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Currents and Sediment Movement in Monterey Canyon

M. A. Noble, K. Kinoshita, L. Rosenfeld, C. Pilskaln, F. Schwing and S. Eittreim

Moorings were deployed for a year in Monterey Canyon across 1) a narrow part of the canyon (axis depth 1450 m), 2) a wider part (axis depth 2837 m), and 3) where the canyon cuts across the fan (axis depth 3223 m). Each mooring had current meters, transmissometers and sediment traps. The currents were mainly tidal, with the largest speeds observed near the bed. Tides in the narrow part were 4 times larger than at wider sections. A 3-day oscillation seen at most sites had large spatial scales. It was coherent across the canyon and from the shallowest to the deepest sites (horizontal separation 75 km). A sediment trap deployed 80 m off the bed into the narrow axis showed large particulate fluxes, 22-60 grams per square meter per day, and overflowed after 3 months. Subsequently, a very large turbidity event occurred that lasted 1 week. In 4 hours, the water column went from clear to very cloudy, the pressure changed and the water became slightly warmer and fresher. A large amount of material either slumped off the canyon walls or came down the canyon as a turbidity current.


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