The Global Meridional Overturning Circulation (GMOC) is important for redistributing heat, and thus determining global climate, but what determines its strength over Earth’s history remains unclear. Based on two sets of climate simulations for the Paleozoic characterized by a stable GMOC direction, our research reveals that GMOC strength primarily depends on continental configuration while climate variations have a minor impact. In the mid-to-high-latitudes, the volume of continents largely dictates the speed of westerly winds, which in turn controls upwelling and the strength of the GMOC. At low latitudes, open seaways also play an important role in the strength of the GMOC. An open seaway in one hemisphere allows stronger westward ocean currents which support higher sea surface heights (SSH) in this hemisphere than that in the other. The meridional SSH gradient drives a stronger cross-equatorial flow in the upper ocean, resulting in a stronger GMOC. This latter finding enriches the current theory for GMOC.
全球经向翻转环流 (GMOC) 对于重新分配热量并因此决定全球气候非常重要，但是什么决定了它在地球历史上的强度仍不清楚。基于两组以稳定的 GMOC 方向为特征的古生代气候模拟，我们的研究表明，GMOC 强度主要取决于大陆结构，而气候变化的影响较小。在中高纬度地区，大陆的体积在很大程度上决定了西风的速度，而西风的速度又控制着上升流和 GMOC 的强度。在低纬度地区，开放的海道也在 GMOC 的强度中发挥着重要作用。一个半球的开放海道允许更强的西向洋流，从而支持该半球比另一个半球更高的海面高度 (SSH)。经向 SSH 梯度驱动上层海洋中更强的跨赤道流，从而导致更强的 GMOC。后一项发现丰富了目前关于 GMOC 的理论。