Cross-shelf eddy heat transport in a wind-free coastal ocean undergoing winter time cooling

A steady state cross-shelf density gradient of a wind-free coastal ocean undergoing winter time cooling is found for cooling and geometries which do not vary in the along-shelf direction. The steady state cross-shelf density gradient exists even when the average density of the water continues to increase. The steady state density gradient dan be attained in less than a winter for parameters appropriate to the mid-Atlantic Eight. The cross-shelf eddy-driven buoyancy fluxes which cause this steady state gradient are found to depend critically on bottom friction and bottom slope, and the coastal polyna solutions of Chapman and Gawarkiewicz [1997] are significantly modified by this dependence in the limit of polynas with a large alongshore extent. Bottom friction retards the cross-shelf propagation of eddies, so that the buoyancy transport is no longer carried by self-advecting eddy pairs but mixed across the shelf by interacting eddies. The eddy interaction changes the length scale of the eddies until it is the lesser of the Rhines arrest scale or an analogous frictional arrest scale. The estimates of the steady state cross-shelf density gradient are found to compare well with numerical model results

Enhancement of wind-driven upwelling and downwelling by alongshore bathymetric variability

Steady wind-driven flow along a shelf of changing width is described with a frictional barotropic model valid in the limit of small Rossby and Burger number. In these limits, an alongshore wind drives enhanced onshelf transport in a coastal ocean if the shelf widens downwind, and the change in shelf width only affects the flow in the direction of Kelvin wave propagation ( downwave\u27\u27) from the change in shelf width. There is enhanced onshore transport of cold, nutrient-laden bottom water if the winds favor upwelling and the shelf narrows in the direction of Kelvin wave propagation. This enhanced transport extends a considerable distance away from the change in shelf width but becomes concentrated near the shelf break far from the change in width. Isobath curvature on the scale of the shelf width significantly modifies local cross-shelf transport. The cross-shelf transport of nutrient-rich water during upwelling is expected to be enhanced from Point Eugenia to La Jolla, San Luis Obispo to Monterey, and Point Reyes to Cape Mendocino on the west coast of North America

Remotely forced nearshore upwelling in southern California

[1] Alongshore winds in Baja California strongly influence nearshore temperatures hundreds of kilometers to the north at Point Loma, San Diego, California, on timescales of a week to a year. The time lag between wind and temperature is consistent with first mode coastal trapped wave phase speed. The nearshore cross-shelf circulation forced by the coastal trapped waves is, at least much of the year, oppositely directed at the surface and bottom. No relation is found between the winds and temperature for periods greater than a year. It is argued that similar results may be found elsewhere in the Southern California Bight. The relationship between stratification and bottom temperature varies over the 1.3 years of data, but for much of the time, warmer bottom waters are associated with even warmer surface waters and thus stronger stratification. The effects of the remotely forced cross-shelf exchange on coastal pollution, nutrient dynamics, and larval transport are briefly discussed

Syntheses of some alkylating agents with potential cytotoxic properties

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Dynamics of wind-driven upwelling and relaxation between Monterey Bay and Point Arena: Local-, regional-, and gyre-scale controls

In north and central California, equatorward winds drive equatorward flows and the upwelling of cold dense water over the shelf during the midspring and summer upwelling season. When the winds temporarily weaken, the upwelling flows between Point Reyes and Point Arena relax,\u27\u27 becoming strongly poleward over the shelf. Analytical and numerical models are used to describe the effect of alongshore variability of winds, bathymetry, and basin-scale pressure gradients on the strength of upwelling and its relaxation. Alongshore winds weaken to the south of Point Reyes, and the shelf becomes narrower from Point Reyes to Monterey Bay. Both of these lead to reduced upwelling at and to the north of Point Reyes, causing an alongshore gradient of temperature and density on the shelf. These alongshore gradients lead to an along-isobath pressure gradient over the shelf that drive the relaxation flows. A simple analytical model is used to explain the dynamics, magnitude, and structure of the relaxation flows. The modeling also suggests that the depth of origin of the upwelled waters, and thus their temperature, is controlled by the along-isobath pressure gradient that exists over the continental slope. This along-slope pressure gradient is also responsible for the California undercurrent in this region. This pressure gradient is not generated in a model of the Californian coast extending from 32 degrees N to 42 degrees N and integrated for several months, suggesting it is caused by dynamics whose spatial or temporal scales are larger than the Californian coast and/or longer than several months

Cooling and internal waves on the Continental Shelf

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 1998The evolution of a coastal ocean undergoing uniform surface heat loss is examined. The dynamics of this ocean are initially modulated by the intense vertical mixing driven by surface cooling. The strong vertical mixing prevents the formation of geostrophic flows and inhibits the cross-shelf flux of heat. The vertical mixing is eventually suppressed by the advective transport of cold, dense water offshore. Once this happens, alongshore geostrophic flows form, and become baroclinically unstable. The surface heat flux is then balanced by a cross-shelf eddy heat flux. Scales are found for the cross-shelf density gradient which results from this balance. Solutions for linear internal waves are found for a wedge-shaped bathymetry with bottom friction. Bottom friction is capable of entirely dissipating the waves before they reach the coast, and waves traveling obliquely offshore are reflected back to the coast from a caustic. The internal wave climate near two moorings of the Coastal Ocean Dynamics Experiment observation program is analyzed. The high frequency internal wave energy levels were elevated above the Garrett and Munk spectrum, and the spectrum becomes less red as one moves to the shore. The wave field is dominated by vertical-mode one waves, and internal wave energy propagates shoreward.This work was funded by an Office of Naval Research fellowship and and Office of Naval Research AASERT fellowship, N00014-95:-1-0746

The role of bacterial surface polymers in the adhesion of freshwater bacteria to solid surfaces

In the study of the mechanism of non-specific permanent adhesion of bacteria at the solid-liquid interface a number of alternative approaches have been used. These include; the use of thermodynamic models, to explain observations of biocontact phenomenal the use of disruptive chemicals, enzymes and electronnicroscopy to investigate the nature of the adhesive bond and finally the biochemical analysis of cell surface components possibly involved in the process. In this study all three approaches were combined in an investigation of the role of cell surface components on the attachment of freshwater organisms to solid surfaces. A thermodynamic relationship was found using attachment assays on a number of freshwater isolates emphasising the influence of water on the adhesive process. Further investigations of phenotypic changes in membrane surface composition of a number of Pseudomonas isolates using continuous culture demonstrated the involvement of polysaccharide in the inhibition of adhesion. A number of adhesion mutants were analysed for genotypic changes in outer membrane proteins, lipopolysaccharides and exopolysaccharides which also confirmed the inhibitory role of polysaccharides. The results demonstrate the role of cell surface characteristics in the adaptability of the organism to micro-environments such as a solid/liquid or air/liquid interface or the aqueous phase