• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.418-421
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• 2007

Using gridded wind-stress products constructed by satellite scatterometers (ERS-1, 2 and QSCAT) data and those by numerical weather prediction(NWP) model(NCEP-reanalysis), we estimate wind-driven transports of the North Pacific subtropical gyre, and compare them in the central portion of the gyre (around 300 N) with geostrophic transports calculated from historical hydrographic data (World Ocean Database 2005). Even if there are some discrepancies between the wind-driven transports by the QSCAT and NCEP products, they are both in good agreement with the geostrophic transports within reasonable errors, except for the regional difference in the eastern part of the zone. The difference in the eastern part is characterized by an anticyclonic deviation of the geostrophic transport resulting from an anti-cyclonic anomalous flow in the surface layer, suggesting that it is related to the Eastern Gyral produced by the thermohaline process associated with the formation of the Eastern Subtropical Mode Water. We also examine the consistency of the Sverdrup transports estimated from these products by comparing them with the transports of the western boundary current, namely the Kuroshio regions, in previous studies. The net southward transport, based on the sum of the Sverdrup transports by QSCAT and NCEP products and the thermohaline transport, agrees well with the net northward transport of the western boundary current, namely the Kuroshio transport. From these results, it is concluded that the Sverdrup balance can hold in the North Pacific subtropical gyre.

• Journal of the korean society of oceanography
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• v.37 no.3
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• pp.134-143
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• 2002

Using OGCM results, we have shown that the ring-like cold baroclinic eddies associated with cyclonic circulation are shed from late summer to early fall near the Izu-Ogasawara Ridge from the Kuroshio Extension owing to baroclinic instability. On the other hand, warm baroclinic eddies are generated by the intensified western boundary current associated with the warm anomaly accumulated near the Ridge in winter, which corresponds to the basin-wide barotropic intensification of the wind-driven gyre in winter. We are successful in reproducing the behavior of those meso-scale eddies using a simple two-layer primitive equation model driven by seasonal winds associated with the positive curl. Those eddies carry barotropic seasonal signals originated in the Pacific Basin quite slowly west of the ridge; this process introduces a phase lag in the timing of the seasonal maximum transport in the Philippine Basin west of the ridge. It Is demonstrated that the existence of bottom topography, baroclinicity, and nonlinearity due to advection are three necessary elements for the generation of these eddies south of Japan.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.52-53
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• 2005

Time series of gridded surface wind and wind-stress vectors over the world ocean have been constructed by satellite scatterometer data. The products are derived from the ERS-l,2 covering 9 years during 1992-2000 and the Sea Winds on board QuikSCAT (Qscat) which has been operating up to the present since June 1999, so they allows us to analyze variabilities with various time scales. In this study, we focus on interannual variability of the wind stress in the mid- and high-latitude region of North Pacific. These are compared with those by numerical weather prediction(NWP) ones (NCEP Reanalysis). We also examine variability in the wind-stress curl field that is an important factor for ocean dynamics and focus its time and spatial characters in the northwestern Pacific around Japan. It is found that the vorticity field in the lower atmosphere tends to increase gradually with time, suggesting the enhancement of the North Pacific subtropical gyre.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.133-136
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• 2006

The mesoscale eddy field in the North Pacific Ocean, simulated by a high resolution eddy-resolving OGCM ($1/12^{\circ}C$ horizontal resolution), was analyzed, and compared with satellite altimetry data of TOPEX/Poseidon. High levels of eddy kinetic energy (EKE) appear near the Kurosho, North Equatorial Current (NEC), and Subtropical Countercurrent (STCC) in the western part of the subropical gyre. In particlure, it was found that the EKE level of the STCC has a well-defined annual cycle, but no distinct annual cycle of the EKE exists in any other zonal current of the North Pacific Ocean.

• Ocean and Polar Research
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• v.30 no.3
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• pp.335-345
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• 2008

In order to study spatial variabilities and major controlling factors, we measured fugacity of $CO_2(fCO_2)$, temperature, salinity and nutrients in surface waters of the North Pacific($7^{\circ}30'{\sim}33^{\circ}15'N$, $123^{\circ}56'E{\sim}164^{\circ}24'W$) between September$\sim$October 2007. The North Pacific and the marginal sea were distinguished by $fCO_2$ distribution as well as unique characteristics of temperature and salinity. There was a distinct diurnal SST variation in the tropical North Pacific area, and surface $fCO_2$ coincidently showed diurnal variation. In the North Pacific area, surface $fCO_2$ was mainly controlled by temperature, while in the marginal sea area it was primarily dependent on alkalinity and dissolved inorganic carbon concentrations. Air-sea $CO_2$ flux showed a large spatial variation, with a range of $-6.10{\sim}5.06\;mmol\;m^{-2}day^{-1}$. The center of subtropical gyre of North Pacific acted as a source of $CO_2(3.09{\pm}0.95\;mmol\;m^{-2}day^{-1})$. Tropical western North Pacific (i.e. the 'warm pool' area and the subtropical western North Pacific) acted as weak sources of $CO_2$($1.07{\pm}1.20\;mmol\;m^{-2}day^{-1}$ and $0.50{\pm}0.53\;mmol\;m^{-2}day^{-1}$, respectively). In the marginal sea, however, the flux was estimated to be $-0.68{\pm}1.17\;mmol\;m^{-2}day^{-1}$, indicating that this area acted as a sink for $CO_2$.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.3
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• pp.439-447
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• 2019

