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F-GEO-Naturvitenskap, geofag

Boundary layer processes affecting dense water flow on a slope

Tildelt: kr 1,3 mill.

Overflow at submarine ridges, and especially through channels is of the great importance for the global thermohaline circulation and interannual climate variability. Significant near-bottom mixing is usually observed within dense overflows from marginal s eas. These bottom-intensified currents commonly accelerate downslope, achieving supercritical Froude and Richardson numbers. Kelvin-Helmholtz instabilities and hydraulic jumps have been observed, resulting in significant entrainment and dilution of the so urce overflow waters. Dense bottom water in Storfjord is observed to drain continously over a 120 m deep sill at 77oN. The dynamic processes modifying the dense overflow in Storfjord will be studied using existing data as well as data which will be collected in August 2002. The methods include densely spaced hydrographic sections, ship-mounted ADCP and current moorings, i n addition to meteorological data from the region, and ice distribution from satellites. The proposed study will discuss a well-defined geophysical example of topographic flow, allowing detailed examination of the processes responsible for development and maintenance of a dense downflow in the vicinity of a sill. The measured velocity and den sity structure will serve as a framework for presentation and analysis of this dense flow.

Budsjettformål:

F-GEO-Naturvitenskap, geofag

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