Double-Diffusive Recipes. Part II: Layer-Merging Events
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Authors
Radko, T.
Flanagan, J.D.
Stellmach, S.
Timmermans, M.-L.
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2014-05
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Abstract
This study explores the dynamics of thermohaline staircases: well-defined stepped structures in temperature
and salinity profiles, commonly observed in regions of active double diffusion. The evolution of staircases
in time is frequently characterized by spontaneous layer-merging events. These phenomena, the authors
argue, are essential in regulating the equilibrium layer thickness in fully developed staircases. The pattern and
mechanics of merging events are explained using a combination of analytical considerations, direct numerical
simulations, and data analysis. The theoretical merger model is based on the stability analysis for a series of
identical steps and pertains to both forms of double diffusion: diffusive convection and salt fingering. The
conceptual significance of the proposed model lies in its ability to describe merging events without assuming
from the outset specific power laws for the vertical transport of heat and salt—the approach adopted by earlier
merging models. The analysis of direct numerical simulations indicates that merging models based on the
four-thirds flux laws offer adequate qualitative description of the evolutionary patterns but are less accurate
than models that do not rely on such laws. Specific examples considered in this paper include the evolution of
layers in the diffusive staircase in the Beaufort Gyre of the Arctic Ocean.
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The article of record as published may be found at http://dx.doi.org/10.1175/JPO-D-13-0156.1
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Oceanography
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Journal of Physical Oceanography, Volume 44, pp. 1285-1305, May 2014.
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.