Possible Density Change of the Origin of North Pacific Intermediate Water Due to Double Diffusion in the Mixed Water Region |
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| Authors: | Email author" target="_blank">Ryuichiro?InoueEmail author Jiro?Yoshida |
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| Institution: | (1) Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Konan, Minato-ku, Tokyo 108-8477, Japan;(2) Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, BC, V8W-3P6, Canada |
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| Abstract: | In this study we test Talley's hypothesis that Oyashio winter mixed-layer water (26.5–26.6σ θ) increases its density to produce the North Pacific Intermediate Water (NPIW) salinity minimum (26.7– 26.8σθ) in the Mixed Water Region, assuming a combination of cabbeling and double diffusion. The possible density change of Oyashio
winter mixed-layer water is discussed using an instantaneous ratio of the change of temperature and salinity along any particular
intrusion (R
l
). We estimate the range of R
l
DD
required to convert Oyashio winter mixed-layer water to the NPIW salinity minimum due to double diffusion, and then assume
double-diffusive intrusions as this conversion mechanism. A double-diffusive intrusion model is used to estimate R
l
DD
in a situation where salt fingering dominates vertical mixing, as well as to determine whether Oyashio winter mixed-layer
water can become the NPIW salinity minimum. Possible density changes are estimated from the model R
l
DD
by assuming the amount of density change due to cabbeling. From these results, we conclude that Oyashio winter mixed-layer
water contributes to a freshening of the lighter layer of the NPIW salinity minimum (around 26.70σθ) in the MWR. |
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| Keywords: | North Pacific Intermediate Water Mixed Water Region mixing cabbeling double diffusion double-diffusive intrusion |
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