Interannual Variability of Winter Sea Levels Induced by Local Wind Stress in the Northeast Asian Marginal Seas: 1993–2017

Myeonghee Han,Hyoun-Woo Kang,Yang-Ki Cho,Sunghyun Nam,Eunil Lee,Kwang-Young Jeong

doi:10.3390/jmse8100774

Abstract

The interannual variability of winter sea levels averaged over the northeast Asian marginal seas, consisting of the Yellow Sea, East China Sea, and the East Sea (ES), was investigated. The spatial-mean sea level in winter observed using satellite altimetry shows significant interannual variations with a long-term rising trend of 3.88 mm y−1 during 1993–2017, with relatively high (Period H) and low (Period L) sea level anomalies. These anomalies correlate with the patterns of the East Asian winter monsoon at interannual timescales. The atmospheric pressure difference between the Sea of Okhotsk (SO) and ES around the Soya Strait is large during Period H. Ekman transport increases due to enhanced southeastward wind stress and results in a horizontal mass convergence that yields positive sea level anomalies during Period H. In contrast, the wind-induced transport is enhanced in the southern ES rather than in the southern SO resulting in horizontal mass divergence and negative anomalies in the spatial-mean winter sea level during Period L. Our results highlight the important roles of local wind forcing and Ekman dynamics in inducing interannual winter sea level variability in the region indicating the high predictive ability of atmospheric pressure anomalies around the Soya Strait.

Highlights

In addition to global sea level variability, mean sea level variability in a marginal sea, which directly affects surrounding countries and many lives, is controlled by diverse processes
Using the winter mean turbulent heat flux of ~300 W m−2 reported for the region [46], 13% higher and 5% lower cooling effects are estimated due to sea surface wind speeds (5.37 m s−1 compared to 4.82 m s−1 and 4.57 m s−1 compared to 4.82 m s−1, respectively), which are stronger during Period L and weaker during Period H compared to the mean for the total period
We presented the interannual variations of winter sea levels averaged over the northeast Asian marginal seas (NEAMS) for a 25-year period from 1993 to 2017, which were successfully explained by horizontal water convergence and divergence due to monsoonal wind-induced Ekman transport

Summary

Introduction

In addition to global sea level variability, mean sea level variability in a marginal sea, which directly affects surrounding countries and many lives, is controlled by diverse processes. Our understanding of the processes that control regional sea level variability is far from complete despite the increasing concern about rising global sea levels. This is the case for the northeast Asian marginal seas (NEAMS), which consist of the Yellow Sea (YS), East China Sea (ECS), and East Sea (ES or the Sea of Japan), excluding the Sea of Okhotsk (SO).

Data and Methods

Findings

Discussion

Conclusions