Effects of Heat and Momentum on the Sea Level in the Yellow and East Seas from 1993 to 2021

Abstract

The largest and smallest sea level differences between the Yellow Sea (YS) and East Sea (ES) were observed in September and December, respectively, in the 29-year mean (1993-2021). The sea level changes (SLCs) of the absolute dynamic topography (ADT) in the 29-year mean were 1.93 (YS) and 2.49 (ES) cm in September, and –4.88 (YS) and –3.65 (ES) cm in December. Using the ERA5 reanalysis data, the SLCs due to the atmospheric heat were –0.19 (YS) and –0.34 cm (ES) in September, and –2.05 (YS) and –3.24 cm (ES) in December. Ignoring the atmospheric and land effects of precipitation, evaporation, and runoff, oceanic effects could have contributed to the remaining SLC each month such as 2.12 (YS, 110 % ( 2.12 ÷ 1.93 × 100) of SLC of ADT) and 2.83 cm (ES, 114 % of SLC of ADT) in September and –2.83 (YS, 58 % of SLC of ADT) and –0.41 cm (ES, 11 % of SLC of ADT) in December. Our results showed that the oceanic effect significantly increased the sea level in both the YS and ES in September, whereas the atmospheric heat effect significantly decreased it in the ES in December, as the contribution of the oceanic effect was only –0.41 cm (11 % of SLC of ADT) in December. However, the accuracy of the reanalysis data was insufficient for a quantitative estimation of the ocean heat and mass transport divergence, limiting our interpretation. We have examined the correlation between mean sea level (MSL) and wind stress to analyze the oceanic effects contributing to the SLC. We found that Ekman transport may be one of the controlling factors contributing to the SLC in September and December. Our results require further quantitative analysis based on observations to investigate the oceanic and atmospheric effects on SLC in the study regions.