The timing, duration and magnitude of the 8.2 ka event in global speleothem records

Abrupt events punctuate the climate of the Holocene epoch, providing valuable insight into rapid climate change. The most notable abrupt event of the Holocene was the 8.2 ka event, when a large influx of meltwater into the North Atlantic reduced northward heat transport in this region. The event provides valuable insight into the global climate response to North Atlantic freshening. Here, we examine the timing, duration and magnitude of the climate response using a global network of speleothem oxygen isotope (δ¹⁸O) records.

Firstly, we objectively identified abrupt climate events in 402 globally distributed speleothem records from the SISAL (Speleothem Isotopes Synthesis and AnaLysis) database (Atsawawaranunt et al., 2018; Comas-Bru et al., 2020) during the Holocene. Secondly, we examined the timing, duration and anomalies of the 8.2 ka δ¹⁸O excursions using 70 speleothem δ¹⁸O records.

We show that the 8.2 ka event is the most globally coherent and significant abrupt event of the last 12,000 years, with an abrupt δ¹⁸O excursion identified in >70% of speleothem records. The δ¹⁸O anomalies are regionally homogeneous; they are negative across Europe and the Mediterranean, positive across Asia, and negative in South America and southern Africa. The excursion is not registered in the Indonesia/Australia region. The median timing of the event from the speleothem records is 8223 ±12 to 8062 ±14 years BP, indistinguishable from the timing in Greenland ice cores of 8247 to 8086 ± 47 years BP (Thomas et al., 2007). The median duration of the 8.2 ka event excursion in speleothems is 159 ±11 years, indistinguishable from the duration in Greenland of 160.5 ± 5.5 years (Thomas et al., 2007). There is no significant difference between the timing and duration in regions both near (Europe) and far (Asia) from the North Atlantic. This globally synchronous timing and duration supports a rapid and widespread climate response, likely via rapid atmospheric teleconnections.

 

Atsawawaranunt, K., et al., 2018. The SISAL database: a global resource to document oxygen and carbon isotope records from speleothems. Earth System Science Data, 10(3), pp.1687-1713.

Comas-Bru, L., et al., 2020. SISALv2: a comprehensive speleothem isotope database with multiple age–depth models. Earth System Science Data, 12(4), pp.2579-2606.

Thomas, E.R., Wolff, E.W., Mulvaney, R., Steffensen, J.P., Johnsen, S.J., Arrowsmith, C., White, J.W., Vaughn, B. and Popp, T., 2007. The 8.2 ka event from Greenland ice cores. Quaternary Science Reviews, 26(1-2), pp.70-81.