17 Jun 2022
17 Jun 2022
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

The 8.2 ka event in northern Spain: timing, structure and climatic impact from a multi-proxy speleothem record

Hege Kilhavn1,2, Isabelle Couchoud1,2, Russell N. Drysdale2, Carlos Rossi3, John Hellstrom2, Fabien Arnaud1, and Henri Wong4 Hege Kilhavn et al.
  • 1EDYTEM, Université Savoie Mont Blanc, 73376 Le Bourget du Lac, France
  • 2School of Geography, Earth and Atmospheric Sciences, The University of Melbourne, 3010 Victoria, Australia
  • 3Dept. Petrología y Geoquímica, Facultad de Ciencias Geológicas, Universidad Complutense, 28040 Madrid, Spain
  • 4Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia

Abstract. The 8.2 ka event is regarded as the most prominent climate anomaly of the Holocene, and is thought to have been triggered by a meltwater release to the North Atlantic that was of sufficient magnitude to disrupt the Atlantic Meridional Overturning Circulation (AMOC). It is most clearly captured in Greenland ice-core records, where it is reported as a cold and dry anomaly lasting ~160 years, from 8.25 ± 0.05 ka BP until 8.09 ± 0.05 ka BP (Thomas et al., 2007). It is also recorded in several archives in the North Atlantic region, however its interpreted timing, evolution and impacts vary significantly. This inconsistency is commonly attributed to poorly constrained chronologies and/or inadequately resolved time series. Here we present a high-resolution speleothem record of early Holocene palaeoclimate from El Soplao Cave in northern Spain, a region pertinent to studying the impacts of AMOC perturbations on south-western Europe. We explore the timing and impact of the 8.2 ka event on a decadal scale by coupling speleothem stable carbon and oxygen isotopic ratios, trace element ratios (Mg / Ca and Sr / Ca) and growth rate. Throughout the entire speleothem record, δ18O variability is related to changes in effective recharge. This is supported by the pattern of changes in δ13C, Mg / Ca and growth rate. The 8.2 ka event is marked as a centennial-scale negative excursion in El Soplao δ18O, starting at 8.19 ± 0.06 ka BP and lasting until 8.05 ± 0.05 ka BP, suggesting increased recharge at the time. Although this is supported by the other proxies, the amplitude of the changes is minor and largely within the realm of variability over the preceding 1000 years. Further, the shift to lower δ18O leads the other proxies, which we interpret as the imprint of the change in the isotopic composition of the moisture source, associated with the meltwater flux to the North Atlantic. A comparison with other well-dated records from south-western Europe reveals that the timing of the 8.2 ka event was synchronous, with an error-weighted mean age for the onset of 8.23 ± 0.03 ka BP and 8.10 ± 0.05 ka BP for the end of the event. This compares favourably with the NGRIP record. The comparison also reveals that the El Soplao δ18O is structurally similar to the other archives in south-western Europe, and the NGRIP ice-core record.

Hege Kilhavn et al.

Status: open (until 12 Aug 2022)

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Hege Kilhavn et al.


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Short summary
The analysis of stable carbon and oxygen isotopic ratios, trace element ratios and growth rate from a Spanish speleothem provides quantitative information about past hydrological conditions during the early Holocene in southwestern Europe. Our data show that the cave site experienced increased effective recharge during the 8.2 ka event. Additionally, the oxygen isotopes indicate a change in the isotopic composition of the moisture source, associated with the meltwater flux to the North Atlantic.