Abstract
Abstract. The Younger Dryas is considered the archetypal millennial-scale climate change event, and identifying its cause is fundamental for thoroughly understanding climate systematics during deglaciations. However, the mechanisms responsible for its initiation remain elusive, and both of the most researched triggers (a meltwater pulse or a bolide impact) are controversial. Here, we consider the problem from a different perspective and explore a hypothesis that Younger Dryas climate shifts were catalysed by the unusually sulfur-rich 12.880 ± 0.040 ka BP eruption of the Laacher See volcano (Germany). We use the most recent chronology for the GISP2 ice core ion dataset from the Greenland ice sheet to identify a large volcanic sulfur spike coincident with both the Laacher See eruption and the onset of Younger Dryas-related cooling in Greenland (i.e. the most recent abrupt Greenland millennial-scale cooling event, the Greenland Stadial 1, GS-1). Previously published lake sediment and stalagmite records confirm that the 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 sulfate aerosol cooling was amplified by ocean circulation shifts and/or sea ice expansion, gradually cooling the North Atlantic region and incrementally shifting the midlatitude westerlies to the south. The aerosol-related cooling probably only lasted 1–3 years, and the majority of Younger Dryas-related cooling may have been due to the sea-ice–ocean circulation positive feedback, which was particularly effective during the intermediate ice volume conditions characteristic of ∼ 13 ka BP. We conclude that the large and sulfur-rich Laacher See eruption should be considered a viable trigger for the Younger Dryas. However, future studies should prioritise climate modelling of high-latitude volcanism during deglacial boundary conditions in order to test the hypothesis proposed here.
Highlights
The Younger Dryas (YD) climate anomaly occurred during the last deglaciation and is often described as a brief return to near-glacial conditions in northern Europe
It is apparent that the clearest hydroclimatic expression of the YD in central Europe lags behind Greenland cooling associated with Greenland Stadial (GS)-1 by 170 years (Fig. 4)
The Laacher See eruption (LSE) preceded the most clearly expressed dynamical climatic change associated with the YD in central Europe, its timing (12.880 ± 0.040 ka BP) is indistinguishable from the Greenland temperature decrease leading into GS-1, beginning at 12.870 ± 0.138 ka BP (Rach et al, 2014; Steffensen et al, 2008; Rasmussen et al, 2014)
Summary
The Younger Dryas (YD) climate anomaly occurred during the last deglaciation and is often described as a brief return to near-glacial conditions in northern Europe. The identification of the Vedde Ash chronostratigraphic unit within Meerfelder Maar (Germany) lake sediments has improved correlations with Greenland ice core records, which contain the same ash (Lane et al, 2013a) This revised chronological framework strongly suggests that the 12.880 ka BP Laacher See eruption was synchronous with cooling associated with the YD onset (i.e. the most recent abrupt Greenland millennial-scale cooling event, the Greenland Stadial 1, GS-1) but preceded major atmospheric circulation shifts over central Europe (Rach et al, 2014). More research is clearly needed to thoroughly investigate this hypothesis, the apparent coincidence of a large, very sulfur-rich eruption with the beginning of YD cooling is compelling and well worth exploring further
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