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.

Highlights

  • High-magnitude climate events have long been attributed exclusively to glacial climate states (McManus et al, 1999b)

  • The first event at 397 ka begins with a decrease in Wyville Thomson Ridge Overflow Waters (WTOW) flow speeds (397.43 ± 0.25 ka) over a ~710 ± 90-year period (Fig. 6; for estimation 340 of uncertainties linked to the duration of events and offsets see section 2.11)

  • Sea surface temperature (SST) remain low for 960 ± 210 years and both cooling steps are accompanied by an increase in Ice Rafted Debris (IRD) of 100 grains.g-1 and 1155 grains.g-1 respectively (Fig. 6)

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Summary

Introduction

High-magnitude climate events have long been attributed exclusively to glacial (intermediate-to-large cryosphere) climate states (McManus et al, 1999b). This is scientifically significant and socially relevant 35 because it implies that warm (small cryosphere) climates are inherently more stable than cold climates and that the cryosphere is the chief amplifier of climate variability in the Earth system. This concept emerges primarily from the vantage of millennial-scale variability in the Earth system, which is greatest during glacial periods but minor during interglacials.

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