A downslope propagating thermal front over the continental slope
van Haren, H.; Hosegood, P.J. (2017). A downslope propagating thermal front over the continental slope. Journal of Geophysical Research-Oceans 122(4): 3191-3199. https://dx.doi.org/10.1002/2017jc012797
In: Journal of Geophysical Research-Oceans. AMER GEOPHYSICAL UNION: Washington. ISSN 2169-9275; e-ISSN 2169-9291, more
In the ocean, internal frontal bores above sloping topography have many appearances,depending on the local density stratification, and on the angle and source of generation of the carrier wave.However, their common characteristics are a backward breaking wave, strong sediment resuspension, andrelatively cool (denser) water moving more or less upslope underneath warm (less dense) water. In thispaper, we present a rare example of a downslope moving front of cold water moving over near-bottomwarm water. Large backscatter is observed in the downslope moving front’s trailing edge, rather than theleading edge as is common in upslope moving fronts. Time series observations have been made during afortnight in summer, using a 101 m long array of high-resolution temperature sensors moored with anacoustic Doppler current profiler at 396 m depth in near-homogeneous waters, near a small canyon in thecontinental slope off the Malin shelf (West-Scotland, UK). Occurring between fronts that propagate upslopewith tidal periodicity, the rare downslope propagating one resembles a gravity current and includes strongconvective turbulence coming from the interior rather than the more usual frictionally generated turbulencearising from interaction with the seabed. Its turbulence is 3–10 times larger than that of more commonupslope propagating fronts. As the main turbulence is in the interior with a thin stratified layer close tothe bottom, little sediment is resuspended by a downslope propagating front. The downslope propagatingfront is suggested to be generated by oblique propagation of internal (tidal) waves and flow over a nearbyupstream promontory.
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