North Atlantic Climate Reconstruction during a Warm Event from the Last Glacial Revealed through Geochemical Analysis of a Scottish Flowstone.

Abstract

Dansgaard-Oeschger (DO) warm events were interstadial intervals during the last glacial period characterised by abrupt increases in Northern Hemisphere temperature above background glacial conditions, followed by a gradual return to a stadial state. The mechanisms driving these rapid warming events, their spatial extent, and their influence on global climate cycles remain a focus of current research. Developing a clearer understanding of the triggers and controls of past climate states is critical for improving interpretations of contemporary forcing mechanisms and their cascading impacts on climate variability. This research presents new evidence for DO-12 warming at higher latitudes than previously recognised, based on a new flowstone chronology from Scotland. This chronology aligns well with SIOC19, supporting its adoption as the dominant chronology for the last glacial period. A novel method for reconstructing palaeotemperature and hydrological variability is introduced, derived from the temperature dependency of DMg and the degree of Prior Calcite Precipitation (PCP) occurring within the flowstone analogue. The reconstructed temperature range is notably large, with one possible explanation being the presence of an alternative subarctic climate regime in Scotland during DO-12. Spectral analysis of NAO-band cycles identifies a potential dampened meridional temperature gradient and stronger subtropical forcing during DO-12, attributed to northwards shifts in key Atlantic climate mechanisms. Overall, the results of this study contribute to a refined understanding of DO-12, its timing and spatial influence, the behaviour of the NAO under abrupt warming, and the resultant impacts on European climate. More broadly, this research enhances knowledge of climate cycle dynamics and the thresholds and cascade effects associated with rapid forcing changes, providing new insight into how these processes manifested during the last glacial period