Variation of velocity and volume transport of the Tsugaru Warm Current in the winter of 1999–2000

Abstract

The variation of velocity and volume transport of the Tsugaru Warm Current (TWC) is investigated based on the data of continuous and cross‐sectional current monitoring in the Tsugaru Strait. During November 1999–March 2000, the structure of the velocity transection across the strait was almost stable in which the TWC occupied the central part of the strait, while the returning flows existed in the northern and southern part of the strait, and the velocity of these flows decreases with time. The volume transport of the TWC varies from 2.1 to 1.1 Sv, with the mean value of 1.5 Sv, following the variation of the TWC. The temporal variation of the volume transport shows a linear correlation with that of the sea level difference between the Japan Sea and the Pacific Ocean. The contribution of the sea level difference to the volume transport is estimated to be roughly 70%.

High-resolution numerical simulation of the Pacific Ocean

“…Figure 17 presents schematic views of annual mean volume transports calculated by the 1/6° and 1/12° models through the major channels of the northwestern Pacific Ocean. The annual mean modeled volume transports agree very well with previous well-known observation results (Fang et al, 1991;Ichikawa and Beardsley, 1993;Chu et al, 2000;Johns et al, 2001;Imawaki et al, 2001, Ito et al, 2003Nishida et al, 2003;Takikawa et al, 2005). The largest difference in volume transport between the two models is for Kuroshio volume transport south of Japan, which increased from 50.91 Sv in the 1/6° model to 58.95 Sv in the 1/12° model.…”

“…Despite many previous research efforts, understanding is still lacking regarding the variation of volume transport through the major channels of the northwestern Pacific Ocean. The main reason is that most observation studies have indirectly estimated volume transport based on geostrophic calculation using spatially and temporally discrete hydrographic data; exceptions include a few long-term direct monitoring studies such as Takikawa et al's (2005) study of the Tsushima/Korea Strait and Ito et al's (2003) examination of the Tsugaru Strait. The present result of high correlation of volume transport between the model and observation indicates that the model provides a practical way to investigate long-term variation of volume transport.…”

Wind-driven intensification of the Tsushima Warm Current along the Japanese coast detected by sea level difference in the summer monsoon of 2013

“…The sea level at Busan (1C) was provided by a database of the Institute for the Protection and Security of the Citizen (IPSC). The variations through the Tsushima Straits, its eastern channel (Takikawa and Yoon, 2005), the Tsugaru Strait (Ito et al, 2003), and the Soya Strait (Ebuchi et al, 2006) were estimated using the SLD between Hakata (1A) and Busan (1C), Hakata (1A) and Izuhara (1B), Fukaura (7A) and Hakodate (7B), and Wakkanai (8A) and Abashiri (8B), respectively. We used sea level data at coastal stations (3A: Sakai, 4A: Noto, 5A: Niigata-nishi, and 6A: Esashi) and at remote islands (3B: Saigo, 4B: Hegura, 5B: Sado, and 6B: Okushiri) to estimate the coastal variations of the first branch of the Tsushima Warm Current.…”

Four-dimensional variational ocean reanalysis: a 30-year high-resolution dataset in the western North Pacific (FORA-WNP30)

“…Because of the semienclosed character, volume transports through the straits are thought to be important for mean state and variability in the Japan Sea. This is why a number of observational studies have attempted to estimate an accurate volume transport through each strait (e.g., Fukudome et al 2010;Ito et al 2003;Fukamachi et al 2010). Recent observational efforts are well summarized in Na et al (2009).…”

“…(Fukudome et al 2010) (Ito et al 2003) (Fukamachi et al 2008(Fukamachi et al , 2010 Trend (Sv/year) 1.62 × 10 −2 6.12 × 10 −3 9.28 × 10 −3 8.62 × 10 −4 transport through TGR as 1.5 Sv using ADCP data from November 1999 to March 2000. Although this observation is conducted only in a short term, this value is almost the same as other observational results (Shikama 1994;Nishida et al 2003).…”