The impact of sound speed variability in the sea is the very important on acoustic propagation for the underwater acoustic systems. Understanding of the temporal and spatial variability of ocean sound speed in the sea around the Ieodo were obtained using oceanographic data (temperature, salinity). from the Korea Oceanographic Data Center, collected by season for 17 years. The vertical distributions of sound speed are mainly related to seasonal variations and various current such as Chinese coastal water, Yellow Sea Cold Water (YSCW), Kuroshio source water. The standard deviations show that great variations of sound speed exist in the upper layer and observation station between 16 and 18. In order to quantitatively explain the reason for sound speed variations, Empirical Orthogonal Function (EOF) analysis was performed on sound speed data at the Line 316 covering 68 cruises between 2002 and 2018. Three main modes of EOFs respectively revealed 55, 29, and 5% the total variance of sound speed. The first mode of the EOFs was associated with influence of surface heating. The second EOFs pattern shows that contributions of YSCW and surface heating. The first and second modes had seasonal and inter-annul variations.

Abstract
1. 서 론
2. 재료 및 방법
3. 결과 및 고찰
    3.1. 계절별 평균수온 수직분포
    3.2. 계절별 평균염분 수직분포
    3.3. 계절별 평균음속 수직분포
    3.4. 음속의 표준편차와 경험직교함수 분석
4. 결 론
REFERENCES

• 박경주(해군사관학교 해양학과) | Kyeongju Park (Department of Oceanography, ROK Naval Academy, Chinhae 51704, Korea) Corresponding author