Reorganization of Atlantic waters at sub-polar latitudes linked to deep water overflow in both glacial and interglacial climate states

Abstract. Abrupt climate events are generally attributed as a characteristic of glacial (intermediate-to-large cryosphere) climate states. While a large cryosphere may be a necessary boundary condition for millennial-scale events to persist, it remains unclear whether high-magnitude climate variability is purely a glacial phenomenon requiring cryosphere-driven feedbacks. High-resolution climate records are used to portray North Atlantic climate's progression through low-ice, interglacial boundary conditions of Marine Isotope Stage (MIS) 11c into the glacial inception. We show that this period is marked by rapid shifts in both deep overflow and surface climate. The reorganization between polar and Atlantic waters at subpolar latitudes appears to accompany changes in the flow of deep water emanating from the Nordic Seas, regardless of magnitude or boundary conditions. Further, during both glacial and interglacial boundary conditions, we find that a reduction in deep water precedes surface hydrographic change. The existence of surface and deep ocean events during an interglacial, with similar magnitudes, abruptness, and surface-deep phasing as their glacial counterparts, alters our concept of “warm” climate stability and the requisite cryospheric thresholds and feedbacks for it.