Title: Temporal variation of the estimated volume transport
1PICES 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_at_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.