Vertical mixing at intermediate depths in the Arctic boundary current

Lenn, Y. D., Wiles, P.J., Torres-Valdes, S., Abrahamsen, E.P., Rippeth, T.P., Simpson, J.H., Bacon, S., Laxon, S. W., Polyakov, I., Ivanov, V. and Kirillov, S. (2009) Vertical mixing at intermediate depths in the Arctic boundary current. Geophysical Research Letters, 36, L05601. (doi:10.1029/2008GL036792).

Abstract

Microstructure and hydrographic observations, during September 2007 in the boundary current on the East Siberian continental slope, document upper ocean stratification and along-stream water mass changes. A thin warm surface layer overrides a shallow halocline characterized by a ?40-m thick temperature minimum layer beginning at ?30 m depth. Below the halocline, well-defined thermohaline diffusive staircases extended downwards to warm Atlantic Water intrusions found at 200–800 m depth. Observed turbulent eddy kinetic energy dissipations are extremely low ( < 10?6 W m?3), such that double diffusive convection dominates the vertical mixing in the upper-ocean. The diffusive convection heat fluxes F H dc ?1 W m?2, are an order of magnitude too small to account for the observed along-stream cooling of the boundary current. Our results implicate circulation patterns and the influence of shelf waters in the evolution of the boundary current waters.

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