The Indonesian sea is the only low-latitude pathway connecting two tropical oceans, which plays an important role in the coupled ocean-atmosphere mode in the Indo-Pacific sector. A small change in the sea surface temperature (SST) in the Indonesian sea has a significant influence on the precipitation and air-sea heat flux. During the past 33 years, the SST in the Indonesian sea has indicated a warming trend on the average of 0.19 ± 0.04 decade⁻¹, which is larger than global SST warming trend. Moreover, the warming trend indicates seasonal variations, in which maximum trend occurred during boreal summer season. Investigation on the potential driver for this warming trend, namely, the net surface heat flux, resulted in an opposite trend (cooling trend), while the Ekman pumping and the wind mixing only play a minor role on the SST warming. Here, we proposed the upper layer process associated with an increasing trend in precipitation and decreasing trend in mixed layer depth (MLD) for the SST warming within the Indonesian seas. Shoaling of MLD gives a favorable condition for the surface heat flux to warm the surface ocean. However, shoaling of MLD could not solely explain the total SST warming within the Indonesian seas. The seasonal dependence in the warming trend, highest during boreal summer, was significantly related to the Indo-Pacific climate modes, namely the negative Indian Ocean Dipole (IOD) and La Niña events. Higher warming trend observed in the south of Makassar Strait and in the eastern Indonesian seas, in the vicinity of the Maluku Sea and the northeastern part of the Banda Sea, was significantly associated with the La Niña event. Meanwhile, strong warming trend observed in the Karimata Strait and Java Sea, and in the Flores Sea south of Sulawesi Island seems to be enhanced by the negative IOD event. Our rough quantitative estimate of the possible mechanism leading to the SST warming suggests that other mechanism might be at work in warming the SST within the Indonesian seas. Horizontal heat advection associated with an increasing trend of the heat transport from the Pacific into the Indian Ocean by the Indonesian Throughflow (ITF) might play a role in causing the warming trend within the Indonesian seas. However, to what extend this heat advection could modulate the SST warming is still unresolved in the present study. Further study based on realistic model output as well as long-term observational records is necessary to describe the dynamics underlying the warming trend within the Indonesian seas.

中文翻译：

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是什么决定了印尼海域的变暖趋势？

印度尼西亚海是连接两个热带海洋的唯一低纬度路径，它在印度太平洋地区的海洋-大气耦合模式中发挥着重要作用。印尼海中海表温度（SST）的微小变化对降水量和海气热通量有重大影响。在过去的33年中，印度尼西亚海域的SST呈变暖趋势，平均为0.19±0.04十年^-1，这大于全球SST变暖趋势。此外，变暖趋势表明季节变化，其中最大趋势发生在夏季北方。对这种变暖趋势的潜在驱动因素（即表面净热通量）的研究得出了相反的趋势（冷却趋势），而埃克曼泵送和风的混合在SST变暖中仅起很小的作用。在这里，我们提出了印度尼西亚海SST增暖的降水增加趋势和混合层深度（MLD）减少趋势相关的上层过程。MLD的暗化为表面热通量加热海洋表面提供了有利条件。但是，MLD的浅滩并不能完全解释印度尼西亚海域SST的总体变暖。变暖趋势的季节依赖性，北方夏季最高，与印度-太平洋气候模式显着相关，即负印度洋偶极子（IOD）和拉尼娜事件。在望加锡海峡南部和印度尼西亚东部海域，在马鲁古海附近和班达海东北部，观察到较高的变暖趋势与拉尼娜事件显着相关。同时，负IOD事件似乎增强了在Karimata海峡和爪哇海以及苏拉威西岛以南的弗洛雷斯海的强烈变暖趋势。我们对导致SST变暖的可能机制的粗略定量估计表明，其他机制可能正在使印度尼西亚海域的SST变暖。与印尼通流（ITF）从太平洋向印度洋的热传输增加趋势相关的水平热对流可能在引起印尼海域变暖趋势中起作用。然而，在目前的研究中仍未解决这种热对流能扩展SST变暖的程度。为了描述印尼海域变暖趋势的动态，有必要根据实际模型输出以及长期的观测记录进行进一步研究。