Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

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 sulfurrich 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 Dryasrelated 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 seaice-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.

Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period

“…All four volcanic eruptions are interpreted as bipolar and they are therefore most likely associated with low-latitude eruptions. This is in conflict with the hypothesis that one of them should be related to the German Laacher See eruption (Baldini et al, 2018) that is believed to have a primarily northern hemispheric fingerprint (Graf and Timmreck, 2001). A tephra layer in the NGRIP ice core occurring close to the oldest of the four spikes has previously been tentatively associated with a Hekla eruption (Mortensen et al, 2005), but with the clear bipolar signature there is likely a temporal overlap between this Icelandic and an additional lower-latitude eruption.…”

“…In Antarctic ice cores, the corresponding Antarctic Isotopic Maxima (AIM) are characteristic warm events that are more gradual and of smaller amplitude than the Greenland events (EPICA community members, 2006). The AIMs are believed to be related to the DO events through the so-called bipolar seesaw mechanism (Bender et al, 1994;Stocker and Johnsen, 2003), but the detailed mechanism is a matter of debate (Landais et al, 2015;Pedro et al, 2018). Knowledge of the exact phasing of climate in the two hemispheres is crucial for deciphering the driving mechanism of the abrupt climate variability of the last glacial period and the climatic teleconnection patterns that connect the two hemispheres.…”

“…Three different techniques have been applied to progressively improve the synchronization of Greenland and Antarctic ice cores: globally well-mixed atmospheric gases -in particular the methane concentration (Blunier et al, 1998;Lemieux-Dudon et al, 2010;Rhodes et al, 2015;WAIS Divide Project Members, 2015) and the isotopic compositions of O 2 -δ 18 O atm (Bender et al, 1994;Capron et al, 2010), cosmogenic isotopes such as 10 Be (Raisbeck et al, 2017;Steinhilber et al, 2012), and the identification of large volcanic eruptions with bipolar sulfate deposition (Sigl et al, 2013;Svensson et al, 2013). A strength of the bipolar methane matching approach is that atmospheric methane concentrations change almost in phase with abrupt Greenland climate change allowing for those events to be synchronized in ice cores.…”

Volcanic origin for Younger Dryas geochemical anomalies ca. 12,900 cal B.P.

“…Laacher See released from 2 to 150 Mt of sulfur. Although under debate, this may have triggered the temperature decline associated with YD climate change in the Northern Hemisphere (10).…”

Assessing the Statistical Uniqueness of the Younger Dryas: A Robust Multivariate Analysis

“…Since then, however, a growing body of geological evidence attributing the Younger Dryas cooling to a glacial outburst flood and/or a change in glacial meltwater drainage patterns to the ocean (Broecker et al, 1989;Clark et al, 2001;Keigwin et al, 2018) has often led to this episode being treated as a unique event, rather than as one of the D-O stadials (Li and Born, 2019). Evidence that the YD cooling also might have coincided with "one-time" events such as a meteorite impact (Firestone et al, 2007) and/or a large volcanic eruption (Baldini et al, 2018) capable of 'blocking out' incoming solar radiation has helped bolster this notion. In this paper, we use a multivariate outlier method to re-examine the extent to which the BA/YD should be considered 'unique' in the context of the other D-O events.…”