Examining a Transport Pathway in the East Sea/Sea of Japan
Abstract
The East/Japan Sea (JES) is a marginal sea surrounded by Korea, Russia, and Japan. The Tsushima Warm Current (TWC) is one of the major flows into the JES, entering through the Korea/Tsushima Strait. The TWC is known to split into three main branches in the southern part of the JES: the first and second branches that split South (nearshore branch) and North of Tsushima Island (offshore branch), respectively, and the East Korea Warm Current (EKWC), which hugs the Korean coast as it flows northward. Results from a December 2021 drifter release reveal a surface current flowing eastward along the southern margin of the Ulleung Basin in the southwestern JES, which suggests a more northern pathway connecting the EKWC with the nearshore branch of the TWC along the coast of Japan. Contemporary drifter trajectories within high-resolution ocean models reveal a consistent pattern. Dispersion estimates from the drifter release reveal nonlocal processes influence spreading at scales below 10km, and local processes dominate at larger scales, which is consistent with the regional internal Rossby radius. We present estimates of TWC branch transports using 24 years of geostrophic velocity derived from satellite altimetry. This analysis suggests that the along-shelf transport is significant to the regional flow. Time-averaged along-shelf transport accounts for approximately 16 percent of the total TWC transport of 2.6 Sverdrups (Sv), with a seasonal maximum of between 0.5 and 1 Sv occurring in July-August. The along-shelf transport also exhibits a greater degree of 30-60 day sub-seasonal variability than is observed in other TWC branches (offshore branch and EKWC). This variability is also confirmed in an 8-month long nearby moored velocity record. Relative vorticity derived from satellite altimetry shows little difference between upstream conditions during high and low transport.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 20, 2024
- Accession Number
- AD1229196
Entities
People
- Conrad A. Luecke
Organizations
- United States Naval Research Laboratory