Wind-induced Spatial and Temporal Variations in the Thermohaline Front in the Jeju Strait, Korea

한인성,서영상,성기택 한국수산과학회 2013 Fisheries and Aquatic Sciences Vol.16 No.2

We investigated the short-term and local changes in the thermohaline front in the Jeju Strait, Korea, which is usually formed during winter and spring. To do so, we compared Real-Time Observation System by Ferryboat (RTOSF) data with wind data and routinely collected oceanographic data. During February and April 2007, a thermohaline front formed in the Jeju Strait around the 13-14°C isotherms and 33.0-33.5 isohalines. The thermohaline was clearly weakened and began moving southward in mid-March. The variations in the surface temperature and salinity showed a continuous north-south oscillation of the thermohaline front with a period of 3-10 days. The speed of the short-term and local fluctuation of thermohaline front was about 5-30 cm/s. We confirmed these findings by examining the variation in the maximum temperature gradient and 14°C isotherm during the study period. These short-term and local changes had not been previously detected using serial oceanographic and satellite data. Analysis of local wind data revealed a northerly wind fluctuation with a period of 3-10 days, which was clearly related to the short-term and local changes in the thermohaline front. The short-term and local changes of the thermohaline front in the Jeju Strait originated from local changes in the winter monsoon in this area.

Wind-induced Spatial and Temporal Variations in the Thermohaline Front in the Jeju Strait, Korea

Han, In-Seong,Suh, Young-Sang,Seong, Ki-Tack The Korean Society of Fisheries and Aquatic Scienc 2013 Fisheries and Aquatic Sciences Vol.16 No.2

We investigated the short-term and local changes in the thermohaline front in the Jeju Strait, Korea, which is usually formed during winter and spring. To do so, we compared Real-Time Observation System by Ferryboat (RTOSF) data with wind data and routinely collected oceanographic data. During February and April 2007, a thermohaline front formed in the Jeju Strait around the 13-$14^{\circ}C$ isotherms and 33.0-33.5 isohalines. The thermohaline was clearly weakened and began moving southward in mid-March. The variations in the surface temperature and salinity showed a continuous north-south oscillation of the thermohaline front with a period of 3-10 days. The speed of the short-term and local fluctuation of thermohaline front was about 5-30 cm/s. We confirmed these findings by examining the variation in the maximum temperature gradient and $14^{\circ}C$ isotherm during the study period. These short-term and local changes had not been previously detected using serial oceanographic and satellite data. Analysis of local wind data revealed a northerly wind fluctuation with a period of 3-10 days, which was clearly related to the short-term and local changes in the thermohaline front. The short-term and local changes of the thermohaline front in the Jeju Strait originated from local changes in the winter monsoon in this area.

A Conceptual Two-Layer Model of Thermohaline Circulation in a Pie-Shaped $\beta$-Plane Basin

Park, Young-Gyu The Korean Society of Oceanography 2003 Journal of the Korean Society of Oceanography Vol.38 No.1

The three dimensional structure of thermohaline circulation in a D-plane is investigated using a conceptual two layer model and a scaling argument. In this simple model, the water mass formation region is excluded. The upper layer represents the oceans above the main thermocline. The lower layer represents the deep ocean below the thermocline and is much thicker than the upper layer. In each layer, geostrophy and the linear vorticity balance are assumed. The cross interfacial velocity that compensates for the deep water mass formation balances downward heat diffusion from the top. From the above relations, we can determine the thickness of the upper layer, which is the same as thermocline depth. The results we get is basically the same as that we get for an f-plane ocean or the classical thermocline theory. Mass budget using the velocity scales from the scaling argument shows that western boundary and interior transports are much larger than the net meridional transport. Therefore in the thermohaline circulation, horizontal circulation is much stronger than the vertical circulation occuring on a meridional plane.

하계 동중국해 해양구조 및 식물플랑크톤 생물량의 공간적 분포특성

윤양호(Yang Ho Yoon),최임호(Im Ho Choi),서호영(Ho Yong Soh),황두진(Doo Jin Hwang) 전남대학교 수산과학연구소 2002 수산과학연구소논문집 Vol.11 No.-

We were carried out on the thermohaline structure and phytoplankton biomass, such as chlorophyll a in the East China Sea during early summer in 2001. As a results of water mass on T-S diagram, three characteristic water mass were identified. We are divide them into coastal water mass, cold water mass and oceanic water mass. The former are characterized by high temperature, low salinity and high Chl-a concentration originated China territory, the secondary are characterized by low temperature, high density and high Chl- a concentration originated bottom cold water of Yellow Sea, and the latter are high temperature, high salinity and low Chl-a concentration originated from Tsushima warm current, between them internal discontinuous layer was formed at the intermediate depth (about 20 ~30m and 45m layer). Phytoplankton biomass, such as chlorophyll a concentration in the East China Sea were controlled by the coastal waters of Chinese Continent.

