• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.3
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• pp.295-306
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• 2003

Recently efforts are underway to analyze the impacts of anthropogenic $CO_2$ on the global environments and the amount of oceanic uptake increase. The East Sea is now viewed as a miniature ocean because its circulation pattern is similar to the ocean conveyer belt. The biological pump of the East Sea is a vital component to understand the carbon cycle quantitatively. In this paper, the biological pump is estimated utilizing the stoichiometric ratio between carbon and phosphorus. A simple phosphate budget model is constructed based on the seawater and dissolved oxygen box model that can simulate the recent structural change in deep water circulation of the East Sea. A model run from you 1952 to 2040 shows the steadily intensifying biological pump. Currently it exports about 0.016 Pg C yr$^{-1}$ , which corresponds to 35％ of the carbon introduced into the seawater by the air-sea exchange. An increased oxygen supply to the central water mass as a result of from the transition in the ventilation system might enhance the remineralization of sinking biogenic particles. This should strengthen the upward nutrient flux into the surface layer. Consequently, the biological sequestration of anthropogenic carbon is expected to increase with time. The estimated biological uptake of the anthropogenic carbon in the East Sea since the Industrial Revolution is estimated as 0.025 Pg C.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.587-601
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• 2020

The ocean circulation was simulated in the East Sea and Ulleungdo-Dokdo region using ROMS (Regional Ocean Modeling System) model. By adopting the East Sea 3 km model and the HYCOM 9 km data, Ulleungdo 1 km model and Ulleungdo-Dokdo 300 m model were constructed with one-way grid nesting method. During the model development, a correction method was proposed for the distortion of the open boundary data which may be caused by the bathymetry data difference between the mother and child models and the interpolation/extrapolation method. Using this model, a super-high resolution ocean circulation with a horizontal resolution of 300 m near the Ulleungdo and Dokdo region was simulated for year 2018. In spite of applying the same conditions except for the initial and boundary data, the numerical models result indicated significantly different characteristics in the study area. Therefore, these results were compared and verified by using the surface current data estimated by satellites altimeter data and temperature data from NIFS (National Institute of Fisheries Science). They suggest that in general, the improvement of the one-way grid nesting with the HYCOM data on RMSE, Mean Bias, Pattern correlation and Vector correlation is greater in 300 m model than in the 1 km model. However, the nesting results of using East Sea 3 km model showed that simulations of the 1 km model were better than 300 m model. The models better resolved distinct ridge/trough structures of isotherms in the vertical sections of water temperature when using the higher horizontal resolution. Furthermore, Karman vortex street was simulated in Ulleungdo-Dokdo 300 m model due to the terrain effect of th islands that was not shown in the Ulleungdo 1 km model.

• Ocean Science Journal
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• v.41 no.1
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• pp.1-10
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• 2006

Total sea surface temperature (SST) in a coupled GCM is diagnosed by separating the variability into signal variance and noise variance. The signal and the noise is calculated from multi-decadal simulations from the COLA anomaly coupled GCM and the interactive ensemble model by assuming both simulations have a similar signal variance. The interactive ensemble model is a new coupling strategy that is designed to increase signal to noise ratio by using an ensemble of atmospheric realizations coupled to a single ocean model. The procedure for separating the signal and the noise variability presented here does not rely on any ad hoc temporal or spatial filter. Based on these simulations, we find that the signal versus the noise of SST variability in the North Pacific is significantly different from that in the equatorial Pacific. The noise SST variability explains the majority of the total variability in the North Pacific, whereas the signal dominates in the deep tropics. It is also found that the spatial characteristics of the signal and the noise are also distinct in the North Pacific and equatorial Pacific.

