The lateral movement of this jet leads to large eddy kinetic energies and large eddy diffusivities, especially north of 36ºN. The initial onshore-offshore component of diffusivity is always greater than the alongshore component in the study domain, but at the southern end, the eddy diffusivity is more isotropic, with scalar single particle diffusivity (Kxx + Kyy) of O(8 x 107 cm2 s-1). The eddy diffusivity increases with increasing eddy energy. Finally, a simple volume budget for the 1988 filament observed near 37ºN off Point Arena suggests that subduction can occur in a filament at an average rate of O(10 m d-1) some 200 km offshore, thus allowing the cold water initially in the filament core to sink below the warmer ambient water by the time the surface velocity core has turned back onshore. This process explains why satellite temperature and color imagery tend to “see” only flow proceeding offshore. Title: Statistical properties of near surface currents in the California coastal transition zone Author: Beardsley, R. C., Abbott, Mark R., Stanton, T., Stuart, D., Ramp, S., Brink, K. H., Niiler, Pearn P., Huyer, Adriana, 1945- During the summers of 1987 and 1988, 77 near-surface satellite-tracked drifters were deployed in or near cold filaments near Point Arena, California (39ºN), and tracked for up to 6 months as part of the Coastal Transition Zone (CTZ) program. The drifters had large drogues centered at 15 m, and the resulting drifter trajectory data set has been analyzed in terms of its Eulerian and Lagrangian statistics. The CTZ drifter results show that the California Current can be characterized in summer and fall as a meandering coherent jet which on average flows southward to at least 30ºN, the southern end of the study domain. From 39ºN south to about 33ºN, the typical core velocities are of O(300 km) and the current meanders have alongshore wavelengths of O(100–200 km) and onshore-offshore amplitude of O(100–200 km). The lateral movement of this jet leads to large eddy kinetic energies and large eddy diffusivities, especially north of 36ºN. The initial onshore-offshore component of diffusivity is always greater than the alongshore component in the study domain, but at the southern end, the eddy diffusivity is more isotropic, with scalar single particle diffusivity (Kxx + Kyy) of O(8 x 107 cm2 s-1). The eddy diffusivity increases with increasing eddy energy. Finally, a simple volume budget for the 1988 filament observed near 37ºN off Point Arena suggests that subduction can occur in a filament at an average rate of O(10 m d-1) some 200 km offshore, thus allowing the cold water initially in the filament core to sink below the warmer ambient water by the time the surface velocity core has turned back onshore. This process explains why satellite temperature and color imagery tend to “see” only flow proceeding offshore. Close

• 2. [Article] The nature of the cold filaments in the California current system

  Data from the Coastal Transition Zone (CTZ) experiment are used to describe the velocity fields and water properties associate with cold filaments in the California Current. Combined with previous field ...

  Citation × Citation Citation Abstract Copy Title: The nature of the cold filaments in the California current system Author: Mackas, D. L., Swenson, M., Chavez, F., James, C., Batteen, M., Strub, P. Ted, Kadko, D., Abbott, Mark R., Hayward, T., Dewey, R., Ramp, S., Brink, K. H., Niiler, Pearn P., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Haidvogel, D., Barber, R., Haney, R., Walstad, L., Hood, R. R., Barth, John A., Washburn, L. A. Data from the Coastal Transition Zone (CTZ) experiment are used to describe the velocity fields and water properties associate with cold filaments in the California Current. Combined with previous field surveys and satellite imagery, these show seasonal variability with maximum dynamic height ranges and velocities in summer and minimum values in late winter and early spring. North of Point Arenda (between 39ºN and 42ºN) in spring–summer the flow field on the outer edge of the cold water has the character of a meandering jet, carrying fresh, nutrient-poor water from farther north on its offshore side and cold, salty, nutrient-rich water on its inshore side. At Point Arena in midsummer, the jet often flows offshore and continues south without meandering back onshore as strongly as it does farther north. The flow field south of Point Arena in summer takes on more of the character of a field of mesoscale eddies, although the meandering jet from the north continues to be identifiable. The conceptual model for the May–July period between 36ºN and 42ºN is thus of a surface jet that meanders through and interacts with a field of eddies; the eddies are more dominant south of 39ºN, where the jet broadens and where multiple jets and filaments are often present. At the surface, the jet often separates biological communities and may appear as a barrier to cross-jet transport, especially north of Point Arena early in the season (March–May) However, phytoplankton pigment and nutrients are carried on the inshore flank of the jet, and pigment maxima are sometimes found in the core of the jet. The biological effect of the jet is to define a convoluted, 100 to 400-km-wide region next to the coast, within which much of the richer water is contained, and also to carry some of that richer water offshore in meanders along the outer edge of that region. Title: The nature of the cold filaments in the California current system Author: Mackas, D. L., Swenson, M., Chavez, F., James, C., Batteen, M., Strub, P. Ted, Kadko, D., Abbott, Mark R., Hayward, T., Dewey, R., Ramp, S., Brink, K. H., Niiler, Pearn P., Huyer, Adriana, 1945-, Kosro, P. Michael, 1951-, Haidvogel, D., Barber, R., Haney, R., Walstad, L., Hood, R. R., Barth, John A., Washburn, L. A. Data from the Coastal Transition Zone (CTZ) experiment are used to describe the velocity fields and water properties associate with cold filaments in the California Current. Combined with previous field surveys and satellite imagery, these show seasonal variability with maximum dynamic height ranges and velocities in summer and minimum values in late winter and early spring. North of Point Arenda (between 39ºN and 42ºN) in spring–summer the flow field on the outer edge of the cold water has the character of a meandering jet, carrying fresh, nutrient-poor water from farther north on its offshore side and cold, salty, nutrient-rich water on its inshore side. At Point Arena in midsummer, the jet often flows offshore and continues south without meandering back onshore as strongly as it does farther north. The flow field south of Point Arena in summer takes on more of the character of a field of mesoscale eddies, although the meandering jet from the north continues to be identifiable. The conceptual model for the May–July period between 36ºN and 42ºN is thus of a surface jet that meanders through and interacts with a field of eddies; the eddies are more dominant south of 39ºN, where the jet broadens and where multiple jets and filaments are often present. At the surface, the jet often separates biological communities and may appear as a barrier to cross-jet transport, especially north of Point Arena early in the season (March–May) However, phytoplankton pigment and nutrients are carried on the inshore flank of the jet, and pigment maxima are sometimes found in the core of the jet. The biological effect of the jet is to define a convoluted, 100 to 400-km-wide region next to the coast, within which much of the richer water is contained, and also to carry some of that richer water offshore in meanders along the outer edge of that region. Close