Dense Water Overflows and Cascades

• Main Author: H. C. Mansley
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2014
• Subjects: Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.224.7299; http://www.reading.ac.uk/web/FILES/maths/helen_mansley.pdf

This study reviews our current knowledge of the main physical processes affecting the dynamics and properties of dense water overflows and cascades in the ocean. Dense water formed by cooling, evaporation or sea-ice formation in the surface layer of the ocean descends into a deep ocean basin over sloping topography as an overflow or cascade. Large-scale overflows provide substantial contributions to globally important water masses that ventilate the abyssal ocean and force the global meridional overturning circulation. Our understanding of dense water overflows is far from comprehensive due a lack of observations and the complexity of their dynamics. Problems with resolution, mixing and bottom drag, and subsequent model dependence on simple parameterisations, lead to highly unrealistic representation of overflows in current ocean circulation and climate models. Dense bottom flows descend under a balance of gravity, the Earth’s rotation, bottom friction and turbulent entrainment. Overflows and cascades are predominantly in geostrophic balance and flow primarily alongslope with a small downslope component and viscous drainage in the bottom boundary layer. The