• Ocean and Polar Research
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• v.37 no.2
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• pp.149-159
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• 2015

The Southern Ocean (SO) plays a primary role in global climate by storing and transporting anthropogenic carbon dioxide through the meridional overturning circulation and the biological pumping process. In this study, we aim to investigate interannual variability of summer chlorophyll concentration in the SO and its relation with the El $Ni{\tilde{n}}o$ Southern Oscillation (ENSO), using satellite ocean color data covering 16 years from 1997 to 2012. During El $Ni{\tilde{n}}o$ periods, chlorophyll concentration tends to increase in the subtropics (north of the subantarctic front). This chlorophyll increase is likely linked to El $Ni{\tilde{n}}o$-induced surface cooling that increases nutrient supply through enhanced vertical mixing in the subtropics. On the other hand, the subpolar gyres show localized chlorophyll changes in response to the ENSO. The localized response seems to be primarily attributed to changes in sea-ice concentrations. Our findings suggest that ENSO contributes interannual variability of chlorophyll in the SO through different mechanisms depending on regions.

• Atmosphere
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• v.24 no.2
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• pp.189-196
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• 2014

The definition of onset date of Changma is revisited in this study using a quality controlled Ieodo ocean research station data. The Ieodo station has great importance in terms of its southwest location from Korean Peninsula and, hence, makes it possible to predict Changma period in advance with less impact of continents. The onset date of Changma using the Ieodo station data is defined by the time that meridional wind direction changes and maintains from northerly to southerly, and then the zonal wind changes from easterly to westerly after first June. This definition comes from a recognition that the establishment and movement of the western North Pacific subtropical high (WNPSH) cause Changma through southwesterly flow. The onset data of Changma has been determined by large-scale dynamic-thermodynamic characteristics or various meteorological station data. However, even the definition based on circulation data at the Ieodo station has a potential for the improved prediction skill of the onset date of Changma. The differences between before and after Changma, defined as Ieodo station data, are also found in synoptic chart. The convective instability and conspicuous circulations, corresponding low-level southwesterly flow related to WNPSH and strong upper-level zonal wind, are represented during Changma.

• Ocean and Polar Research
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• v.39 no.3
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• pp.169-179
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• 2017

The "GeoDrifter" is a newly-developed surface drifter with high temporal resolution. It is the first time that high-frequency drifters have been deployed in the East/Japan Sea. The purpose of this study is to introduce the phenomena experienced by these drifters flowing along with the Tsushima Current across the East/Japan Sea, focusing on high-frequency variability, and to discuss them in comparison with previous observations. The observed basin-scale circulation of the Tsushima Current generally coincides well with the known schematic circulation. The GeoDrifter trajectories also show inertial oscillations almost everywhere in the oceanic regions of the East/Japan Sea, strong semi-diurnal tidal currents in the western part of Korea Strait, diurnal currents much stronger than semi-diurnal currents in the upstream region of the Nearshore Branch off the Japanese coast, and many warm eddies in the Yamato Basin, all comparable to the observational results reported in the previous studies. An interesting point is that the semi-diurnal tidal currents undergo a great spatial variation in the western part of the Korea Strait. The observed features that cannot be explained are, among others, strong counter-clockwise motions with oscillating period about 51 hours appearing in the upstream region of the Nearshore Branch off the Japanese coast and the different tidal behaviors between upstream and downstream regions of the latter.

• Atmosphere
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• v.27 no.3
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• pp.277-290
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• 2017

Characteristics of precipitation in South Korea during the 2016 Changma period (6/18~7/30) are analyzed in great details. El $Ni{\tilde{n}}o$-induced tropical Indian Ocean (IO) basin-wide warming lasts from spring to early summer and induces the western North Pacific subtropical high (WNPSH) circulation anomaly through an equatorial Kelvin wave during the 2016 Changma period. Along the northern edge of the WNPSH, strong precipitation occurred, in particular, over eastern China and southern Japan. During the Changma period, South Korea had the near-normal mean precipitation amount (~332 mm). However, about 226 mm of rain fell in South Korea during 1 July to 6 July, which amounts to 67% of total Changma precipitation in that year. Upper-level synoptic migratory lows and low-level moisture transport played an essential role, especially from 1 July to 3 July, in triggering an abrupt development of fronts over the Korean Peninsula and the eastern continent China. The front over the eastern China migrates progressively eastward, which results in heavy rainfall over the Korean peninsula from 1 to 3 July. In contrast, from 4 to 6 July, the typhoon (NEPARTAK) affected an abrupt northward advance of the North Pacific subtropical high (NPSH). The northward extension of the NPSH strengthens the Changma front and induces the southerly flows toward the Korean peninsula, giving rise to an increase in heavy rainfall. The NEPARTAK is generated due to interaction of the Madden-Julian Oscillation (MJO), equatorial Rossby wave and Kelvin waves.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.181-190
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• 2010

