Surface Warming Slowdown With Continued Subsurface Warming in the East Sea (Japan Sea) Over Recent Decades (2000–2014)

Yubeen Jeong,Young-Heon Jo,Jae-Il Kwon,Sunghyun Nam,Umakanth Uppara

doi:10.3389/fmars.2022.825368

Abstract

The long-term surface warming trend in the East Sea (Japan Sea; ES hereafter) stalled from 2000 to 2014 (−0.05°C yr−1, surface warming slowdown), while the subsurface (100–300°m) warming trend continued (+0.03°C yr−1). To address the processes underlying these contrasting trends in surface and subsurface temperature change, the trends in sea-level anomaly, isopycnal depth, and wind pattern were analyzed using monthly mean ocean reanalysis system 4 (ORAS4) data. During this period, the strengthened northwesterly/northerly wind in the central part of ES is supposed to contribute to a negative (positive) wind stress curl to its west (east), corresponding to an anticyclonic (cyclonic) circulation in the west (east). Furthermore, the induced negative wind stress in the west appears to enhance the northward penetration of East Korean Warm Current (EKWC), the slowdown in its eastward meandering around 38° N from the Korea coast, resulting in warm water accumulation in the west with peak warm anomaly at relatively greater depth compared to peak cold anomaly in the east. Overall, these wind-driven changes in transport from west to east, wind stress curl induced horizontal divergence (convergence) and the associated upwelling (downwelling), causes surface warming to slow and subsurface warming to persist during 2000 to 2014.

Highlights

During the global warming hiatus period from 1998 to 2013 (IPCC, 2013, 2014; England et al, 2014), the surface warming trend decreased from 0.12◦C yr−1 to 0.05◦C yr−1; the heat content below the sea surface continued to increase, contrary to the pause in surface warming
Considering that the increasing trend of the global mean sea surface temperature anomaly (SSTA) changed from 0.12◦C yr−1 to 0.05◦C yr−1 (IPCC, 2014) during the period from 2000 to 2014, the trend changes in the ES is similar to that of the global trend
We conducted a trend analysis of sea surface and subsurface temperature anomalies, sea level anomaly (SLA), isopycnals, and wind stress curl, and our findings are summarized as follows: 1. From 2000 to 2014, a significant surface warming slowdown occurred in the ES compared to the previous warming period (1985–1999), which was defined as the SWS period

Summary

Introduction

During the global warming hiatus period from 1998 to 2013 (IPCC, 2013, 2014; England et al, 2014), the surface warming trend decreased from 0.12◦C yr−1 to 0.05◦C yr−1; the heat content below the sea surface continued to increase, contrary to the pause in surface warming. The ES is a semi-enclosed deep marginal sea connected to the Pacific through narrow and shallow straits, with the lowest deep-water temperature and highest deep-water dissolved oxygen in the Pacific It has high warming rates among all oceans worldwide and is significantly affected by global warming trend (Kim et al, 2001; Talley et al, 2006; Belkin, 2009; Gamo, 2011). The bottom water formation in ES has been enhanced since 2000, which indicates water formation and ventilation processes can provide significant climatic implication (Yoon et al, 2018)

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Conclusion