Vertical structure of low-frequency currents in the southwestern East Sea (Sea of Japan)

The vertical structure of low-frequency flows in the central Ulleung Interplain Gap of the southwestern East Sea (Sea of Japan) is analyzed based on full-depth current measurement during November 2002–April 2004. Record-length mean flows are directed toward the Ulleung Basin (Tsushima Basin) throughout the entire water column. Upper current variability above the permanent thermocline with a dominant period of about 50–60 days is shown to be closely related to the displacement of an anticyclonic warm eddy associated with the westward meander of the Offshore Branch. Fluctuations of deep currents below the permanent thermocline have a dominant period of about 40 days. Coherence between the current near the seabed and shallower depths is statistically significant up to 360 m for a period range between 15 and 100 days, but less significantly correlated with currents in the upper 200 m. Data from the densely equipped mooring line reveal that mean and eddy kinetic energies are minima at 1000 m, where isotherm slopes are also relatively flat. Empirical orthogonal function (EOF) analyses suggest that more than 79% of total variances of upper and deep currents can be explained by their respective first EOF mode characterized by nearly depth-independent eigenvectors. Spectral and EOF analyses of observed currents suggest that most of the deep current variability is not directly related to local upper current variability during the observation period.     

210Pb-derived sediment accumulation rates in the southwestern East Sea (Sea of Japan)

 Recent sediment accumulation rates are 18–230 mg cm^-2 yr^-1 (0.02–0.2 cm yr^-1) based on excess ²¹⁰Pb activity profiles in the southwestern part of the East Sea (Sea of Japan). Assuming no mixing beneath surface mixed layers, ²¹⁰Pb-derived sediment accumulation rates are 18–32 mg cm^-2 yr^-1 in the northern part of the Yamato Ridge and the Ulleung Basin, 29–136 mg cm^-2 yr^-1 in the Korea Plateau, and 230 mg cm^-2 yr^-1 in the southern shelf. These values generally agree with long-term sedimentation rates estimated from dated ash layers. Received: 6 October 1995 / Revision received: 31 May 1996     

Eddies in the southwestern East/Japan Sea

Closed loop mesoscale eddies were identified and tracked in the Ulleung Basin of the southwestern Japan/East Sea (JES) using the winding-angle (WA) methodology, for mapping the absolute geostrophic currents into surface streamlines of flow. The geostrophic velocity used here was the sum of the Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO), time variable velocity and the 1992–2007 mean geostrophic velocity. Local sampling bias was removed using the drifter observations. This WA methodology of deriving the Lagrangian path lines that drifters followed over a 7-day period was validated by individual drifter tracks and it demonstrated closed looping eddy motions. The WA method demonstrated that less than 6% of the closed streamlines appeared when drifters did not show a closed loop in their vicinity, compared to 30% of the excess detection rate by the Okubo–Weiss method of locating closed loop structures. Three groups of eddies were identified: (1) Coastal Cold and Warm Eddies, which appeared in the area between the coast of southern Korea and the East Korean Warm Current (EKWC), when a southward coastal current was present, (2) Frontal Cold and Warm Eddies, which were formed in the region of the seaward extension of the meandering EKWC, north of Ulleung Island and (3) Ulleung Warm Eddies (UWE) and Dok Cold Eddies (DCE), which appeared during meanders of the EKWC, in the Ulleung Basin. No seasonal concentration for eddy generation and eddy population was found. The average radius of eddies was about 38–60 km. These were born, moved in an erratic pattern and then died in the vicinity where the EKWC separated from the coast and formed a large meander. The time-mean large meander formed meridionally concentrated bands of positive and negative relative vorticity. The cyclonic (cold) eddies tend to reside within the band of positive time-mean relative vorticity, and the anticyclonic (warm) eddies reside within the bands of negative relative vorticity. Six UWE and four warm eddies, in the Yamato Basin (about 10% of warm eddies), were sustained longer than a year. Because the large meander of the EKWC appeared to be controlled by topography, and the JES is a nearly enclosed basin with rapid flow-out to the east through the narrow Tsugaru Strait, there was little eddy energy propagation to the west. The warm eddies in the southwestern part of the JES appeared to be interacting very locally with the mean flow.     

