Abstract
Abstract. The Toba eruption that occurred some 74 ka ago in Sumatra, Indonesia, is among the largest volcanic events on Earth over the last 2 million years. Tephra from this eruption has been spread over vast areas in Asia, where it constitutes a major time marker close to the Marine Isotope Stage 4/5 boundary. As yet, no tephra associated with Toba has been identified in Greenland or Antarctic ice cores. Based on new accurate dating of Toba tephra and on accurately dated European stalagmites, the Toba event is known to occur between the onsets of Greenland interstadials (GI) 19 and 20. Furthermore, the existing linking of Greenland and Antarctic ice cores by gas records and by the bipolar seesaw hypothesis suggests that the Antarctic counterpart is situated between Antarctic Isotope Maxima (AIM) 19 and 20. In this work we suggest a direct synchronization of Greenland (NGRIP) and Antarctic (EDML) ice cores at the Toba eruption based on matching of a pattern of bipolar volcanic spikes. Annual layer counting between volcanic spikes in both cores allows for a unique match. We first demonstrate this bipolar matching technique at the already synchronized Laschamp geomagnetic excursion (41 ka BP) before we apply it to the suggested Toba interval. The Toba synchronization pattern covers some 2000 yr in GI-20 and AIM-19/20 and includes nine acidity peaks that are recognized in both ice cores. The suggested bipolar Toba synchronization has decadal precision. It thus allows a determination of the exact phasing of inter-hemispheric climate in a time interval of poorly constrained ice core records, and it allows for a discussion of the climatic impact of the Toba eruption in a global perspective. The bipolar linking gives no support for a long-term global cooling caused by the Toba eruption as Antarctica experiences a major warming shortly after the event. Furthermore, our bipolar match provides a way to place palaeo-environmental records other than ice cores into a precise climatic context.
Highlights
1.1 Linking of Greenland and Antarctic ice core recordsSynchronization of palaeo-environmental records in ice cores from Greenland and Antarctica has long been a topic of great interest
The approach taken here to establish the bipolar Toba link takes two steps: first, we provide an estimate for the position of the Toba eruption in the NGRIP and EDML ice cores based on recent independent dating of the event and on the bipolar seesaw hypothesis
In the study of Storey et al (2012), the precise Toba dating of several samples cluster around the age of 73.88±0.32 ka BP, and in the study of Mark et al (2013) ages fall in the range of 75.0 ± 0.9 ka BP, but the temporal resolution of the Ar-Ar technique does not exclude the existence of several Toba eruptions separated by centuries
Summary
1.1 Linking of Greenland and Antarctic ice core recordsSynchronization of palaeo-environmental records in ice cores from Greenland and Antarctica has long been a topic of great interest. Bender et al (1994) used the global signal of oxygen isotopes of air trapped in the Greenland GISP2 and the Antarctic Vostok ice cores to link the two climatic records during the last glacial period. Because air bubbles are incorporated in ice cores at the depth where firn is compacted to ice, the age of the ice and the age of the gas record in an ice core are offset by the so-called “delta age” (Schwander et al, 1993; Buizert et al, 2012). Uncertainties of the order of 100–1000 yr remain in synchronizing ice core climatic signals using gas-based matching (Blunier et al, 2007)
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