Microstructure observations of turbulent heat fluxes in a warm-core Canada Basin eddy

TitleMicrostructure observations of turbulent heat fluxes in a warm-core Canada Basin eddy
Publication TypeJournal Article
Year of Publication2018
AuthorsFine E.C, MacKinnon JA, Alford MH, Mickett J.B
JournalJournal of Physical Oceanography
Date Published2018/10
Type of ArticleArticle
ISBN Number0022-3670
Accession NumberWOS:000446819000002
KeywordsAnticyclones; Arctic; arctic-ocean; Beaufort Sea; Diapycnal mixing; double-diffusive intrusions; eddies; inertial; internal waves; kinetic-energy dissipation; mediterranean salt lens; Mixing; observations; oceanography; pacific water; sea-ice; Ship; thermohaline steps; wave-propagation

An intrahalocline eddy was observed on the Chukchi slope in September of 2015 using both towed CTD and microstructure temperature and shear sections. The core of the eddy was 6 degrees C, significantly warmer than the surrounding -1 degrees C water and far exceeding typical temperatures of warm-core Arctic eddies. Microstructure sections indicated that outside of the eddy the rate of dissipation of turbulent kinetic energy epsilon was quite low . Three different processes were associated with elevated epsilon. Double-diffusive steps were found at the eddy's top edge and were associated with an upward heat flux of 5 W m(-2). At the bottom edge of the eddy, shear-driven mixing played a modest role, generating a heat flux of approximately 0.5 W m(-2) downward. Along the sides of the eddy, density-compensated thermohaline intrusions transported heat laterally out of the eddy, with a horizontal heat flux of 2000 W m(-2). Integrating these fluxes over an idealized approximation of the eddy's shape, we estimate that the net heat transport due to thermohaline intrusions along the eddy flanks was 2 GW, while the double-diffusive flux above the eddy was 0.4 GW. Shear-driven mixing at the bottom of the eddy accounted for only 0.04 GW. If these processes continued indefinitely at the same rate, the estimated life-span would be 1-2 years. Such eddies may be an important mechanism for the transport of Pacific-origin heat, freshwater, and nutrients into the Canada Basin.

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