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Long-term Trend Analysis of Cold Waters along the Eastern Coast of South Korea

동해 냉수대 발생역의 장기 변동 분석

  • Kim, Ju-Yeon (Ocean Climate of Ecology Research Division, National Institute and Fisheries Science) ;
  • Han, In-Seong (Ocean Climate of Ecology Research Division, National Institute and Fisheries Science) ;
  • Ahn, Ji-Suk (Ocean Climate of Ecology Research Division, National Institute and Fisheries Science) ;
  • Park, Myung-Hee (Ocean Climate of Ecology Research Division, National Institute and Fisheries Science)
  • 김주연 (국립수산과학원 기후변화연구과) ;
  • 한인성 (국립수산과학원 기후변화연구과) ;
  • 안지숙 (국립수산과학원 기후변화연구과) ;
  • 박명희 (국립수산과학원 기후변화연구과)
  • Received : 2019.06.25
  • Accepted : 2019.08.28
  • Published : 2019.08.31

Abstract

A long-term trend analysis of cold water masses along eastern coast of South Korea was performed during summer, based on wind speed, wind direction, and sea surface temperature (SST) data. Wind data collected over a 22-year period (1997-2011) were compared with another set of data collected over the successive 7-year (2012-2018), highlighting a general decrease in the frequency and speed of south winds. However, both the frequency and speed of these winds have been higher in June between 2012-2018, rather than between 1997-2011. The cold water season between July and August was faster during the 7-year period; moreover, the SSTs registered around Gangneung (EN) rose by $0.5^{\circ}C- 1.8^{\circ}C$, while those around Yeongdeok (EC) and Gijang (ES) increased by only $0.1^{\circ}C-0.3^{\circ}C$. The number of cold water days during the 7-year period, compared to those recorded during previous years (1990-2011, satellite SST data by NOAA/AVHRR), decreased in the proximity of Yeongdeok and Gijang, but increased in the proximity of Kangneung. Additionally, the number of cold water days around Kangneung, Yeongdeok, and Gijang increased in June highlighting a geographical and temporal change in the occurrence of cold waters. These observation can be explained by variations in the pressure distribution that should have weakened the East Asian monsoon, affecting the direction and speed of winds that regulate the flow of cold waters.

본 연구에서는 여름철 동해안 냉수대 해역의 바람의 세기 및 방향과 수온의 장기 변동성을 살펴보았다. 바람분석 결과, 과거 22년(1997년~2011년)과 최근 7년(2012년~2018년)을 비교해 보면 여름철 동안 과거에 비해 최근에 남풍계열 바람의 빈도가 줄었고, 풍속도 약해지는 경향을 보였다. 그러나 6월의 바람은 남풍계열 바람의 빈도와 풍속이 과거에 비해 증가하는 경향을 보였다. 이는 7월과 8월에 주로 나타난 냉수대 시기가 빨라졌다고 분석되었다. 최근 7년 사이 강릉(EN) 해역에서 $0.5^{\circ}C{\sim}1.8^{\circ}C$의 수온 상승을 보였으며, 영덕(EC)과 기장(ES)은 $0.1^{\circ}C{\sim}0.3^{\circ}C$의 수온 상승을 보였다. 평년(1990년~2011년, NOAA/AVHRR 위성수온자료) 대비 최근 7년의 냉수대 출현일은 영덕과 기장에서 줄어드는 경향을 보였고, 강릉은 상대적으로 냉수대 출현일이 증가하는 추세를 보였다. 또한 강릉, 영덕, 기장 해역에서 6월에 냉수대 출현이 증가하는 경향을 보여 냉수대 발생 해역과 시기에 변화가 발생 된 것으로 분석된다. 이러한 결과는 우리나라 주변의 여름철 동아시아 몬순의 약화가 냉수대의 발생원인인 풍향과 풍속에 영향을 미쳤기 때문으로 판단된다.

Keywords

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