Effect of Thermal Stratification and Mixing on Phytoplankton Community Structure in the Western Channel of the Korea Strait

Shon, Dong-Hyun,Shin, Kyoung-Soon,Jang, Pung-Guk,Kim, Young-Ok,Chang, Man,Kim, Woong-Seo Korea Institute of Ocean ScienceTechnology 2008 Ocean and Polar Research Vol.30 No.3

The profile of a fixed site at station M ($34.77^{\circ}N,\;129.13^{\circ}E$) in the Korea Strait was studied from March 2006 to February 2007. The aim was to understand the relationship between the annual thermal stratification pattern and seasonal variation in phytoplankton community structure. Physicochemical factors including temperature, salinity and nutrient concentrations, which strongly influence the proliferation and diversity of phytoplankton, were measured. The study period was divided into three due to the characteristic of thermohaline structures; mixed I (March-May 2006), stratified (June-November 2006) and mixed II(December 2006-Feburuary 2007). Diatoms dominated during the mixed I (89%) and II (48%) periods, while nanoplankton group occupied over 83% of total population during the stratified period. The dominant species during the mixed I and II was Chaetoceros socialis (47% and 29%, respectively), while during the stratified period Gyrodinium sp.(4%) was the most dominant. Averaged total chl a concentrations during the mixed I and II periods were 0.61 mg $m^{-3}$ and 0.72 mg $m^{-3}$, respectively, which were at least two-fold higher than that during the stratified period (0.30 mg $m^{-3}$). The vertical mixing and convection process of the water column induced nutrient supply from the bottom layer to the euphotic zone. It also led to the dominance of diatoms during the mixed periods, whereas small phytoplankton prevailed over large phytoplankton as stratification blocked the upward movement of nutrients to subsurface during the stratified period. During the mixed I and II periods, microplanktonic chl a dominated concentrations (50% and 48%, respectively), while picoplanktonic chl a occupied over 37% of total chl a during the stratified period.

Effect of Thermal Stratification and Mixing on Phytoplankton Community Structure in the Western Channel of the Korea Strait

손동현,신경순,장풍국,김영옥,장만,김웅서 한국해양과학기술원 2008 Ocean and Polar Research Vol.30 No.3

The profile of a fixed site at station M (34.77oN, 129.13oE) in the Korea Strait was studied from March 2006 to February 2007. The aim was to understand the relationship between the annual thermal stratification pattern and seasonal variation in phytoplankton community structure. Physicochemical factors including temperature, salinity and nutrient concentrations, which strongly influence the proliferation and diversity of phytoplankton, were measured. The study period was divided into three due to the characteristic of thermohaline structures; mixed I (March-May 2006), stratified (June-November 2006) and mixed II (December 2006-Feburuary 2007). Diatoms dominated during the mixed I (89%) and II (48%) periods, while nanoplankton group occupied over 83% of total population during the stratified period. The dominant species during the mixed I and II was Chaetoceros socialis (47% and 29%, respectively), while during the stratified period Gyrodinium sp. (4%) was the most dominant. Averaged total chl a concentrations during the mixed I and II periods were 0.61 mg m-3 and 0.72 mg m-3, respectively, which were at least two-fold higher than that during the stratified period (0.30 mg m-3). The vertical mixing and convection process of the water column induced nutrient supply from the bottom layer to the euphotic zone. It also led to the dominance of diatoms during the mixed periods, whereas small phytoplankton prevailed over large phytoplankton as stratification blocked the upward movement of nutrients to subsurface during the stratified period. During the mixed I and II periods, microplanktonic chl a dominated concentrations (50% and 48%, respectively), while picoplanktonic chl a occupied over 37% of total chl a during the stratified period.