Sulfate reduction and sulfide deposition in deep-sea sediments from the southwestern Japan Sea

Vertical profiles of total sulfur and organic carbon have been measured in two deep-sea piston cores from the southwestern Japan Sea where sulfate reduction is proceeding within the sediments. The content of total sulfur, most of which is present as pyrite, increases gradually with increasing depth, showing several peaks. The amount of diagenetically deposited sulfide-sulfur is estimated using a steady-state model that considers vertical change in the diffusion coefficient. It is suggested that two-thirds to three-fourths of the observed total sulfur content has been deposited diagenetically.     

Distribution of 210Po and export of organic carbon from the euphotic zone in the southwestern East Sea (Sea of Japan)

The distribution of the natural radionuclide ²¹⁰Po in the water column along a horizontal transect of the continental shelf, slope and deep basin regions of the East Sea (Sea of Japan), a marginal sea of the Northwest Pacific Ocean, was investigated, and its behavior is described here. The settling fluxes of particulate ²¹⁰Po in the deep basin along with ²¹⁰Pb, ²³⁴Th and biogenic matter were also determined. ²¹⁰Po inventories in the water column were observed to decrease from winter to summer in all stations, probably due to increased influx of ²¹⁰Po-poor Kuroshio Water of the Northwest Pacific Ocean during summer. Vertical profiles of dissolved and particulate ²¹⁰Po along with the settling fluxes of particulate ²¹⁰Po in the deep basin station have enabled us to evaluate temporal variations and residence times of ²¹⁰Po. In the slope and basin, activities of dissolved ²¹⁰Po generally decreased from the surface to the bottom water, with maximum activity just below the subsurface chlorophyll a maximum at 50–75 m depth in spring and summer. These subsurface peaks of dissolved ²¹⁰Po activity were attributed to the release of ²¹⁰Po from the decomposition of ²¹⁰Po-laden biogenic particulate organic matter. In the deep basin, despite the decrease in total mass flux, the sinking flux of particulate ²¹⁰Po was higher in the deeper trap (2000 m) than in the shallower one (1000 m), probably due to scavenging of dissolved ²¹⁰Po from the water column during particle descent and/or break-down of ²¹⁰Po-depleted particulate matter between 1,000 m and 2,000 m depths. In general, the ratios of the particulate phase to the dissolved phase of ²¹⁰Po (K_d) increased with depth in the slope and basin stations. ²¹⁰Po removal from the water column appears to depend on the primary productivity in the upper waters. There is an inverse relationship between K_d and suspended particulate matter (SPM) concentration in the water column. From the ²¹⁰Po activity/chlorophyll a concentration ratios, it appears that sinking particles arriving at 1000 m depth were similar to those in the surface waters.     

Distribution and origin of shallow gas in deep-sea sediments of the Ulleung Basin, East Sea (Sea of Japan)

A synthesis of high-resolution (Chirp, 2–7 kHz) subbottom profiles in the Ulleung Basin reveals patchy distribution of shallow (<90 m subbottom depth) gassy sediments in the eastern basin plain below 1,800-m water depth. The shallow gases in the sediments are associated with acoustic turbidities, columnar acoustic blankings, enhanced reflectors, dome structures, and pockmarks. Analyses of gas samples collected from a piston core in an earlier study suggest that the shallow gases are thermogenic in origin. Also, published data showing high amounts of organic matter in thick sections of marine shale (middle Miocene to lower Pliocene sequence) and high heat flow in the basin plain sediments are consistent with the formation of deep, thermogenic gas. In multi-channel deep seismic profiles, numerous acoustic chimneys and faults reflect that the deep, thermogenic gas would have migrated upwards from the deeper subsurface to the near-seafloor. The upward-migrating gases may have accumulated in porous debrites and turbidites (upper Pliocene sequence) overlain by impermeable hemipelagites (Quaternary sequence), resulting in the patchy distribution of shallow gases on the eastern basin plain.     

