Variabilities of Temperature and Current in the East China Sea Related to the Variability of the Kuroshio in the Southern East China Sea

Kuroshio flowing on the shelf break of the East China Sea (ECS) has a major influence on the temperature and current fields in the ECS. We investigated the variabilities of temperature and current in the ECS related to the transport of theKuroshio in the southern ECS using HYCOM data. There is a tendency that temperature in the northeast of Taiwan is high when the Kuroshio transport is small, which implies large intrusion of warm water across the continental shelf since on-shelf intrusion is obvious when the Kuroshio transport is small. In the current fields, northeastward/southwestward anomalies through the Taiwan strait are shown when the Kuroshio transport is large/small, implying the Taiwan Warm Current transports more/less water into the ECS. It is also shown that the Cheju Warm Current, which rounds Cheju island clockwise and flows eastward through the Cheju strait, and current through the Korea strait are related to the Kuroshio transport.1

Variation of the Kuroshio axis in the East China Sea

Fluctuations of the Kuroshio axis in the East China Sea and their relations to variations of temperature and sea surface height are investigated using HYCOM data. Prominent fluctuations of the Kuroshio axis are shown in the east of Taiwan, northeast of Taiwan, and southwest of Kyushu. Local changes of temperature associated with the fluctuations of the Kuroshio axis at the three regions show dipole-like structures, cooling (warming) on the immediate onshore (offshore) side of Kuroshio axis when the Kuroshio axis is located offshore. The dipole-like structures are also shown in changes of sea surface height, but their centers are not located along the Kuroshio axis but on the offshore side of the Kuroshio axis.northeast of Taiwan, and southwest of Kyushu. Local changes of temperature associated with the fluctuations of the Kuroshio axis at the three regions show dipole-like structures, cooling (warming) on the immediate onshore (offshore) side of Kuroshio axis when the Kuroshio axis is located offshore. The dipole-like structures are also shown in changes of sea surface height, but their centers are not located along the Kuroshio axis but on the offshore side of the Kuroshio axis.1

東海 中層 海水 物性의 長期 變化

Thesis (doctoral)--서울대학교 대학원 :지구환경과학부,2002.Docto

Numerical Experiment of Environmental Change in the East China Sea under Climate Change

We simulated and compared present and future ocean circulation in the East China Sea using an East Asia Regional Ocean model. Mean climate states for 1990~1999 and 2030~2039 were used as surface conditions for simulations of present and future ocean circulation, which were derived from the simulations of three different global climate models, ECHAM5-MPI, GFDL-CM2.0 and MIROC3.2_hires, for the 20th century and those of 21st century as projected by the IPCC SRES A1B. East Asia Regional Ocean model simulated the detailed patterns of temperature, salinity and current fields under present and future climate conditions and their changes instead of the simple structures of global climate models. To some extent, there are consistent ocean circulation changes derived from the three pairs corresponding to the global climate model in so much as the temperature increases not only in winter but summer at both the surface and bottom and that temperature and salinity changes are prominent near the Chinese coast and in the Changjiang bank. However, the simulated circulations are different among each other depending on the prescribed atmospheric conditions not only under present climate but also with regard to future climate conditions. There is not a coincident tendency in ocean circulation changes between present and future simulations derived from the three pairs. This suggests that more simulations with different pairs are needed.33scopuskc

Simulation of Ocean Circulation in the East China Sea Under Future Climate Condition

North Pacific ocean climate model experiments have been conducted to examine a possible change of ocean environment under global warming in the East China Sea (ECS) which is not adequately resolved in global climate models due to a coarse spatial resolution. Global climate model simulations for the 20th century and for the future climate with IPCC A1B scenario were used as the prescribing conditions. Compared to the global climate models, regional ocean climate model predicted the detailed patterns of temperature and current fields under the future climate condition; instead of simple structure like an overall temperature rise as in global climate models, locally different rising/falling trend of temperature in the ECS. Future temperature and salinity changes are prominent in the Changjiang bank shallower than 70 m in the western region of the ECS, while those are relatively small in the eastern region where the Kuroshio-branched current flows northeastward.1

