• Fisheries and Aquatic Sciences
• /
• v.1 no.1
• /
• pp.113-121
• /
• 1998

A relationship between sea level variations in the Korea Strait (the western and the eastern channels) and the Tokara Strait in the Kuroshio region is examined using daily-mean sea level data from 1966 to 1986. The seasonal variation of the sea level difference (SLD) between Izuhara and Pusan (the western channel) is most periodic: the positive anomalies appear from summer to autumn, and the negative anomalies from winter to spring year to year, whereas SLDs neither between Hakata and Izuhara (the eastern channel) nor between Naze and Nishinoomote (the Tokara Strait) show such a periodic variation. Much similarity has been found between SLDs in the eastern channel and the Tokara Strait, and in particular they were closely correlated in a special event of the Kuroshio region, such as a large meander of the Kuroshio. This paper shows that the periodic seasonal variation of the SLDs in the western channel should be less related to the Kuroshio region. This result also implies that the variation of SLD in the western channel is largely influenced by local factors, such as the bottom cold water in the western channel in summer, rather than from the Kuroshio region.

• Journal of the korean society of oceanography
• /
• v.37 no.3
• /
• pp.160-168
• /
• 2002

We have been measuring the voltage differences by using submarine cables in the Tsushima and in the Tokara Straits. The aim of these measurements is to estimate the volume transports of the ocean currents through those straits. In this paper, the voltage differences are compared with the corresponding sea level and air pressure differences between straits. Especially in the Tsushima Strait, the voltage difference is consistent with the air pressure difference as well as the sea level difference.

• Journal of the korean society of oceanography
• /
• v.32 no.1
• /
• pp.1-7
• /
• 1997

Surface current fields in the eastern East China Sea (ECS) were constructed by analyzing trajectories of 58 satellite-tracked surface drifters released during 1991-1996. Composite trajectories and 20-minute-by-20-minute box-averaged current vectors show that the basic current pattern composes of: the Kuroshio main stream, which turns eastward toward the Tokara Strait; a northward branch current of the Kuroshio on the ECS outer shelf deeper than 100 m; and an anticyclonic circulation in the northern Okinawa Trough west of Kyushu. The northward branch current sharply changes its direction to the northeast when it crosses a line connecting Cheju Island, Korea and Goto Islands, Japan. The basic pattern of current field changes slightly from winter to summer, and the main axis of the Tsushima Current in the Korea Strait is found to shift seasonally. The drifter experiment does not support the claim that the Yellow Sea Warm Current is separated from the northward branch current on the outer shelf southeast of Cheju Island. We suggest that the use of the term 'Tsushima Current' be limited to the northeast channel flow in the Korea Strait. The new term 'Kuroshio Branch Current' is suggested for the northward branch current on the outer shelf south of Cheju-do, which is separated from the Kuroshio.

• Journal of the korean society of oceanography
• /
• v.37 no.3
• /
• pp.196-200
• /
• 2002

The time variation in the Kuroshio is studied by use of nine observed distances of the main Kuroshio axis from the Japanese coast. The observed distances over 1975 - 1995 are estimated from the Prompt Report of Oceanographic Conditions published by Hydrographic Department of the Maritime Safety Agency of Japan. It is shown that large sea level difference between Naze and Nishinoomote, which represents the volume transport of the southern inflow south of Kyushu, coincides with larger distance of the Kuroshio in the upstream area from off Kyushu to off eastern Kii Peninsula and smaller distance in the downstream area from off Omae-zaki to off Boso Peninsula. In contrast, large sea level difference between Nishinoomote and Aburatsu, which represents the volume transport of northern inflow south of Kyushu, corresponds to smaller distance in the upstream area and larger distance in the downstream area. Path dynamics of the Kuroshio is discussed with reference to the variation in Volume transport south of Kyushu.

• Molecules and Cells
• /
• v.21 no.1
• /
• pp.89-103
• /
• 2006

Population structure was investigated in Reticulitermes speratus populations in the Korean Peninsula and the Japanese Archipelago. All trees derived from analyses of the combined sequence dataset of two mitochondrial genes, COII and COIII, showed that R. speratus populations cluster into two major clades comprising the Korean/southern Japanese populations and the northern Japanese populations. Analysis of population genetic structure showed strong genetic partitioning between populations of the two clades. To understand historical migration routes and current distributions, the phylogeographic history of R. speratus was inferred from intra-/interspecific phylogeny and divergence times estimated between the clades of the phylogenetic tree. The estimated migration route and divergence time of ancestral R. speratus are congruent with recent paleogeographic hypotheses involving land-bridge connections between the Asian continent and the Japanese Archipelago. We suggest that ancestral R. speratus separated into northern and southern Japanese populations after its migration into the Japanese main islands from East China during the early Pleistocene via the East China Sea basin, which may have been exposed during that period. The Korean populations seem to have diverged recently from southern Japanese populations; this may explain the current distribution of R. speratus in the Japanese Arachipelago, and account for why it is restricted to northern areas of the Tokara Strait.