Abstract The complexity of the tropical climate system demands the development of a hierarchy of models to ensure our understanding of its response to anthropogenic forcing. The response of the tropical Pacific Ocean to radiative forcing has been studied previously with a box model. The model has provided insights into the tropical Pacific climate change that are otherwise not easily attainable. But that model only encompasses the tropical Pacific region. Recent studies have also shown that the Indian Ocean (IO) may be important in the response of the Pacific Walker circulation to radiative forcing, raising the need to expand the model to take into account the role of IO. This study presents the results concerning the tropical Pacific response to radiative forcing from an expanded-box model that includes the tropical IO, which influences the tropical Pacific through an inter-basin SST gradient. The three-box model predicts an enhanced zonal SST gradient in tropical Pacific in response to the increased radiative forcing, similar to the previous two-box model. It is further noted that in the three-box model, a warmer IO relative to the Pacific enhances Pacific easterlies and subsequently strengthens the equatorial ocean circulation. Because of this ocean dynamical cooling, the warming response in the Pacific is effectively reduced in the three-box model that includes the role of IO compared with that in the two-box model. The role of the IO warming trend in enhancing the Pacific trade winds is confirmed using an atmospheric general circulation model experiment. These results may help to fully explain the relatively small observed warming trend in the tropical Pacific compared to that in the tropical IO evident in 20th century SST reconstructions.

中文翻译：

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印度洋在确定理想模型中热带太平洋海温对辐射强迫的响应中的作用

摘要 热带气候系统的复杂性要求开发模型的层次结构，以确保我们了解其对人为强迫的响应。热带太平洋对辐射强迫的响应以前曾用箱形模型进行过研究。该模型提供了对热带太平洋气候变化的深入了解，否则很难实现。但该模型仅涵盖热带太平洋地区。最近的研究还表明，印度洋 (IO) 在太平洋沃克环流对辐射强迫的响应中可能很重要，因此需要扩展模型以考虑 IO 的作用。本研究展示了热带太平洋对辐射强迫的响应结果来自一个扩展箱模型，该模型包括热带 IO，它通过跨盆地海温梯度影响热带太平洋。三盒模型预测热带太平洋的纬向海温梯度随着辐射强迫的增加而增强，类似于之前的两盒模型。进一步注意到，在三箱模型中，相对于太平洋更暖的 IO 增强了太平洋东风，随后加强了赤道海洋环流。由于这种海洋动力冷却，与两箱模型相比，包含 IO 作用的三箱模型有效降低了太平洋的变暖响应。使用大气环流模型实验证实了 IO 变暖趋势在增强太平洋信风方面的作用。