2006년과 2007년 여름에 관측한 Hawaii-Chuuk 사이의 물리특성

신창웅,김동국,전동철,김응 한국해양과학기술원 2011 Ocean and Polar Research Vol.33 No.3

To investigate the physical characteristics and variations of oceanic parameters in the tropical central North Pacific, oceanographic surveys were carried out in summer of 2006 and 2007. The survey periods were classified by Oceanic Niño Index as a weak El Niño in 2006 and a medium La Niña in 2007. The survey instruments were used to acquire data on CTD (Conductivity Temperature and Depth), XBT (Expendable Bathythermograph), and TSG (Thermosalinograph). The dominant temporal variation of surface temperature was diurnal. The diurnal variation in 2007, when the La Niña weather pattern was in place, was stronger than that in 2006. Surface salinity in 2006 was affected by a northwestward branch of North Equatorial Current, which implies that the El Niño affects surface properties in the North Equatorial Current region. Two salinity minimum layers existed at stations east of Chuuk in both year's observations. The climatological vertical salinity section along 180oE shows that the two salinity minimum layers exist in 2oN~12oN region, consistent with our observations. Analysis of isopycnal lines over the salinity section implies that the upper salinity minimum layer is from intrusion of the upper part of North Pacific Intermediate Water into the lower part of South Pacific Subtropical Surface Water and the lower salinity minimum layer is from Antarctic Intermediate Water.

동해 남부 연안용승지수의 변화

신창웅,SHIN, CHANG-WOONG 한국해양학회 2019 바다 Vol.24 No.1

동해 남서부 해역의 해양생태계에 큰 영향을 미치는 연안용승의 변화를 파악하기 위해 1948년 1월부터 2018년 9월까지의 NCEP/NCAR 재분석자료를 이용하여 용승지수를 계산하였다. 평균 용승지수는 4월부터 8월까지 용승이 발생하는 양의 값이 보이며 7월에 최대 값이 나타났다. 용승지수의 장기 변화는 6월과 7월에 통계적으로 유의미한 감소추세가 나타났으며, 5, 6, 7월 용승지수의 합도 통계적으로 유의미한 감소 경향을 보였다. 한반도 주변의 대기압 분석을 통하여 용승지수의 변화 추세는 동해남부해역을 기준으로 북서쪽 영역($35-50^{\circ}N$, $114-129^{\circ}E$)의 기압 변화 추세의 영향이라는 것을 밝혔다. 최근 7년간(2012년-2018년)의 용승지수 분석결과 2017년 7월에 용승지수가 표준편차의 3배 이상 높은 것을 발견하였다. 이것은 중국 북동쪽 지방에 평년과 다르게 저기압이 발달하였고 북태평양고기압이 일본과 대만 사이까지 영향을 주어 동해 남부에 큰 기압 차이가 발생했기 때문이었다. 반면에 평년에 비하여 북쪽의 저기압과 남쪽의 고기압의 영향이 적었던 2018년 7월은 용승지수가 음의 값이었다. 동해남부 연안용승지수는 기후변화에 따라 감소하는 경향을 보이고 경년변동이 커서 생태환경에 대한 영향을 파악하기 위해서는 지속적인 모니터링이 필요하다. Long-term trends and recent variations of upwelling index (UI), which affects significantly ecosystem in southwestern part of the East Sea, were investigated. The UI was calculated with the NCEP/NCAR reanalysis data from January 1948 to September 2018. The mean UI has positive value that causes upwelling in April to August with a peak in July. The long-term reducing trend of UI was in statistically significant in June and July, and the sum of UI in May, June and July also showed same result. Through the atmospheric pressure analysis around the Korean peninsula, it was found that the trend of the UI was the influence of the pressure change trend in the northwestern region ($35-50^{\circ}N$, $114-129^{\circ}E$) of the southwestern part of the East Sea. Investigating UI in recent 7 years from 2012 to 2018, it was revealed that the UI was bigger than 3 times of standard deviation in July 2013. This was result from the sea level pressure difference became larger in the southwestern part of the East Sea than normal year due to the lowered air pressure in the northeastern region of China and the strengthened high air pressure of western peripheral of the North Pacific High. On the other hand, the UI in July 2018 was negative when the impact of the North Pacific High and the low air pressure in the northeastern China was weak. Due to the decreasing trend of UI and its large year-to-year variation in southwestern part of the East Sea, continuous monitoring is necessary to know the influence of coastal upwelling on the ecosystem.