하계 다도해 바다 목장 해역의 해양구조와 식물플랑크톤 군집의 공간적 분포특성

윤양호 ( Yang Ho Yoon ),고성정 ( Sung Chung Ko ) 한국수산경영기술연구원 2002 수산연구 Vol.17 No.-

The Impact of Southern Ocean Thermohaline Circulation on the Antarctic Circumpolar Current Transport

( Seong Joong Kim ),( Bang Yong Lee ) 대한지구물리학회 2006 지구물리 Vol.9 No.4

Cochlodinium polykrikoides 적조 발생시의 해양환경

이문옥(M. O. Lee),김병국(B. K. Kim),김종규(J. K. Kim) 한국해양환경·에너지학회 2015 한국해양환경·에너지학회 학술대회논문집 Vol.2015 No.5

국립수산과학원이 1993년부터 2013년까지 지난 20년간 우리나라 연안에서 관측한 정선 관측자료와 위성 영상자료를 분석하여, Cochlodinium polykrikoides(이하 C. polykrikoides)적조가 빈발하는 8월의 해양환경의 특징을 조사하였다. 매년 C. polykrikoides적조의 최초발생지로 알려진 고흥연안에서의 표층 수온은 19.5-27.3℃(평균 24.6℃)로, 거의 일정한 반면, 염분은 27.01-33.83(평균 31.11)로, 해가 갈수록 증가하는 경향을 보였다. 한편, C. polykrikoides 적조 발생시, 양쯔강 하구에 가장 가까운 정점 317-22(북위31.5°, 동경 124°)에서의 8월의 표층 수온은 고흥 연안보다 1.3-3.01℃ 정도 더 높았으나, 염분은 31.11 로, 고흥 연안과 거의 유사하였다. 또한, 하계 8월의 표층(0m) 에 있어서의 우리나라 남해안과 중국 양쯔강 하류를 포함한 동중국해 연안의 수평방향의 밀도(σt)분포를 검토한 결과, 대략 제주도를 중심으로 하여 한국 남해 연연수와 양쯔강 하천수의 영향을 받는 중국대륙 연안수와의 사이에 열염전선이 존재하는 것으로 판단되었다. 더욱이, 하계 C. polykrikoides 적조 발생시의 NOAA 및 NGSST 위성영상자료에 의하면, 양쯔강 하천수가 제주도와 우리나라 남해안까지 확장하여 영향을 주고 있는 것으로 생각된다. 즉, 이것은 하계 고흥을 비롯한 한국 남해안에서의 C. polykrikoides 적조 발생에 양쯔강 하천수가 기여하고 있음을 시사한다. We investigated marine environmental characteristics of the southern coastal waters of Korea including Eastern China Sea in the summer when Cochlodinium polykrikoides(hereafter C. polykrikoides) frequently occurs, using the data of NFRDI for the past 20years. Surface temperatures in Goheung coastal waters, where is known to be the first birthplace of C. polykrikoides blooms, appeared to be 19.527. 3℃ (mean 24.6℃), and kept almost constant. However, surface salinities were 27.01-33.83(mean 31.11), tending to rise annually. On the contrary, surface temperatures in the station 317-22(31.5°N, 124°E), where is the nearest point from the Yangtze River mouth, were higher by 1.3-3.01℃ than in Goheung while their surface salinities were 31.11, similarly to Goheung. In addition, horizontal distributions of the density(σt)) on the surface layer represented the possibility of the existence of a thermohaline front between the Korean Southern Coastal Waters and the Chinese Continental Coastal Waters. NOAA and NGSST satellite images also appeared that Yangtze River affects Jeju and Korean southern coasts. It suggests that the freshwater of Yangtze River may contribute to the occurrence of C. polykrikoides blooms in the Korean southern coastal waters in the summer.

봄철 제주도 서부해역의 수괴 분포와 수온역전 특징

강소영,문재홍 한국해양과학기술원 2022 Ocean and Polar Research Vol.44 No.3

Using the results of CTD casts made in Spring from 2017 to 2021, in this study we investigated the water mass distribution and occurrence of temperature inversion in the western seas of Jeju Island in spring. The distribution of water masses was characterized by cold and fresh water in the northwest and warm and saline water in the southeast, forming a strong thermohaline front running in the southwest-to-northeast direction. Strong temperature inversion mainly occurred in the frontal boundary when the cold water intrudes beneath the warm water at depths of 30–50 m. Analysis of the mixing ratio demonstrated that Jeju Warm Water is dominantly distributed in the western seas of Jeju Island, but its ratio can be modified depending on the southward extension of Yellow Sea Cold Water (YSCW). Results of in situ measurement showed that in 2020, the YSCW largely expanded to the western seas of Jeju Island, occupying approximately 40 % of the mixing ratio. Due to the expansion of YSCW, a strong thermohaline front was formed in the study area, thereby causing thick and strong temperature inversion. On the other hand, in 2018 the mixing ratio of YSCW was minimum (~18%) during the study period of 2017–2021, and thus a relatively weak frontal boundary was formed, without the occurrence of temperature inversion. The observational results also suggest that the interannual changes of water mass distribution and the associated temperature inversion in the western seas of Jeju Island are closely related with wind-driven Yellow Sea circulation in spring, which is the summer monsoon transition period.