Circulation and currents in the southwestern East/Japan Sea: Overview and review

A review is made of circulation and currents in the southwestern East/Japan Sea (the Ulleung Basin), and the Korea/Tsushima Strait which is a unique conduit for surface inflow into the Ulleung Basin. The review particularly concentrates on describing some preliminary results from recent extensive measurements made after 1996. Mean flow patterns are different in the upstream and downstream regions of the Korea/Tsushima Strait. A high velocity core occurs in the mid-section in the upstream region, and splits into two cores hugging the coasts of Korea and Japan, the downstream region, after passing around Tsushima Island located in the middle of the strait. Four-year mean transport into the East/Japan Sea through the Korea/Tsushima Strait based on submarine cable data calibrated by direct observations is 2.4 Sv (1 Sv = 10⁶ m³ s⁻¹). A wide range of variability occurs for the subtidal transport variation from subinertial (2–10 days) to interannual scales. While the subinertial variability is shown to arise from the atmospheric pressure disturbances, the longer period variation has been poorly understood.Mean upper circulation of the Ulleung Basin is characterized by the northward flowing East Korean Warm Current along the east coast of Korea and its meander eastward after the separation from the coast, the Offshore Branch along the coast of Japan, and the anticyclonic Ulleung Warm Eddy that forms from a meander of the East Korean Warm Current. Continuous acoustic travel-time measurements between June 1999 and June 2001 suggest five quasi-stable upper circulation patterns that persist for about 3–5 months with transitions between successive patterns occurring in a few months or days. Disappearance of the East Korean Warm Current is triggered by merging the Dok Cold Eddy, originating from the pinching-off of the meander trough, with the coastal cold water carried Southward by the North Korean Cold Current. The Ulleung Warm Eddy persisted for about 20 months in the middle of the Ulleung Basin with changes in its position and spatial scale associated with strengthening and weakening of the transport through the Korea/Tsushima Strait. The variability of upper circulation is partly related to the transport variation through the Korea/Tsushima Strait. Movements of the coastal cold water and the instability of the polar front also appear to be important factors affecting the variability.Deep circulation in the Ulleung Basin is primarily cyclonic and commonly consists of one or more cyclonic cells, and an anticyclonic cell centered near Ulleung Island. The cyclonic circulation is conjectured to be driven by a net inflow through the Ulleung Interplain Gap, which serves as a conduit for the exchange of deep waters between the Japan Basin in the northern East Sea and the Ulleung Basin. Deep currents are characterized by a short correlation scale and the predominance of mesoscale variability with periods of 20–40 days. Seasonality of deep currents is indistinct, and the coupling of upper and deep circulation has not been clarified yet.     

Water masses and decadal variability in the East Sea (Sea of Japan)

Water masses in the East Sea are newly defined based upon vertical structure and analysis of CTD data collected in 1993–1999 during Circulation Research of the East Asian Marginal Seas (CREAMS). A distinct salinity minimum layer was found at 1500 m for the first time in the East Sea, which divides the East Sea Central Water (ESCW) above the minimum layer and the East Sea Deep Water (ESDW) below the minimum layer. ESCW is characterized by a tight temperature–salinity relationship in the temperature range of 0.6–0.12 °C, occupying 400–1500 m. It is also high in dissolved oxygen, which has been increasing since 1969, unlike the decrease in the ESDW and East Sea Bottom Water (ESBW). In the eastern Japan Basin a new water with high salinity in the temperature range of 1–5 °C was found in the upper layer and named the High Salinity Intermediate Water (HSIW). The origin of the East Sea Intermediate Water (ESIW), whose characteristics were found near the Korea Strait in the southwestern part of the East Sea in 1981 [Kim, K., & Chung, J. Y. (1984) On the salinity-minimum and dissolved oxygen-maximum layer in the East Sea (Sea of Japan), In T. Ichiye (Ed.), Ocean Hydrodynamics of the Japan and East China Seas (pp. 55–65). Amsterdam: Elsevier Science Publishers], is traced by its low salinity and high dissolved oxygen in the western Japan Basin. CTD data collected in winters of 1995–1999 confirmed that the HSIW and ESIW are formed locally in the Eastern and Western Japan Basin. CREAMS CTD data reveal that overall structure and characteristics of water masses in the East Sea are as complicated as those of the open oceans, where minute variations of salinity in deep waters are carefully magnified to the limit of CTD resolution. Since the 1960s water mass characteristics in the East Sea have changed, as bottom water formation has stopped or slowed down and production of the ESCW has increased recently.     

