Effect of a Bering Strait Closure on AMOC Resilience in a Climate Box Model

Abstract. Recent simulations in an EMIC (CLIMBER-X) have shown that a constructed closure of the Bering Strait can shift the safe carbon budget of the Atlantic Meridional Overturning Circulation (AMOC). In this study we extend a conceptual ocean box model by introducing an atmospheric temperature forcing and a freshwater transport induced by the Bering Strait Throughflow (BST). With this model we can replicate the results produced by CLIMBER-X, and test their sensitivity with respect to forcing and BST parameters. Bifurcation analyses show that a closure of the Bering Strait has a destabilizing effect on an AMOC perturbed by freshwater hosing, but can have a stabilizing effect on an AMOC forced by a polar amplification in atmospheric temperatures – provided the freshwater hosing is limited. A temperature-induced weakening of the AMOC sees a reversal of the BST, which then exports relatively saline waters out of the North Atlantic, and so a closure can have a stabilizing effect. The effectiveness of a closure to prevent a temperature-induced AMOC collapse is sensitively dependent on both the BST parameter values and the rate of the applied forcing. Moreover, the timing of the last preventive closure relies heavily on the forcing rate as well. These conceptual results are important for understanding the feasibility of a Bering Strait closure in order to prevent an AMOC collapse under climate change.