Seasonal Variations in the Low-salinity Intermediate Water in the Region South of Sub-polar Front of the East Sea (Sea of Japan)

신창웅,변상경,김철수,이재학,김봉채,황상철,승영호,신홍렬 한국해양과학기술원 2013 Ocean science journal Vol.48 No.1

Seasonal variations in the low-salinity intermediate water (ESIW) in the region south of the sub-polar front of the East Sea were investigated by using historical hydrographic data. The salinity of the representative density (sigma-0=27.2) of the ESIW was minimal in summer and maximal in winter in the region south of the sub-polar front. The selected four subregions showed different salinity variations. In the west of Oki Spur and the Yamato Basin, salinity fluctuated similarly, with a minimum during summer. In the Ulleung Basin and northwest of Sado Island, however, variations in salinity showed two minima, one is in winter and the other is in summer. These results imply differences in the flow path of the ESIW into the region south of the sub-polar front over time.

동해중층수의 일반적인 분포

신창웅,변상경,김철수,이재학,김봉채,황상철,승영호,신홍렬 한국해양과학기술원 2007 Ocean and Polar Research Vol.29 No.1

To obtain the overall distribution patterns and characteristics of the East Sea Intermediate Water(ESIW), the historical data obtained by the Japan Maizuru Marine Observatory (MMO) and the Korea Ocean Research and Development Institute (KORDI) were analyzed. To obtain water characteristics of the ESIW on isopycnal surfaces, temperature, salinity and dissolved oxygen were interpolated at every 0.01 interval of potential density. And then the interpolated values were averaged at the same potential density. This potential density average method preserved the salinity minimum layer more clearly compared to the depth average method. The potential density (σθ) range of the ESIW was 26.9~27.3. The representative potential density of the ESIW was found to be 27.2, because the characteristics of the ESIW was clear at this density. From the horizontal distributions of physical properties on the isopycnal surface of 27.2σθ it is suggested that the low salinity ESIW circulates anticlockwise over the whole basin with the high salinity intermediate water. The low salinity intermediate water extended from the northwestern part to the east along the sub-polar front and to the Ulleung Basin along the east coast of Korea.

Southwestward Intrusion of Korea Strait Bottom Cold Water Observed in 2003 and 2004

신창웅,전동철,김철수,변상경,황상철 한국해양과학기술원 2006 Ocean science journal Vol.41 No.4

Hydrographic surveys were carried out four times in the western channel of the Korea Strait in March and August 2003 and in June and November 2004. The bottom cold water, which was lower than 10C, appeared in the channel trough except in March 2003. It flowed southwestward along the shelf of Korean coasts in August 2003 and in November 2004. The width and the maximum speed of the intrusion current were about 20 km and approximately 25 cms-1, respectively, off Ulsan, Korea. The volume transport of the bottom cold water was estimated 0.019 Sv (Sv106 m3 s-1) in August 2003 and 0.026 Sv in November 2004.