Recent sediments of the southwestern Barents Sea

The paper is based on textural, mineralogical and chemical studies of surface and subsurface sediments from 80 stations in the southwestern Barents Sea. Dispersed phases are quantitatively insignificant in these oxic shelf sediments and it is argued that the deposits are predominantly terrigenous in origin. A combined analysis of the mineralogy and chemistry of the separated size fractions allows the recognition of petrographic provinces. The patterns of sediment dispersal are discussed. The coarsest components of the Barents Sea sediments are of local origin whereas long-distance transport of finer material is taking place.     

The Air-Sea Exchange of CO2 in the East Sea (Japan Sea)

During CREAMS expeditions, fCO₂ for surface waters was measured continuously along the cruise tracks. The fCO₂ in surface waters in summer varied in the range 320–440 μatm, showing moderate supersaturation with respect to atmospheric CO₂. In winter, however, fCO₂ showed under-saturation of CO₂ in most of the area, while varying in a much wider range from 180 to 520 μatm. Some very high fCO₂ values observed in the northern East Sea (Japan Sea) appeared to be associated with the intensive convection system developed in the area. A gas-exchange model was developed for describing the annual variation of fCO₂ and for estimating the annual flux of CO₂ at the air-sea interface. The model incorporated annual variations in SST, the thickness of the mixed layer, gas exchange associated with wind velocity, biological activity and atmospheric concentration of CO₂. The model shows that the East Sea releases CO₂ into the atmosphere from June to September, and absorbs CO₂ during the rest of the year, from October through May. The net annual CO₂ flux at the air-sea interface was estimated to be 0.032 (±0.012) Gt-C per year from the atmosphere into the East Sea. Water column chemistry shows penetration of CO₂ into the whole water column, supporting a short turnover time for deep waters in the East Sea. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fluctuations of the calcite compensation depth (CCD) in the East Sea (Sea of Japan)

Variations in the calcite compensation depth (CCD) in the East Sea (Sea of Japan) since the early middle Miocene were inferred from data on age-depth relationships, sediment carbonate, and benthic foraminifers from ODP sites 794, 795, and 797. The CCD remained relatively shallow during much of the middle Miocene–Pliocene, and deepened sharply at the beginning of the Pleistocene. Since then it has fluctuated rapidly, possibly in relation to the onset of the northern hemisphere glacial cycles in the late Pliocene. The average CCD has deepened since at least the early middle Miocene, coinciding with the long-term drop in eustatic sea level. Received: 5 November 1998 / Revision accepted: 2 February 2000     

Sinking fluxes of particulate U-Th radionuclides in the East Sea (Sea of Japan)

A record of radionuclide fluxes at a deep marginal sea of the Northwest Pacific Ocean (39°40′N 132°24′ E, Japan Basin, East Sea/Sea of Japan) was obtained from analysis of a 1-year continuous collection of sediment-trap samples. The trap was placed at a depth of 2800 m, 500 m above the sea floor, and the samples were recovered at the end of one year. Concentrations of ²³⁸U, ²³⁴U, ²³²Th, ²³⁰Th and ²²⁸Th were measured in the trapped material. All of the radionuclide fluxes showed seasonal variations that were in phase with the variations in total particle flux, which were shown in earlier work to be closely tied to the primary production in the surface water. The formation of authigenic ²³⁸U appears to be less than in other open ocean regimes. The residence time of particulate thorium isotopes were of the order of a year, resulting in an average settling rate of a meter per day. Comparison of the measured ²³⁰Th_ex flux with that of the theoretical production in the overlying water column yielded about 40% surplus of ²³⁰Th, indicating that lateral advection contributes ²³⁰Th to this sampling site.     