In case of constructing submerged breakwaters, the circulation current is occurred around the open inlet because of mean water level difference between front and rear sides of them. The aim of this study is to investigate the flow control structure of new-type submerged breakwater which is able to reduce mean water level at rear side of it. At first, the numerical model (LES-WASS-3D) is validated by comparing with existing experimental data. And then, numerical simulation is carried out to examine wave height, mean water level and mean flow around the newtype submerged breakwater. From the numerical results, it can be pointed out that the new-type submerged breakwater with drainage system reduces the rip current around the open inlet.

• Ocean and Polar Research
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• v.24 no.3
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• pp.227-236
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• 2002

For ten firn cores, from both the eastern and the western side of Lambert Glacier basin (LGB), snow accumulation rate and isotopic temperature were measured far the recent 50 years. Results show that snow accumulation for five cores over the eastern side of LGB (GC30, GD03, GD15, DT001, and DT085) at Wilks Land and Princess Elizabeth Land increases, whereas it decreases at the western side (Core E, DML05, W200, LGB 16, and MGA) at Dronning Maud Land, Mizuho Plateau and Kamp Land. For the past decades, the increasing rate was $0.34-2.36kg\;m^{-2}a^{-1}$ at the eastern side and the decreasing rate was $-0.01\;-\;-2.36kg\;m^{-2}\;a^{-1}$ at the western side. Temperatures at the eastern LGB were also increased with the rate of $0.02%o\;a^{-l}$. At the western LGB it was difficult to see clear trends, which were confirmed by Instrumental temperature records at coastal stations. Although statistic analysis and modeling results display that both surface temperature and accumulation rate has increased trends in Antarctic ice sheet during 1950-2000, the regional distributions were much more different for different geographic areas. We believe that ice-core records at Wilks Land and Princess Elizabeth Land reflect the real variations of SST and moisture change in the southern India Ocean. For the Kamp Land and Dronning Maud Land, however circulation pattern was different, by which the climate was more complicated. The International Trans-Antarctic Scientific Expedition (ITASE) aimed to reveal an overall spatial pattern of climate change over Antarctic ice sheet for the past 200 years. This study points the importance of continental to regional circulation to annual-decadal scale climate change in Antarctica.

• Ocean Science Journal
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• v.42 no.3
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• pp.153-163
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• 2007

This study is based on a series of numerical modeling experiments to understand the tidal circulation in the Kangjin Bay (KB). The tidal circulation in the KB is mostly controlled by the inflow from two channels, Noryang and Daebang which introduce the open ocean water into the northern part of the KB with relatively strong tidal current, while in the southern part of the KB, shallowest region of the entire study area, weak tidal current prevails. The model prediction of the sea level agrees with observed records at skill scores exceeding 90 % in terms of the four major tidal constituents (M2, S2, K1, O1). However, the skill scores for the tidal current show relatively lower values of 87, 99, 59, 23 for the semi-major axes of the constituents, respectively. The tidal ellipse parameters in the KB are such that the semi-major axes of the ellipse for M2 range from 1.7 to 38.5 cm/s and those for S2 range from 0.5 to 14.4 cm/s. The orientations of the major-axes show parallel with the local isobath. The eccentricity values at various grid points of ellipses for M2 and S2 are very low with 0.2 and 0.06 on the average, respectively illustrating that the tidal current in the KB is strongly rectilinear. The magnitude of the tidal residual current speed in the KB is on the order of a few cm/s and its distribution pattern is very complex. One of the most prominent features is found to be the counter-clockwise eddy recirculation cell at the mouth of the Daebang Channel.