TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 62 (No. 1), pp. 105-113, 2006

Prediction of Slope Water Intrusion into the Kii Channel in Summer

Toshinori Takashi1,2*, Tateki Fujiwara1, Toshiaki Sumitomo3 and Wataru Sakamoto2

1Laboratory of Fisheries and Environmental Oceanography, Graduate School of Agriculture, Kyoto University, Kyoto 606-8561, Japan
2Fisheries Laboratory of Kinki University, Wakayama 649-2211, Japan
3Fisheries Division, Tokushima Prefectural Government, Tokushima 770-8570, Japan

(Received 8 March 2005; in revised form 22 October 2005; accepted 22 October 2005)

Abstract: Intrusions of the warm, oligotrophic surface slope water (SSW) and the cold, nutrient-rich bottom slope water (BSW) from the continental slope influence the annual variations in water temperature and nutrient concentrations in the Kii Channel in August. In order to evaluate the relationships between both these intrusions and the distance of the Kuroshio axis from Cape Shionomisaki (Kuroshio distance), a Distance-Intrusion-Diagram (DID) for temperature, which can reproduce the vertical temperature profile of the channel, was constructed by analyzing the temperature and Kuroshio distance records in August for 1967-2001. DIDs for nutrients (nitrate and phosphate) are also constructed by using the relationship between the nutrient concentration and water temperature. The only explanatory variable in the DIDs is the Kuroshio distance. The DID for temperature predicts that the SSW occupies almost the entire water column when the Kuroshio approaches Cape Shionomisaki (Kuroshio distance = 18.5 km). When the Kuroshio distance lies in the range 18.5-74 km, the BSW thickness increases proportionally to the Kuroshio distance increment while the SSW thickness decreases. The BSW occupies the largest portion of the channel when the Kuroshio distance is 74 km. Further, beyond 74 km, the BSW thickness reduces gradually. Yearly variations in the temperature and concentrations of nitrate and phosphate were hindcast with the DIDs. The results revealed that the Kuroshio distance contributes 70%, 35%, and 30% of the variances in temperature, nitrate concentration, and phosphate concentration, respectively.

*Corresponding author E-mail: takashi@coral.cypress.ne.jp

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