Marine heatwaves (MHWs) are extreme sea surface temperature (SST) events in all ocean basins, with far-reaching impacts on marine ecosystems and socio-economy. The leading patterns, trend, and interannual variability of summer MHWs in the tropical Indian Ocean (TIO) are investigated in this study. The first empirical orthogonal function (EOF) mode of frequency of MHWs exhibits a monopole pattern over the entire basin. This mode is highly associated with the concurrent Indian Ocean Basin warming, indicating a remarkable trend over the past four decades. The linear trend in MHW properties largely relates to increased summer Indian Ocean mean SST. The second EOF mode exhibits a zonal dipole with the MHW numbers increasing in the west and decreasing in the east. On the interannual timescale, the first two EOF modes are remotely affected by antecedent and concurrent El Niño events, respectively. The ocean mixed layer budget is utilized for examining the formation of different summer MHW patterns. During the preceding spring, the surface heat flux is important for the development of MHWs, while the ocean advections play a secondary role in the South Indian Ocean for the MHW monopole. Once the SST anomaly rises in summer, the ocean advections play a dominant role in maintaining the SST. Last, we assess the prediction skill of summer TIO MHWs by performing a bilinear seasonal statistical prediction model. Our results suggest the frequency of summer MHWs in the TIO could be predicted one season in advance. This study has great implications for understanding and predicting ocean extreme events in the TIO.

中文翻译：

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热带印度洋夏季海洋热浪的趋势和年际变化：模式、混合层热收支和季节预测


海洋热浪（MHW）是所有海洋盆地的极端海面温度（SST）事件，对海洋生态系统和社会经济产生深远影响。本研究调查了热带印度洋 (TIO) 夏季 MHW 的主要模式、趋势和年际变化。 MHW 频率的第一经验正交函数 (EOF) 模式在整个盆地表现出单极模式。这种模式与同时发生的印度洋盆地变暖密切相关，表明过去四十年来的显着趋势。 MHW 特性的线性趋势很大程度上与夏季印度洋平均海温的增加有关。第二个 EOF 模式呈现纬向偶极子，MHW 数在西部增加，在东部减少。在年际时间尺度上，前两种 EOF 模式分别受到先行厄尔尼诺事件和同时发生的厄尔尼诺事件的远程影响。海洋混合层预算用于研究不同夏季 MHW 模式的形成。在前一个春季，地表热通量对于 MHW 的发展非常重要，而南印度洋的海洋平流对于 MHW 单极子的作用起着次要作用。一旦夏季海温异常上升，海洋平流对维持海温起主导作用。最后，我们通过执行双线性季节性统计预测模型来评估夏季 TIO MHW 的预测技能。我们的结果表明，TIO 中夏季 MHW 的频率可以提前一季预测。这项研究对于理解和预测 TIO 海洋极端事件具有重要意义。