| 30 Jan 2026
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.
This manuscript extends the five-box AMOC model framework of Wood et al. (2019) to study how an open versus closed Bering Strait affects AMOC stability. The authors (i) include an idealised Bering Strait Throughflow parameterisation linking BST transport (q_b) to AMOC strength (q_n) (ii) add a prognostic temperature framework (enabling temperature-forced weakening/tipping in addition to freshwater hosing). The extended box model is calibrated to a stable pre-industrial state of FAMOUS, and results are compared qualitatively with earlier CLIMBER‑X experiments.
I see value in this type of conceptual modelling: while a box model should not be interpreted quantitatively as a predictor of real-world thresholds, it can be useful for mechanism isolation and hypothesis generation, especially when it is tied back to behaviour seen in a more complex model.
My main concern is not the scientific motivation but the presentation: I found the narrative overly complex given the conceptual nature of the study. Several key conclusions are present, but the manuscript would benefit strongly from clearer “take-home messages” per section and from avoiding ambiguous phrasing that mixes open- and closed-strait configurations.
Major comments
1. Abstract clarity and configuration separation (OBS vs CBS): The abstract states that “closure … has a destabilizing effect” and shortly afterwards that a temperature-induced weakening “sees a reversal of the BST”. This can be read as internally inconsistent unless it is explicitly stated that BST reversal occurs only in the open Bering Strait configuration (OBS), whereas in the closed configuration (CBS) there is by definition no throughflow to reverse. I recommend adding one short clause in the abstract to make this explicit (“In the open-strait configuration the throughflow can reverse…”, or similar).
2. Section-level summaries and signposting: From Section 3 onwards, I suggest adding 1–2 sentences at the end (or start) of each subsection summarising: (i) what was tested, (ii) what the result is (direction of change), and (iii) why it happens physically (one mechanism). This will substantially improve readability without changing results.
3. Clarify the statement around (q_0=5.8) Sv and the tipping point (around line ~201): The text says: “This is because at (q_0 = 5.8) Sv the BST switches at the tipping point, since (q_n|{F_H^1}=5.8) Sv then as well.” Please clarify how the value (q_n|{F_H^1}=5.8) Sv is obtained..
4. Clarify the core “message” of the paper as a small set of regimes: The results depend on (a) the forcing type (freshwater hosing vs temperature forcing) and (c) BST parameters ((q_0), (\nu)). Consider adding a short schematic or a concise paragraph in the summary/discussion that states, in plain language, the regimes under which closure stabilises vs destabilises the AMOC in this framework.
I recommend the paper for publication after minor revision.