The Inflow Path of the East Sea Intermediate Water into the Ulleung Basin in July 2005

신창웅 한국해양과학기술원 2006 Ocean and Polar Research Vol.28 No.2

To investigate inflow path of the East Sea Intermediate Water (ESIW) into the Ulleung Basin, hydrographic data surveyed in July 2005 were analyzed. The ESIW was characterized by the Salinity Minimum Layer (SML) within a depth range of 100 to 360 meters. Averaged potential temperature and salinity of the SML were 1.835oC and 34.049 psu, respectively. Mean potential density () of the SML was 27.221 with a standard deviation of 0.0393. On isopycnal surfaces of 27.14 and 27.18 which correspond to upper layers of the ESIW, the coastal low salinity water was separated from the offshore low salinity water by the relatively warm and saline water which might be affected by the Tsushima Warm Current Water. Relatively cold and fresh water, however, intruded into the Ulleung Basin from the region of Korean coast on isopycnal surfaces of 27.22 and 27.26 which was lower layer of the ESIW. The salinity distribution in the isopycnal layer of 27.14~27.26 with acceleration potential on 27.22 surface also showed clearly that the low salinity water flowed from the coastal area and intruded into the Ulleung Basin. This implies that the ESIW flows from the north to the south along the east coasts of Korea and spreads into the Ulleung Basin in summer.

2006년과 2007년 여름에 관측한 Hawaii-Chuuk 사이의 물리특성

신창웅,김동국,전동철,김응,Shin, Chang-Woong,Kim, Dong-Guk,Jeon, Dong-Chull,Kim, Eung 한국해양과학기술원 2011 Ocean and Polar Research Vol.33 No.suppl3

To investigate the physical characteristics and variations of oceanic parameters in the tropical central North Pacific, oceanographic surveys were carried out in summer of 2006 and 2007. The survey periods were classified by Oceanic Ni$\tilde{n}$o Index as a weak El Ni$\tilde{n}$o in 2006 and a medium La Ni$\tilde{n}$a in 2007. The survey instruments were used to acquire data on CTD (Conductivity Temperature and Depth), XBT (Expendable Bathythermograph), and TSG (Thermosalinograph). The dominant temporal variation of surface temperature was diurnal. The diurnal variation in 2007, when the La Ni$\tilde{n}$a weather pattern was in place, was stronger than that in 2006. Surface salinity in 2006 was affected by a northwestward branch of North Equatorial Current, which implies that the El Ni$\tilde{n}$o affects surface properties in the North Equatorial Current region. Two salinity minimum layers existed at stations east of Chuuk in both year's observations. The climatological vertical salinity section along $180^{\circ}E$ shows that the two salinity minimum layers exist in $2^{\circ}N{\sim}12^{\circ}N$ region, consistent with our observations. Analysis of isopycnal lines over the salinity section implies that the upper salinity minimum layer is from intrusion of the upper part of North Pacific Intermediate Water into the lower part of South Pacific Subtropical Surface Water and the lower salinity minimum layer is from Antarctic Intermediate Water.

Current Structure and Volume Transport in the Jeju Strait Observed for a Year with Multiple ADCP Moorings

신창웅,민홍식,이석,강현우,구본화,김동국,박준성,권순열,최병주 한국해양과학기술원 2022 Ocean science journal Vol.57 No.3

The seasonal and spatial variation of the current structure and volume transport across the Jeju Strait (JS) is described based on an analysis of the data from five bottom mounted acoustic Doppler current profilers from February 13, 2020 to February 23, 2021. The current was weak and the mixed layer was well developed in winter, so the vertical current shear was not large. Whereas in summer, the inflow of high-temperature and low-salinity surface water built up the stratification, and the surface current velocity increased, resulting in a large vertical current shear. One salient feature to be found was that a westward flowing counter current in the lower layer appeared from June to December near the bottom trough of the JS. We named this seasonal counter current in the lower layer the Jeju Strait Under Current. The eastward net volume transport passing through the JS was large in summer–autumn and small in winter-spring, but did not follow a simple sinusoidal pattern. The annual mean net volume transport was 0.48 Sv (Sv ≡ 106 m3 s−1), with a minimum (0.27 Sv) in December and a maximum (0.79 Sv) in October 2020. When there were strong northerly winds in winter, a net volume transport to the west was temporarily caused by Ekman transport, but the direction reverted to the east as soon as the northerly winds lessened. When there were strong northwesterly (southeasterly) winds due to typhoons, the volume transport decreased (increased) sharply and then recovered rapidly.

