A study of the benthic boundary layer associated with the cold filament of the western North Atlantic

• Other Authors: Ezer, Tal., Florida State University
• Format: Text
• Language: English
• Published: 1989
• Subjects: Physical Oceanography; Geophysics; Physics; Atmospheric Science; Mellor; North Atlantic
• Online Access: https://diginole.lib.fsu.edu/islandora/object/fsu%3A77987/datastream/TN/view/A%20study%20of%20the%20benthic%20boundary%20layer%20associated%20with%20the%20cold%20filament%20of%20the%20western%20North%20Atlantic.jpg

The small-scale spatial variations of the Bottom Boundary Layer (BBL) associated with anomalous bottom layers in the form of cold eddies or cold filaments are studied here. Statistics of long term records from the HEBBLE area ($\sp\sim$40$\sp\circ$N, 62$\sp\circ$W), where the deep jet known as the Cold Filament (CF) is found, indicate a permanent benthic front, a few Rossby radii of deformation wide, with which are associated significant horizontal gradients of temperature and velocity. Empirical formulas are found for the parameterization of the eddy diffusivity, which fit the calculations of the level 2.5 scheme of Mellor and Yamada (1974, 1982). When they are used in a K-model (i.e., a model in which the eddy viscosity is calculated directly from the stratification and the velocity field), about 20% of the computational time can be saved compared to a second order turbulence closure model. A two dimensional (x-z) primitive equation model is used to study the interaction between the BBL and the CF under constant forcing conditions. The results of the numerical simulations are compared favorably to observations of temperature and velocity profiles. The major effect of the interaction process results from the cross isotherm flow associated with the Ekman veering in the BBL. In the left edge (looking down-stream) of the CF the intrusion of cold core water under warm interior water forms a very thin and stable BBL, while in the right edge the Ekman transport forms an unstable, thermally convective, region with large turbulence. The velocity profiles as well as the Ekman spirals in the vicinity of the CF show significant modification from the ones obtained by classical Ekman dynamics, mainly due to thermal wind effects associated with the CF. Source: Dissertation Abstracts International, Volume: 50-03, Section: B, page: 0890. Major Professor: Georges L. Weatherly. Thesis (Ph.D.)--The Florida State University, 1989.