Phosphorus regeneration and burial in near-shore marine sediments (the Gulf of Trieste, northern Adriatic Sea)

According to bioassay studies and high dissolved nutrient N/P ratios in the seawater column, phosphorus (P) is thought to control marine productivity in the northern Adriatic Sea. P in near-shore marine sediments of the Gulf of Trieste, the northernmost part of the Adriatic Sea, was investigated using pore water P distributions, and benthic P flux studies under oxic and anoxic conditions. The data show that P regeneration is up to three-fold more extensive in sediments overlain by oxygen-depleted waters and proceeds in parallel with Fe and Mn enhanced benthic fluxes. It appears from the incubation experiments that degradation of sedimentary organic matter is the main contribution to the flux of P at the sediment–water interface, while the release of phosphate adsorbed on the iron oxide surface is of minor importance.It appears that about 50% of P in the Gulf of Trieste is retained within in the sediments, probably bonded to clay minerals and carbonate grains or precipitated as fluoroapatite. In these sediments total P (P_tot) is preserved preferentially over organic C (C_org). P regenerated from surficial sediments contributes about 1/3 of the P that is assimilated by benthic microalgae. The phytoplankton P requirement should be entirely supplied from fresh-water sources. These results suggest that oxygen depletion in coastal areas caused by eutrophication enhances P regeneration from sediments, providing the additional P necessary for increased biological productivity. The development of anoxic bottom waters in coastal areas enhances the recycling of P, exacerbating the nutrient requirement in the area. A geochemical record of P burial in a longer sedimentary sequence revealed an increasing trend of P_tot and organic P (P_org) contents occurring approximately 50 years BP (after 1950), probably due to increasing use of inorganic fertilizers and detergents in the area.     

Mean flow and variability in the southwestern East Sea

The Ulleung Basin is one of three deep basins that are contained within the East/Japan Sea. Current meter moorings have been maintained in this basin beginning in 1996. The data from these moorings are used to investigate the mean circulation pattern, variability of deep flows, and volume transports of major water masses in the Ulleung Basin with supporting hydrographic data and help from a high-resolution numerical model. The bottom water within the Ulleung Basin, which must enter through a constricted passage from the north, is found to circulate cyclonically—a pattern that seems prevalent throughout the East Sea. A strong current of about 6 cms⁻¹ on average flows southward over the continental slope off the Korean coast underlying the northward East Korean Warm Current as part of the mean abyssal cyclonic circulation. Volume transports of the northward East Korean Warm Current, and southward flowing East Sea Intermediate Water and East Sea Proper Water are estimated to be 1.4 Sv (1 Sv=10⁻⁶ m³ s⁻¹), 0.8 Sv, and 3.0–4.0 Sv, respectively. Deep flow variability involves a wide range of time scales with no apparent seasonal variations, whereas the deep currents in the northern East Sea are known to be strongly seasonal.     

Supply of Heat by Tsushima Warm Current in the East Sea (Japan Sea)

A significant surface net heat loss appears around the Kuroshio and the Tsushima Warm Current regions. The area where the surface heat loss occurs should require heat to be supplied by the current to maintain the long-term annual heat balance. Oceanic heat advection in these regions plays an important role in the heat budget. The spatial distribution of the heat supply by the Tsushima Warm Current near the surface was examined by calculating the horizontal heat supply in the surface layer of the East Sea (the Japan Sea) (ESJS), directly from historical sea surface temperature and current data. We have also found a simple estimation of the effective vertical scale of heat supply by the current to compensate net heat loss using the heat supplied by the current in the surface 10 m layer. The heat supplied by the current for the annual heat balance was large in the Korea/Tsushima Strait and along the Japanese Coast, and was small in the northwestern part of the ESJS. The amount of heat supplied by the current was large in the northwestern part and small in the south-eastern part of the ESJS. These features suggest that the heat supplied by the Tsushima Warm Current is restricted to near the surface around the northeastern part and extends to a deeper layer around the southeastern part of the ESJS. This revised version was published online in August 2006 with corrections to the Cover Date.     

Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan)

The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s (SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm³ between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.     

