The 2016 record-breaking marine heatwave in the Yellow Sea and associated atmospheric circulation anomalies

Abstract

Marine heatwaves (MHWs) are becoming more frequent and intense in many regions around the world. However, the MHWs over China's marginal seas and associated physical drivers are largely unknown. During August 2016, the Yellow Sea experienced the most intense MHW on record since 1982. Here, we used a set of high-resolution satellite data and reanalysis products to examine the characteristics of the MHW in August 2016 and analyze the potential influencing factors from atmospheric perspective. MHW was directly caused by great-than-normal solar radiation and much weaker wind speeds which reduced upper oceanic mixing and caused substantial warming of the stratified surface layer. These anomalies were associated with an unusually fractured western Pacific subtropical high (WPSH) and the distinctly more active transmission of Madden-Julian Oscillation (MJO) eastward to the western Pacific in August 2016. The MJO triggered more frequent tropical cyclones, splitting the WPSH into two parts. The western segment of the WPSH combined with the continental high to form an abnormally positive geopotential height at the west of 120°E, causing strong subsiding flows at its east and extremely high solar radiation. An unambiguous cyclonic circulation anomaly in the lower troposphere, encompassing much of the northwestern Pacific, reduced the surface wind speed in the Yellow Sea. Therefore, MJO was critical to driving the extreme MHW in August 2016 in the Yellow Sea.