Characteristics of a Warm Eddy Observed in the Ulleung Basin in July 2005

신창웅 한국해양과학기술원 2009 Ocean and Polar Research Vol.31 No.4

Oceanographic survey data were analyzed to understand the characteristics of a warm eddy observed in the Ulleung Basin in July 2005. The temperature distribution at 200 db and vertical sections provided evidence of the warm eddy in the Ulleung Basin (UWE05). Based on the 5℃ isothermal line on 200 db temperature, the major axis was 160 km from southwest to northeast, and the minor axis was 80 km from southeast to northwest. The homogeneous layer in the thermocline of UWE05 had mean values of 10.40℃ potential temperature, 34.35 psu salinity, and 26.37 kg/m3 potential density (σθ) and provided evidence that UWE05 also existed during the winter of 2004-2005. A warm streamer initially flowed along the circumference of UWE05 and mixed with the upper central water. Two northward current cores were found on the western side of the measured current section at the central latitude of UWE05. One was the East Korean Warm Current (EKWC) and the other was the main stream of the western part of UWE05. Geostrophic transport of the upper layer (from the surface to the isopycnal surface of 26.9 σθ) was approximately 2.5 Sv in the eastern side of UWE05. However, the measured transport was twice as large as the geostrophic transport. Mass conservation of geostrophic transport was well satisfied in the upper layer. The direct current measurements and geostrophic transport analysis showed that the EKWC meandered around UWE05. Oceanographic survey data were analyzed to understand the characteristics of a warm eddy observed in the Ulleung Basin in July 2005. The temperature distribution at 200 db and vertical sections provided evidence of the warm eddy in the Ulleung Basin (UWE05). Based on the 5℃ isothermal line on 200 db temperature, the major axis was 160 km from southwest to northeast, and the minor axis was 80 km from southeast to northwest. The homogeneous layer in the thermocline of UWE05 had mean values of 10.40℃ potential temperature, 34.35 psu salinity, and 26.37 kg/m3 potential density (σθ) and provided evidence that UWE05 also existed during the winter of 2004-2005. A warm streamer initially flowed along the circumference of UWE05 and mixed with the upper central water. Two northward current cores were found on the western side of the measured current section at the central latitude of UWE05. One was the East Korean Warm Current (EKWC) and the other was the main stream of the western part of UWE05. Geostrophic transport of the upper layer (from the surface to the isopycnal surface of 26.9 σθ) was approximately 2.5 Sv in the eastern side of UWE05. However, the measured transport was twice as large as the geostrophic transport. Mass conservation of geostrophic transport was well satisfied in the upper layer. The direct current measurements and geostrophic transport analysis showed that the EKWC meandered around UWE05.

KOGA 기획과 활용연구

신창웅,박광순,노영재,장경일,방익찬,문일주,김태림,김봉채,김동선,김광희,김기완,노태근,임관창 한국해양과학기술원 2010 Ocean and Polar Research Vol.32 No.3

In late 2010, the Korea Hydrographic and Oceanographic Administration proposed a national monitoring project involving the deployment of 8 realtime ocean data buoys. The area occupied by the buoy-array, located south of the Ieodo Ocean Research Station, can be regarded as a kind of gateway to Korean waters with respect to warm currents and the shipping industry. The acronym for the project, KOGA (Korea Ocean Gate Array) was derived from this aspect. To ensure the success of the project, international cooperation with the neighboring countries of China and Japan is highly desirable. Once KOGA is successfully launched and the moored buoys start to produce data, the data will be applied to various areas such as data assimilation for operational oceanography, circulation dynamics, biogeochemical studies,satellite observations, and air-sea interactions. The aim of this paper is to provide suggestions for KOGA planning and applications.