Bathymetric influences of the Emperor Seamounts upon the subarctic gyre of the North Pacific: Examining boundary current dynamics along the eastern side of the mountain ridge with an idealized numerical model |
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| Authors: | Taku Wagawa Yutaka Yoshikawa Akira Masuda |
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| Institution: | (1) Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Kawaguchi, Saitama, 332-0012, Japan;(2) Center for Environmental Research, Ocean Research Institute, The University of Tokyo, Nakano-ku, Tokyo, 164-8639, Japan;(3) Division of Oceanic and Atmospheric Science, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810, Japan; |
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| Abstract: | The possible influences of the Emperor Seamounts (ESs) upon the subarctic gyre of the North Pacific (NPSAG) were investigated
by a series of numerical experiments. In the experiments, a two-layer ocean with a meridional mountain ridge was forced by
seasonally varying wind stress. We focused on how the return ratio, the ratio of the boundary transport along the eastern
side of the ridge to the interior Sverdrup transport, changes with ridge height, width and density stratification. It was
found that the return ratio can be large if the ridge width is greater than the width of the viscous boundary layer. In this
case, the bottom pressure torque determines the return ratio; the return ratio is almost proportional to the ridge height
when the ridge height is small and some contours of planetary potential vorticity pass over the ridge. However, the return
ratio is independent of the ridge height and decreases with the stratification when the ridge height is large and all the
contours of planetary potential vorticity are closed. These dependences of the return ratio were understood in terms of barotropic
and baroclinic components of the bottom pressure torque. Implications for the bathymetric influences of ESs on the actual
NPSAG are also discussed. |
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