Temporal variation of the estimated volume transport through the Korea and Tsugaru Straits

1. PICES 14th Annual Meeting Sep. 29-Oct. 9, 2005, Vladivostok, Russia Temporal variation of the estimated volume transport through the Korea and Tsugaru Straits Hanna Na and Kuh Kim SEES, Seoul National University, E-mail: hanna@ocean.snu.ac.kr 4. VT through the Tsugaru Strait 1. Introduction Lack of continuous observation on transport through the straits Korea Strait Lyu & Kim, 2003: monitoring since 1998 using submarine cable Takikawa & Yoon, 2005: monitoring since 1997 using vessel mounted ADCP Tsugaru Strait Ito et al., 2003: Oct., 1999 ~ Mar., 2000 using vessel mounted ADCP Outflow Soya Strait Outflow Tsugaru Strait East Sea Fig.11. Regression Analysis between SLD (Tappi-Yoshioka) and VT (Ito et al., 2003). Solid line is the estimated VT and dotted line is the observed VT. • Study Objectives • Estimation of the VT through the Korea and Tsugaru Straits • for longer than decadal time scale • 2. Comparison of the temporal variation of the VT through the Korea and Tsugaru Straits • 3. Understanding of the inflow and outflow system of the East Sea Inflow Korea Strait Fig.1. Major Straits in the East Sea. Fig.12. Monthly means of the VT for 21 years and their variance conserved spectra. Fig.13. Mean seasonal variation of the VT. 2. Data and Methods Tide gauge Sea level data from the KODC and JODC Inverse Barometric Correction Using ECMWF Reanalysis sea level pressure Fig.15. Interannual variation of the VT. 13 month moving average of [Monthly means-mean seasonal variation]. Fig.14. Annual means of the VT. Fig.2. Sea level stations near the Korea Strait. Fig.3. Sea level stations near the Tsugaru Strait. Sea Level Difference (SLD) and Volume Transport (VT) The VT through the strait is linearly related to the cross-strait SLD according to the geostrophic balance. The correlation between temporal variation of the SLD and the VT has been studied through several researches. Through the regression analysis the conversion factor from the SLD to the VT can be calculated. By applying the conversion factor to the SLD, the VT is obtained for the longer period the sea level data have been measured. 5. Inflow and Outflow system of the East Sea 3. VT through the Korea Strait Fig.16. The ratio of the VT through the Tsugaru Strait to the Korea Strait. Light solid line shows the monthly mean and cross symbols indicate the annual mean. Right side of the bottom panel indicates the climatology of the ratio for 20 years. Fig.17. The difference of the VT between the Tsugaru Strait and the Korea Strait. Light solid line shows the monthly mean and cross symbols indicate the annual mean. Right side of the bottom panel indicates the climatology of the ratio for 20 years. Fig.5. Baroclinic part of the SLD calculated from KODC hydrography data. Fig.4. Station map of the Korea Strait and estimation of the baroclinic part of SLD (Lyu and Kim, 2003). • The ratio of the VT through the Tsugaru Strait to the Korea Strait • shows maximum on December. • The difference of the VT between the Tsugaru Strait and the Korea Strait shows minimum on December. • VT through the Korea and Tsugaru Straits show higher correlation and lower phase difference according to the period increase. • Coherency between VT through the two straits has the peak on the period of about 200days and 1 year. Fig.6. Regression analysis between corrected SLD and VT. Triangle: observed VT using submarine cable, circle: estimated VT from corrected SLD. Fig.7. Monthly means of the VT for 43 years and their variance conserved spectra. Fig.18. Coherency between VT through the Korea and Tsugaru Straits. Dot represents the phase difference between them. 6. Discussion Fig.8. Mean seasonal variation of the VT. Fig.19. Tide gauge station can be used to estimate the VT through the East of Taiwan, Taiwan Strait, Tokara Strait, Korea Strait, and Tsugaru Strait Fig.20. Monthly means of (top to bottom) VT through the Korea Strait, VT through the Tsugaru Strait, SLD across the Tokara Strait, SLD across the Taiwan Strait, and SLD of the east of Taiwan. Fig.9. Annual means of the VT. The index of the VT variation through the East of Taiwan, Taiwan Strait, Tokara Strait also can be estimated. The correlation between them and the VT through the straits in the East Sea can be understood on the long-term time scale. References [1] Ito, T., O. Togawa, M. Ohnishi, Y. Isoda, T. Nakayama, S. Shima, H. Kuroda, M. Iwahashi, and C. Sato, Variation of velocity and volume transport of the Tsugaru Warm Current in the winter of 1999-2000, Geophysical Research Letters, 30(13), 1678, 2003. [2] Lyu, S. J., and K. Kim, Absolute transport from the sea level difference across the Korea Strait, Geophysical Research Letters, 30(6), 1285, 2003. [3] Takikawa, Tetsutaro, and J. H. Yoon, Volume transport through the Tsushima Straits estimated from sea level difference, Journal of Oceanography, Vol. 61 (No. 4), pp. 699-708, 2005 Fig.10. Interannual variation of the VT. 13 month moving average of [Monthly means-mean seasonal variation].