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

• Published in: Climate of the past Vol. 18; no. 5; pp. 989 - 1009
• Main Authors: Holmes, Dakota E, Babila, Tali L, Ninnemann, Ulysses, Bromley, Gordon, Tyrrell, Shane, Paterson, Greig A, Curran, Michelle J, Morley, Audrey
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 06-05-2022; Copernicus Publications
• Subjects: Boundary conditions; Carbon dioxide; Climate; Climate variability; Cryosphere; Deep sea; Deep sea drilling; Deep water; Deepwater drilling; Drilling; Glacial climates; Glacial periods; Ice sheets; Interglacial periods; Isotopes; Ocean circulation; Overflow; Polar climates; Polar waters; Temperature; Variability; Nordic Seas; Greenland
• ISSN: 1814-9332; 1814-9324; 1814-9332
• DOI: 10.5194/cp-18-989-2022

While a large cryosphere may be a necessary boundary condition for millennial-scale events to persist, a growing body of evidence from previous
interglacial periods suggests that high-magnitude climate events are possible during low-cryosphere climate states. However, the full spectrum of
variability, and the antecedent conditions under which such variability can occur, have not been fully described. As a result, the mechanisms
generating high-magnitude climate variability during low-cryosphere boundary conditions remain unclear. In this study, high-resolution climate
records from Deep Sea Drilling Project (DSDP) site 610 are used to portray the North Atlantic climate's progression through low ice, boundary conditions of Marine Isotope Stage
(MIS) 11c into the glacial inception. We show that this period is marked by two climate events displaying rapid shifts in both deep overflow and
surface climate. The reorganization between Polar Water and Atlantic Water 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 intermediate and low ice boundary conditions,
we find that a reduction in deep water precedes surface hydrographic change. The existence of surface and deep-ocean events, with similar
magnitudes, abruptness, and surface–deep phasing, advances our mechanistic understanding of, and elucidates antecedent conditions that can lead to,
high-magnitude climate instability.