Understanding the ocean temperature change in global warming: the tropical Pacific

The response mechanisms of the tropical Pacific Ocean temperature to increased atmospheric CO₂ are investigated in a coupled climate model. Ensemble simulations are performed under both the transient and stable CO₂ forcing. It is found that the dominant mechanism for temperature change differs in different stages of global warming. During the transient stage, the surface heat flux is a major driving factor for the tropical surface warming. During the equilibrium stage, the dominant mechanism to maintain the surface warming is the meridional advection. The heat flux forcing becomes a damping factor instead, particularly for the western tropical Pacific. Different from the surface warming, the subsurface warming results from the oceanic mixings during the entire period of global warming, whereas the advection terms generally play a cooling role, consistent with the slowdown of the shallow meridional overturning circulation. This paper emphasizes the deterministic role of the dynamic adjustment of the ocean circulation in the long-term change of ocean climate.