Water mass exchange and diapycnal mixing at Bussol’ Strait revealed by water mass properties |
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| Authors: | Kazuya Ono Kay I Ohshima Tokihiro Kono Motoyo Itoh Katsuro Katsumata Yuri N Volkov Masaaki Wakatsuchi |
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| Institution: | (1) Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan;(2) Department of Marine Science and Technology, Hokkaido Tokai University, Sapporo 005-8601, Japan;(3) Japan Marine Science and Technology Center, Yokosuka 237-0061, Japan;(4) Far Eastern Regional Hydrometeorological Research Institute, Vladivostok, Russia |
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| Abstract: | Intensive CTD observations that resolve the mean and tidal components were done with a total of 129 casts in summer of 2001
at Bussol’ Strait. Based on these data and all the available historical data, we have revealed the outflow from Bussol’ Strait
to the Pacific and the significant diapycnal mixing in the strait. In the range 27.0−27.3σ
θ
, the water property in Bussol’ Strait is almost identical to that of the Kuril Basin Water (KBW). The KBW out of Bussol’
Strait forms a water mass front with the East Kamchatka Current Water (EKCW). This front also corresponds to the front of
the Oyashio Current. In the lower part of the intermediate layer (27.3−27.6σ
θ
), part of the water in the strait is characterized by lower temperature, lower salinity, and higher dissolved oxygen than
that of KBW and EKCW, which can be explained only by the diapycnal mixing. The strong diapycnal mixing in the strait can also
be shown by the density inversion, occurrence frequency of which corresponds well to the amplitude distribution of the diurnal
current. In the density range 26.7−26.8σ
θ
, the water in Bussol’ Strait has the lowest potential vorticity, suggesting that it is a source region of the low potential
vorticity water. Seasonal change of the water can reach up to a density of 26.8σ
θ
around Bussol’ Strait. This leads us to propose that the combination of winter convection and local tidal mixing leads to
effective ventilation of the intermediate layer. |
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| Keywords: | Bussol’ Strait Sea of Okhotsk intermediate water water mass analysis water exchange diapycnal mixing tidal mixing |
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