Some dynamical issues about the Tsushima Warm Current (TWC) are reviewed and checked for the remaining unresolved problems, focusing on the formation of the TWC, seasonal variation of its volume transport and its branching in the East Sea. The TWC is a part of the North Pacific (NP) subtropical gyre driven by the NP global wind system. However, the quantitative amount of volume transport is sensitive to friction, basin geometry, barrier effect and so on. Among many causes suggested by many scientists, subpolar winds are found to be most closely related with the seasonal variation of TWC volume transport. However, more studies relating the latter not only to the subpolar winds but also to those including the subtropical winds seem to be required. The branching of the TWC has been known to be due to the western intensification for the East Korean Warm Current (EKWC) and to the bottom trapping for the Nearshore Branch. Since the former hypothesis is problematic in explaining the seasonal variation of the EKWC, other candidate mechanisms may need to be considered.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.4
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• pp.291-306
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• 2021

From the climate change scenario experiments of 21 models participating in Coupled Climate Model Inter-comparison Project Phase 6, future changes of sea surface temperature (SST) and Kuroshio in the Northwest Pacific were analyzed. The spatial feature of SST change was found to be related to the change of the current speed and spatial distribution of Kuroshio. To investigate the relationship between the change in latitude of the Kuroshio extension region, which flows along the boundary between the subtropical gyre and the subarctic gyre in the North Pacific, and the large-scale atmospheric circulation due to global warming, the zero-windstress curl line for each climate change experiment from 9 out of 21 models were compared. As the atmospheric radiative forcing increases due to the increase of greenhouse gases, it was confirmed that the zero-windstress curl line moves northward, which is consistent with the observation. These results indicate that as the Hadley Circulation expands to the north due to global warming, the warming of the mid-latitudes to which the Korean Peninsula belongs may be accelerated. The volume transport and temperature of the Tsushima Warm Current flowing into the East Sea through the Korea Strait also increased as the atmospheric radiative forcing increased.

• Ocean and Polar Research
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• v.38 no.2
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• pp.89-102
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• 2016

In this study, we evaluated the model performance with respect to Sea Surface Temperature (SST) and Net Heat Flux (NHF) by considering the characteristics of seasonal temperature variation and contributing factors and by analyzing heat budget terms in the Northwestern Pacific and East Asian Marginal Seas ($110^{\circ}E-160^{\circ}E$, $15^{\circ}N-60^{\circ}N$) using the HadGEM2-AO historical run. Annual mean SST of the HadGEM2-AO is about $0.065^{\circ}C$ higher than observations (EN3_v2a) from 1950 to 2000. Since 1960, the model has simulated well the long-term variation of SST and the increasing rate of SST in the model ($0.014^{\circ}C/year$) is comparable with observations ($0.013^{\circ}C/year$). Heat loss from the ocean to the atmosphere was simulated slightly higher in the HadGEM2-AO than that in the reanalysis data on the East Asian Marginal Seas and the Kuroshio region. We investigated the causes of temperature variation by calculating the heat budget equation in the two representative regions. In the central part of the Kuroshio axis ($125^{\circ}E-130^{\circ}E$, $25^{\circ}N-30^{\circ}N$: Region A), both heat loss in the upper mixed layer by surface heat flux and vertical heat advection mainly cause the decrease of heat storage in autumn and winter. Release of latent heat flux through the heat convergence brought about by the Kuroshio contributes to the large surface net heat flux. Positive heat storage rate is mainly determined by horizontal heat advection from March to April and surface net heat flux from May to July. In the central part of the subtropical gyre ($155^{\circ}E-160^{\circ}E$, $22^{\circ}N-27^{\circ}N$: Region B), unlike Region A, vertical heat advection predominantly causes the decrease of heat storage in autumn and winter. In spring and summer, surface heat flux contributes to the increase of heat storage in Region B and the period is two times longer than the period for Region A. In this season, shoaling of the mixed layer depth plays an important role in the increase of SST.