Re-evaluating the link between the Laacher See volcanic eruption and the Younger Dryas

Abstract

Abstract. The Younger Dryas is the most well-documented millennial-scale cooling event of the Quaternary, but the mechanisms responsible for its initiation remain elusive. Here we use a recently revised chronology for the GISP2 ice core ion dataset to identify a large volcanic sulphur spike coincident with both the sulphur-rich Laacher See volcanic eruption and the onset of Younger Dryas-related cooling (GS-1) in Greenland. Lake sediment and stalagmite records confirm that the 10 eruption's timing was indistinguishable from the onset of cooling across the North Atlantic, but that it preceded westerly wind repositioning over central Europe by ~200 years. We suggest that the initial short-lived volcanic sulphate aerosol cooling was amplified by oceanic circulation shifts or sea ice expansion, gradually cooling the North Atlantic region and incrementally shifting the mid-latitude westerlies to the south. The aerosol-related cooling probably only lasted 2-4 years, and the majority of Younger Dryas-related cooling was instead due to this positive feedback, which was particularly 15 effective during the intermediate ice volume conditions characteristic of ~13 ka BP. We conclude that the large and sulphurrich Laacher See eruption should be considered a viable trigger for the Younger Dryas.