Numerical Study of Formation of Dichothermal Water in the Bering Sea |
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| Authors: | Takahiro Miura Toshio Suga Kimio Hanawa |
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| Institution: | (1) Department of Geophysics, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan |
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| Abstract: | A one-dimensional numerical model with a level-2.5 turbulent closure scheme to provide vertical mixing coefficients has been
used to investigate the process by which the dichothermal water is formed in the Bering Sea, the density of which is about
26.6 sigma-theta. The water column to be simulated is assumed to move along a predetermined path. That is, the present model
is of the Lagrangian-type. Surface boundary conditions are given using the climatologies of heat, freshwater and momentum
fluxes. In order to obtain a plausible moving speed of the water column along the path, pre-liminary experiments were done
using the surface fluxes in the central part of the Bering Sea for the initial temperature and salinity profiles at the entrance
of the Sea. As a result, it was found that the temperature minimum layer, i.e., the dichothermal water with temperature similar
to the climatology at the exit of the Bering Sea, was formed after about two years of integration. Based on the result, the
movement speed of the water column along the path was set as 4.5 cm/s in the standard run. It was found that this model could
plausibly reproduce the subsurface temperature minimum layer. That is, the dichothermal water was formed in the winter mixed
layer process in the Bering Sea. The existence of the subsurface halocline (pycnocline) prohibited the deeper penetration
of the winter mixed layer, and therefore water with a temperature colder than that under the mixed layer was formed in the
mixed layer due to wintertime surface cooling. In the warming season this water remains as the subsurface temperature minimum
layer between the upper seasonal thermocline and the lower halocline.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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| Keywords: | Bering Sea dichothermal layer mixed layer numerical model heat flux |
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