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Article

Estimation of Mean Surface Current and Current Variability in the East Sea using Surface Drifter Data from 1991 to 2017

1991년부터 2017년까지 표층 뜰개 자료를 이용하여 계산한 동해의 평균 표층 해류와 해류 변동성

JU-EUN PARK1
,
SOO-YUN KIM1
,
BYOUNG-JU CHOI1
,
DO-SEONG BYUN2
박 주은1
,
김 수윤1
,
최 병주1
,
변 도성2
1Department of Oceanography, Chonnam National University
2Ocean Research Division, Korea Hydrographic and Oceanographic Agency
1전남대학교 해양학과
2국립해양조사원 해양과학조사연구실
* Corresponding Author
31 May 2019. pp. 208-225
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Abstract

동해의 평균 표층 순환과 표층 해류의 변동성을 이해하기 위하여 1991년부터 2017년까지 동해를 지나간 표층 뜰개들의 궤적을 분석하였다. 표층 뜰개 자료를 분석하여 동해 표층 해류들을 그 주경로 별로 분류하고, 이들 해류의 변동을 조사하였다. 동한난류는 한국 동해안을 따라 북쪽으로 흐르며 36∼38°N에서 이안한 후 동해 중앙(131∼137°E)에서 동쪽으로 흐른다. 이때 해류 경로의 평균 위도는 36∼40°N의 범위를 가지며, 남북으로 큰 진폭을 갖고 사행한다. 표층 뜰개 경로의 평균 위도가 37.5°N 이남(이북)일 때 사행진폭이 상대적으로 크며(작으며) 진폭은 약 100 (50) km이다. 동해 중앙에서 표층 뜰개들은 37.5∼38.5°N를 따라 동쪽으로 흐르는 경로를 가장 빈번하게 지나간다. 동해 북부 블라디보스토크 연안에 투하된 표층 뜰개들은 연안을 따라 남서쪽으로 이동하다가 일본분지 서쪽에서 반시계방향 순환을 따라 남동쪽으로 이동한 후 39~40°N에서 동쪽으로 사행하여 이동한다. 다음으로 동해를 0.25° 간격으로 격자를 나누어 각 격자를 통과하는 표층 뜰개들의 이동 속도 벡터 자료로 동해 평균 표층 해류 벡터장과 속력장을 구하였다. 그리고 0.5° 격자 간격으로 해류장의 분산타원을 계산하였다. 울릉분지 서쪽에서는 동한난류의 경로가 매년 변화하고, 야마토분지에서는 해류의 사행과 소용돌이가 많아 해류의 변동성(분산)이 크다. 표층 뜰개의 주 이동 경로, 평균 해류 벡터장, 분산을 모두 반영하여 표층 뜰개 자료에 근거한 동해 표층 해류 모식도를 제시하였다. 이 연구는 그동안 인공위성 고도계 자료를 이용하여 구한 표층 지형류와 해양수치모델로 모의한 해류를 중심으로 연구해 왔던 동해 표층 순환을 라그랑지 관측 자료를 통해 정리했다는 데 의의가 있다.

To understand the mean surface circulation and surface currents in the East Sea, trajectories of surface drifters passed through the East Sea from 1991 to 2017 were analyzed. By analyzing the surface drifter trajectory data, the main paths of surface ocean currents were grouped and the variation in each main current path was investigated. The East Korea Warm Current (EKWC) heading northward separates from the coast at 36∼38°N and flows to the northeast until 131°E. In the middle (from 131°E to 137°E) of the East Sea, the average latitude of the currents flowing eastward ranges from 36 to 40°N and the currents meander with large amplitude. When the average latitude of the surface drifter paths was in the north (south) of 37.5°N, the meandering amplitude was about 50 (100) km. The most frequent route of surface drifters in the middle of the East Sea was the path along 37.5‒38.5°N. The surface drifters, which were deployed off the coast of Vladivostok in the north of the East Sea, moved to the southwest along the coast and were separated from the coast to flow southeastward along the cyclonic circulation around the Japan Basin. And, then, the drifters moved to the east along 39-40°N. The mean surface current vector and mean speed were calculated in each lattice with 0.25° grid spacing using the velocity data of surface drifters which passed through each lattice. The current variance ellipses were calculated with 0.5° grid spacing. Because the path of the EKWC changes every year in the western part of the Ulleung Basin and the current paths in the Yamato Basin keep changing with many eddies, the current variance ellipses are relatively large in these region. We present a schematic map of the East Sea surface current based on the surface drifter data. The significance of this study is that the surface ocean circulation of the East Sea, which has been mainly studied by numerical model simulations and the sea surface height data obtained from satellite altimeters, was analyzed based on in-situ Lagrangian observational current data.

Keywords
Surface drifter
Surface current
East Sea
East Korea Warm Current
Mean current
Current variance ellipse

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Information
  • Publisher :The Korean Society of Oceanography
  • Publisher(Ko) :한국해양학회
  • Journal Title :The Sea Journal of the Korean Society of Oceanography
  • Journal Title(Ko) :한국해양학회지 바다
  • Volume : 24
  • No :2
  • Pages :208-225
  • Received Date : 2018-12-09
  • Revised Date : 2019-04-15
  • Accepted Date : 2019-05-27
  • DOI :https://doi.org/10.7850/jkso.2019.24.2.208
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