Mixing in Downslope Flows in the Ocean – Plumes versus Gravity Currents

• Main Author: Peter G. Baines
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2007
• Subjects: Ross Sea; Denmark Strait
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.612.5059; http://people.eng.unimelb.edu.au/pbaines/Baines(2008)DownslopeA_O.pdf

ABSTRACT The nature of downslope flows into stratified environments as revealed by laboratory experiments is described, and the results are then applied to interpret particular downslope flows into the ocean. In the labora-tory, non-rotating downslope flows can be divided into two main types: detraining gravity currents over suffi-ciently gentle slopes, where the buoyancy force of the dense downflow is mainly balanced by bottom drag, and entraining plumes over sufficiently steep slopes, where the buoyancy force is balanced by vigorous entrainment of environmental fluid from above. This mixing character of the flow is determined by the bottom slope, the drag coefficient and the buoyancy number B = QN3/G2, where Q and G are the volume flux and buoyancy of the down-flow and N is the buoyancy frequency of the environment. These experiments may be applied to situations in the ocean where the flow is in approximate geostrophic balance with its transverse pressure gradient, and the para-meters are applied to the flow path on the slope. Examples are provided for a number of downslope flows in var-ious locations, including the Red Sea outflow, the Mediterranean outflow into the Black Sea and the Atlantic, the Denmark Strait overflow and the outflow from the Ross Sea. RÉSUMÉ [Traduit par la rédaction] Nous décrivons la nature des écoulements descendants dans les environnements stratifiés en nous basant sur des expériences en laboratoire et nous nous servons ensuite des résultats pour interpréter certains écoulements descendants dans l’océan. Au laboratoire, on peut regrouper les