Abstract

Marine heatwaves (MHWs) are prolonged discrete events of anomalously warm seawater observed around the world. The occurrence of MHWs in the Japan/East Sea (JES), a middle latitude marginal sea with abundant aquatic resources, has severe impacts on marine ecosystems and human society. We used satellite remote sensing products spanning 1982–2020 to investigate the mean states and variations of JES MHWs. The results show that the JES MHWs occurred twice per year. More than 40% of the MHWs were shorter than the mean duration of 12.6 days and weaker than the mean intensity of 2.4 °C. Frequent MHWs were observed in August, while high mean intensities were observed in winter and spring in the western JES. In recent years, the area’s averaged yearly sum of MHW intensity in the JES has increased dramatically, with a positive trend of 29.62 °C days per decade—over twice the average global trend (12.37 °C days per decade), which is further confirmed by its first empirical orthogonal function mode. The strengthening trend in MHWs may be explained by oceanic dynamics rather than atmospheric forcing, and may result in increased surface latent heat flux from the ocean to the atmosphere.

Highlights

  • The MHWIMm varied from 0.01 °C to more than 5 °C in winter, wi values in the western Japan/East Sea (JES) and low values in the Tartar Strait and southeastern spring, the inhomogeneity of the spatial distribution decreased, the ma MHWIMm decreased to 4 °C, and the minimum MHWIMm increased to 1.7 °

  • The results show that the Pacific Decadal Oscillation (PDO), Arctic Oscillation (AO), and the El Niño–Southern Oscillation (ENSO) have no significant correlation with the significant increasing trend in the MHWIy [14]

  • High MHWTy and high sea surface temperature (SST) anomalies were both observed in the western JES at approximately 40◦ N. Both the spatial and temporal distributions of Marine heatwaves (MHWs) indices were subject to strong seasonal variability

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Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. MHWs have been observed around the world from open oceans to marginal seas and coastal regions, including the Pacific Ocean [7,8], Atlantic Ocean [9,10], Indian Ocean [11,12], Mediterranean Sea [2,3,13], Bering Sea [14], China Seas [15,16,17,18], Tasman Sea [19,20,21], the west coast of the United States [22], and the southwestern Atlantic shelf [23] These events have had severe impacts on marine ecosystems and human society, such as increasing fish mortality and bleaching coral [4,24,25,26,27].

Methods
10 February
Detection of Marine
Marine Heatwave Indices
Ekman Pumping
Seasonal
Interannual Variability and Long-Term Trends
Factors Associated with Long-Term Trends in Marine Heatwaves
Discussion and Conclusions
Findings
17. Mean trends global of marine heatwave indices fromindices
Summary
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