Closure of the Bering Strait to prevent an AMOC tipping

The present-day Atlantic Meridional Overturning Circulation (AMOC) is considered to be a prominent tipping element and its collapse would have grave consequences on the global climate. Its dynamics are partly determined by the Bering Strait Throughflow where fresh Antarctic Intermediate Water from the Pacific Basin enters the Arctic Ocean through the Bering Strait and eventually joins the lower branch of the AMOC through deep-water formation in the North Atlantic. The Throughflow's net effect is a freshening of the North Atlantic. Closure of the Bering Strait produces therefore a strengthening of the AMOC. Various studies have indicated that the AMOC is weakening and may even collapse before the end of this century. As the Bering Strait is only 80 km wide and on average 50 m deep an enclosure dam is technically feasible as a measure to strengthen the AMOC and prevent its tipping. In this work we use a hierarchy of climate models including CESM1 to study the effect of a Bering Strait closure on the AMOC under various climate and freshwater forcings. It shows that for low freshwater forcings to the North Atlantic a closure can mitigate the weakening of the AMOC and even prevent an AMOC tipping due to climate forcing. However, for larger freshwater forcings a Bering Strait closure destabilizes the AMOC and would make a tipping more likely as now the additional freshwater can no longer directly be exported out off the North Atlantic to the Pacific via the Bering Strait. Additionally, a small conceptual model is employed in order to illuminate these results further.