The Younger Dryas cooling was proximately produced by a major weakening or reorganization of the Atlantic Meridional Overturning Circulation.

Multiple independent paleoceanographic proxy lines; accepted by both camps. Diagnostically inert for the trigger question, which is the question.

The proximate mechanism of a weakened AMOC causing the Younger Dryas is well supported. Paleoceanographic evidence independently confirms reduced overturning during the cooling period, representing a consensus baseline. The strongest opposing consideration is that the precise initiator (meltwater routing vs. volcanism vs. other forcings) remains intensely debated, but the circulation slowdown itself is widely accepted.

Multiple independent paleoproxy lines — including foraminiferal δ18O, deep‑water ventilation proxies, and other ocean indicators — converge on a weakened Atlantic Meridional Overturning Circulation during the Younger Dryas, and this mechanism is widely accepted in neutral reviews (YDIH‑E028). Debate remains over the exact freshwater forcing pathways and magnitudes, but these uncertainties concern trigger details rather than the existence of the circulation change itself. The strongest opposing consideration is that proxy interpretations and models still differ over the precise structure and timing of AMOC changes, but this affects fine‑grained dynamics more than the broad mechanistic consensus.

Lynch-Stieglitz's review records multiple independent paleoceanographic proxy lines for reduced Atlantic overturning during the Younger Dryas, and both camps treat the circulation change as the central proximate mechanism. The claim is the explanandum's mechanism, not evidence for any particular initiator. The strongest opposing consideration is that live technical debate remains over freshwater-forcing routing and magnitude, so even this consensus mechanism is not a closed book. That debate concerns initiation details, not whether overturning weakened.

Multiple independent paleoceanographic proxy lines support reduced Atlantic overturning during the Younger Dryas, the neutral review literature treats the circulation change as the proximate mechanism, and both camps in this dispute stand on it — which is precisely why rejecting an impact trigger requires rejecting nothing about the cooling itself. Strongest opposing consideration: the freshwater-forcing details (routing, magnitude) and the precise degree of AMOC reduction remain technically live, and a 2026 study proposes volcanic forcing — but those debates concern the initiator, not the proximate mechanism this claim asserts. The verdict is partly prior-calibrated from standard paleoceanography, and it is consistent with every record carried in this file.

Multiple independent paleoceanographic proxy lines converge on reduced Atlantic overturning during the Younger Dryas, and a neutral review written outside this controversy treats it as the central proximate mechanism. This is common ground for both camps and does not discriminate between triggers. The strongest opposing consideration is that the freshwater-forcing details and the initiation sequence remain genuinely debated at decadal resolution, which is why I stop short of "established." Nothing in the records challenges the AMOC role itself.

Multiple independent paleoceanographic proxies support AMOC weakening (YDIH-E028), accepted by both camps — and diagnostically inert for the trigger question, which is the question at issue.

Multiple independent paleoceanographic proxies support reduced overturning during the Younger Dryas (YDIH-E028), and both camps accept it. Credible but diagnostically inert on the trigger question the case turns on.

Multiple independent paleoceanographic proxies support reduced overturning during the Younger Dryas (YDIH-E028), and both camps accept it. Credible but diagnostically inert on the trigger question the case turns on.

Multiple independent paleoceanographic proxies support reduced overturning during the Younger Dryas (YDIH-E028), and both camps accept it. It is credible but diagnostically inert on the trigger question that the case turns on.

Multiple independent paleoceanographic proxies support reduced overturning during the Younger Dryas (YDIH-E028), and both camps accept it. Credible but diagnostically inert on the trigger question the case turns on.

Multiple independent paleoceanographic proxies support reduced overturning during the Younger Dryas (YDIH-E028), and both camps accept it. Credible but diagnostically inert on the trigger question the case turns on.

Multiple independent paleoceanographic proxy lines support reduced Atlantic overturning during the Younger Dryas; the review literature treats the circulation change as the central proximate mechanism while leaving the initiating trigger — meltwater routing, sea-ice feedbacks, volcanism, or something else — genuinely open.

Extensive paleoceanographic proxy records firmly establish that a substantial slowdown or reorganization of the Atlantic Meridional Overturning Circulation accompanied the Younger Dryas cold period. This circulation reduction provides the recognized proximate mechanism for North Atlantic cooling and associated hemispheric climate shifts. The strongest opposing consideration is that the exact routing, volume, and trigger of the freshwater forcing necessary to induce this circulation collapse remain unresolved.

The Lynch-Stieglitz review finds multiple independent paleoceanographic proxies supporting reduced AMOC during the Younger Dryas, consistent with the cooling's North Atlantic pattern, and this is common ground between the camps. The strongest opposing consideration is that the initiating freshwater forcing's routing and magnitude remain debated — but that concerns the trigger, not the proximate mechanism this claim asserts.

YDIH-E028 reports multiple independent paleoceanographic proxies supporting reduced or reorganized Atlantic overturning during the Younger Dryas and relates that change to the observed North Atlantic cooling pattern. The evidence addresses the proximate climatic mechanism without determining what initiated it. The strongest opposing consideration is continuing uncertainty over freshwater routing, forcing magnitude, and the exact initiating trigger, none of which negates the supported AMOC reorganization itself.

Multiple independent paleoceanographic proxies converge on reduced Atlantic Meridional Overturning Circulation during the Younger Dryas, matching the North Atlantic cold-reversal pattern. Strongest opposing consideration is residual debate over the exact freshwater routing and magnitude, yet the proximate AMOC reorganization itself is robust.

Lynch-Stieglitz's review reports multiple independent paleoceanographic proxies for reduced Atlantic overturning during the Younger Dryas, consistent with the cold reversal's North Atlantic pattern (E028). The source is neutral on the impact dispute, and its conclusion matches general paleoclimate background, a prior I note but do not need. The claim is common ground for both camps and does not discriminate among initiators, which is why it makes the impact evidentially optional rather than supporting it. Strongest opposing consideration: proxy evidence of reduced overturning during the event shows association more directly than proximate causation; sea-ice and atmospheric feedbacks, or direct volcanic radiative forcing (C508, E029), could share the work, and the initiating trigger is acknowledged to be open.

Multiple independent paleoceanographic proxy lines support reduced Atlantic overturning during the Younger Dryas; the review literature treats the circulation change as the central proximate mechanism while leaving the initiating trigger — meltwater routing, sea-ice feedbacks, volcanism, or something else — genuinely open.