Long-term variability of SST adjacent to the Korean coast

한국 연안 수온의 장기 변동을 파악하기 위해 국립해양조사원과 국립수산과학원의 연안정지관측 수온을 분석하였다. 자료공백이 15일 이상 60일 이하인 경우는 전년도와 후년도의 같은 시기의 평균값으로, 15일 이하인 경우는 선형 내삽한 값으로 대체하였다. 스펙트럼 분석 결과 연변동주기 이외의 6개월 주기성분이 크게 나타났다. 연변동을 제거하기 위하여 2년 이하의 단주기성분을 제거한 후 수온의 장기 선형 증가 경향을 구한 결과, 한국연안의 대부분 관측점에서 통계적으로 유의한 증가 경향이 나타났다. 인접 관측점의 시계열에서도 증가율의 차이가 보이는 경우가 있고 두 기관의 자료가 차이가 나는 경우도 있으나 대부분 0.02℃/년 이상의 증가율을 보인다. 연변동 성분을 추출하기 위해 6개월-2년 band-pass filter를 한 후 각 해의 최저수온과 최고수온, 연변동폭의 변동성을 분석하였다. 수온의 장기증가경향을 보이는 시계열에 비해 통계적으로 유의한 선형변화추세를 보이는 시계열의 수는 적으나 최저수온은 증가하는 경향이, 최고 수온은 약간 감소하는 경향이 나타났다. 이런 최저수온과 최고수온의 변화경향에 따라 연변동폭은 결과적으로 감소하는 경향이 나타났다. 관측점에 따른 변화경향의 차이, 특히 다른 관측점에 비해 속초의 수온이 유난히 큰 변화경향을 보이는 원인을 파악하기 위해 더 세밀한 분석을 할 예정이다.2

Review on the climate change in the seas around the Korean Peninsula

한반도 주변해역에서 이루어진 기후변화연구에 대해 고찰하였다. 장기해표면수온에 대한 연구들에서 표면수온의 장기적 증가추세가 비교적 명확히 나타났으며, 연안검조자료 분석결과에서는 여러 지점에서 대체로 해수면의 증가경향이 나타났다.2

Variation of SST adjacent to the Korean coast

In this study, long-term variability in the coastal sea surface temperature (SST) in Korea was investigated to examine the earlier results in depth by analyzing the coastal SST time series extending to recent years. Spectral analysis shows not only dominant peak of annual period as expected but also evident peak of semi-annual period at most of the stations with 4-month period at some stations. It is shown that interannual variability has a common tendency at most of the stations with some differences between eastern and western coast. Long term increasing trend is remarkable at almost all the stations with the rate over 0.02°C/year. The increasing trend of minimum SST in winter is obvious at most stations and the increasing rate is larger at the stations in the eastern coast, but the linear trend of maximum SST in summer is less definite. Therefore, the decreasing tendency of annual amplitude is mainly due to the increasing tendency of SST in winter.1

A global ocean circulation modeling: comparison with observations

0.5도 전구 해양대순환 모형의 품위을 관측 자료와의 비교를 통해 검증하였다. 중, 저위도 의 수온은 약 200 미터 까지는 관측보다 낮게, 그 이심에서는 높게 모사되었다. 북태평양 해면수온은 쿠로시오의 극치우침과 동적도태평양의 과도하게 찬 해수로 인해 그 분포가 관측과 크게 차이가 났다. 모형이 관측 열속 (SOC)에 비해 대기로 열을 적게 보내고 적게 받아들였다.2

Temporal variation of the North Korean Cold Current in the East Sea Reanalysis

1993년부터 2002년까지 10년간의 동해 수온 및 염분 그리고 해류의 재분석 자료를 이용하여 북한한류의 시계열 특성을 분석하였다. 재분석 자료에서 북한한류는 늦은 겨울이나 봄철부터 남하하기 시작하면서 수송량이 증가하다가 3~5월경에 감소한 후 다시 증가하여 8~9월경에 최대인 0.8 Sv에 이르는 계절변동을 보였으며, 북한한류 수송량의 계절변동폭은 약 0.35 Sv이었다. 1996년과 1999년 8월에는 북한한류 수송량이 1.6 Sv 이상이었으나 2001년 8월에는 0.4 Sv 이하로 나타나는 등 10년 동안 북한한류 수송량의 경년변동폭은 1.2 Sv이었다. 해에 따른 북한한류 수송량의 연별 계절변동에서 북한한류 수송량은 1월부터 증가하기 시작하여 2월 또는 3월부터 감소한 후 다시 4월이나 5월에 증가하기 시작하여 8월이나 9월에 최대에 이른 후 감소하는 형태가 10년 중에서 가장 일반적인 계절변동으로 나타나 기후월평균 계절변동과 유사하였다.2