Phosphorus regeneration vs. burial in sediments of the Arabian Sea

Solid-phase phosphorus (P) speciation and benthic phosphate fluxes have been determined in Arabian Sea sediments. Benthic phosphate fluxes are highest in the continental slope sediments, underlying bottom waters with low oxygen concentrations. Organic matter degradation and phosphate desorption from iron oxides do not produce sufficient phosphate to explain these high phosphate fluxes. The potentially high deposition of P associated with fish debris (P_fish) in the Arabian Sea, and a good correlation between benthic phosphate fluxes and P_fish accumulation rates suggest that benthic phosphate fluxes in these sediments are to a large extent governed by dissolution of biogenic apatite. Factors controlling dissolution and preservation of fish debris, therefore, may play an important role in the burial and regeneration of P in continental margin sediments. A sharp decrease of the reactive P accumulation rate with increasing water depth, in combination with rather constant primary productivity rates throughout the northern Arabian Sea, indicates that P burial in continental margin sediments located within the OMZ is more efficient than in deep basin sediments. The effectiveness of P burial is to a large extent regulated by P regeneration occurring in the water column and redeposition processes. Sedimentary phosphorus burial efficiencies, thus, should be interpreted with caution in terms of the environmental conditions.     

Composition and properties of glacigenic sediments in the southwestern Barents Sea

Abstract

The composition and properties of glacigenic sediments in the southwestern Barents Sea are described based on data from 33 shallow boreholes (< 143 m below seabed) and 11 seabed cores (<4.2m below seabed). The cores are tied into a regional seismostratigraphic framework, illustrating the relationships between different boreholes.

A massive, muddy diamicton (silty, sandy clay with scattered gravel) is found in nearly all cores. Average clay content (<2 pm) of this lithology is about 38%, but varies between about 25% and 50%. Short intervals of finely laminated, waterlain sediments or gravelly sand are cored in a few occasions. A high content of sand and gravel in the cores from near the Norwegian coast shows an influence of sediment input from the mainland, while material eroded from sedimentary rocks dominates farther offshore.

The data presented on physical properties include undisturbed and remolded undrained shear strength, natural water content, bulk density, compressional sound velocity (P waves), Atterberg consistency limits, effective preconsolidation pressure, and consolidation coefficient.

Prediction of overconsolidation from seismic mapping of erosional surfaces is confirmed by the borehole cores. High compaction is found both in Weichselian and older deposits, with a general increase in compaction toward the east as well as toward shallower water. Cores that are “underconsolidated” at their present burial depth are also reported.

The average compressional sound velocity is about 1780 m/s for the borehole cores, 1550 m/s for the seabed cores, and increases with increasing shear strength and consolidation. Both horizontal and vertical sound velocities are measured in several cores, and although the data have a considerable scatter, a slightly aniso‐tropic sound velocity is indicated.     

Surface circulation in the southwestern Japan/East Sea as observed from drifters and sea surface height

The mean circulation of the surface layer of the southwestern Japan/East Sea (JES) was examined using current measurements collected at 15 m by satellite-tracked drifters and merged sea level anomalies from satellite altimeters. The study of circulation patterns in this paper focused on the inflow passing through the western channel of the Korea Strait from the East China Sea. Empirical Orthogonal Function (EOF) analysis of non-seasonal sea level anomalies revealed that significant energy in the circulation pattern of Ulleung Basin was controlled by the inflow conditions through the Korea Strait. Three circulation patterns were identified that depended on the initial relative vorticity of the inflow. When inflow had initially large negative vorticity, the flow gained more negative vorticity due to deepening of the bottom (stretching) and then turned right after entering the JES. The inflow then followed the path of the Tsushima Warm Current along the coast of Japan. When the inflow was strong, with a speed in excess of 55 cm/s and with a large positive vorticity, potential vorticity appeared to be conserved. In this case, the EKWC followed isobaths along the coast and then left the coast, following topographic features north of Ulleung-Do. The northward flowing jet developed inertial meandering after leaving the coast, which is a characteristic of many western boundary currents. The regular, bimonthly deployments of drifters in the western portion of the Korea Strait revealed that splitting or branching of the flow through the western channel of the Korea Strait occurred only 15% of the time. And splitting or branching rarely occurred during the fall and winter seasons, when the inflow splitting was previously reported in hydrographic surveys. The time-averaged circulation map of the EKWC and its seaward extension were considerably enhanced by using regularly sampled geostrophic velocities calculated from sea level anomalies to remove biases in the mean velocity that were caused by irregular spatial and temporal drifter observations. The East Korean Warm Current, a mean coastal current along the Korean coast, behaved like the simple model by Arruda et al. (2004) in which the generation of the Ulleung Warm Eddy and the meandering circulation pattern were well reproduced.