While the Atlantic Ocean is ventilated by high-latitude deep water formation and exhibits a pole-to-pole overturning circulation, the Pacific Ocean does not. This asymmetric global overturning pattern has persisted for the past 2–3 million years, with evidence for different ventilation modes in the deeper past. In the current climate, the Atlantic-Pacific asymmetry occurs because the Atlantic is more saline, enabling deep convection. To what extent the salinity contrast between the two basins is dominated by atmospheric processes (larger net evaporation over the Atlantic) or oceanic processes (salinity transport into the Atlantic) remains an outstanding question. Numerical simulations have provided support for both mechanisms; observations of the present climate support a strong role for atmospheric processes as well as some modulation by oceanic processes. A major avenue for future work is the quantification of the various processes at play to identify which mechanisms are primary in different climate states.

中文翻译：

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深水地层中的大西洋-太平洋不对称性

虽然大西洋通过高纬度深水地层通风并呈现出极到极的翻转环流，但太平洋却没有。这种不对称的全球翻转模式在过去的 2-3 百万年中一直存在，有证据表明在更深的过去存在不同的通风模式。在目前的气候下，大西洋-太平洋不对称发生是因为大西洋的盐度更高，可以进行深层对流。两个盆地之间的盐度对比在多大程度上由大气过程（大西洋上空较大的净蒸发）或海洋过程（盐分输送到大西洋）主导仍然是一个悬而未决的问题。数值模拟为这两种机制提供了支持；对当前气候的观测支持大气过程的重要作用以及海洋过程的一些调节作用。未来工作的一个主要途径是量化各种起作用的过程，以确定哪些机制在不同的气候状态下是主要的。