Topographic enhancement of vertical turbulent mixing in the Southern Ocean
Topographic enhancement of vertical turbulent mixing in the Southern Ocean
Date
2017-03-06
Authors
Mashayek, Ali
Ferrari, Raffaele
Merrifield, Sophia T.
Ledwell, James R.
St. Laurent, Louis C.
Naveira Garabato, Alberto C.
Ferrari, Raffaele
Merrifield, Sophia T.
Ledwell, James R.
St. Laurent, Louis C.
Naveira Garabato, Alberto C.
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10.1038/ncomms14197
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Abstract
It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation.
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© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 8 (2017): 14197, doi:10.1038/ncomms14197.
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Nature Communications 8 (2017): 14197