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ORIGINAL RESEARCH article

Front. Mar. Sci.
Sec. Physical Oceanography
Volume 11 - 2024 | doi: 10.3389/fmars.2024.1425813

Summer marine heatwaves in the tropical Indian Ocean associated with an unseasonable positive Indian Ocean Dipole event 2012

Provisionally accepted
Zhiyuan LI Zhiyuan LI 1Gangfeng Wu Gangfeng Wu 1Chang Xu Chang Xu 1XIAO-HUA ZHU XIAO-HUA ZHU 2*Yu Long Yu Long 2
  • 1 Zhejiang Tongji Vocational College of Science and Technology, Hangzhou, Zhejiang Province, China
  • 2 State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, Hangzhou, Jiangsu Province, China

The final, formatted version of the article will be published soon.

    Marine heatwaves (MHWs) are anomalously warm events that profoundly affect climate change and local ecosystem. During the summer of 2012 (June-September), intense MHWs occurred in the tropical Indian Ocean (TIO) concurrently with an unseasonable positive Indian Ocean Dipole (pIOD) event. The MHW metrics (duration, frequency, cumulative intensity and maximum intensity) were characterized by northwestward-slanted patterns from west Australia to the Somalia coast. The analysis confirmed that these MHWs were closely associated with the unseasonable pIOD 2012. The weakening of Western North Pacific Subtropical High and strengthening of Australian High in spring induced an interhemispheric pressure gradient that drove two anticyclonic circulation patterns over the eastern TIO. The first anticyclonic circulation featured cross-equatorial wind anomalies from south of Java to the South China Sea/Philippine Sea, which led to strong upwelling off Sumatra-Java during the subsequent summer. The second anticyclonic circulation excited downwelling Rossby waves that propagated from the southeastern TIO to the western TIO. Thus, downwelling in the western pole and upwelling in the eastern pole led to a strong pIOD event peaking in summer, namely, the unseasonable pIOD 2012. These downwelling Rossby waves deepened the thermocline by more than 60 m and caused anomalous surface warming, thereby contributing to the occurrences of MHWs. With the development and peak of the unseasonable pIOD 2012, anomalous atmospheric circulation transported moisture from the TIO to the subtropical Western North Pacific (WNP), favoring a strong cyclonic anomaly that profoundly affected the summer monsoon rainfall over the subtropical WNP. This study provides some perspectives on the role of pIOD events in summer climate over the Indo-Northwest Pacific region.

    Keywords: Marine heatwave, Tropical Indian Ocean, Indian Ocean Dipole, interhemispheric pressure gradient, Downwelling rossby waves, subtropical Western North Pacific

    Received: 30 Apr 2024; Accepted: 15 Jul 2024.

    Copyright: © 2024 LI, Wu, Xu, ZHU and Long. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: XIAO-HUA ZHU, State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou, Hangzhou, Jiangsu Province, China

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