Double negative peak of the 8.2 ky event and subsequent &#8222;overshoot&#8221; recorded in speleothems from Central Europe
Authors: Czuppon György , Demény Attila , Leél-Össy Szabolcs , Óvári Mihály , Lin Ke , Molnár Mihály , Karlik Máté , Siklósy Zoltán , Shen Chuan-Chou Shen 
Published: March 2024

Several short-term climate anomalies occurred during the Holocene, of which the 8.2 k.y. event was the most pronounced. Several proxy records ranging from the North Atlantic to monsoonal regions indicate that this event had a semi-global impact. The release of large amounts of freshwater into the North Atlantic has been cited as a major cause of the slowing of oceanic thermohaline circulation (von Grafenstein et al., 1998; Barber et al., 1999), resulting in this climate perturbation. Despite the significance of this event, high-resolution speleothem records are relatively scarce (e.g. Duan et al., 2023; Wood et al., 2023). These high-resolution oxygen isotope records from eastern China to South America revealed the complex structure of the 8.2 ky event.Here we present two high-resolution oxygen isotope records from Central Europe (B&#233;ke Cave, NE Hungary and Vacska Cave N Hungary), along with the chemical data of calcite and the hydrogen isotope composition of inclusion-hosted water. The high-resolution oxygen isotope time series reveals a double negative anomaly around 8.2 k.y., whereas a positive anomaly appears in the following period (8.1 k.y.). Similar patterns are also observed in the hydrogen isotope data series. Assuming that the temperature change was solely responsible for the observed systematics, this data is utilized to calculate the relative temperature increase/decrease. Apparently, a 1-1.5&#176;C temperature decrease for the 8.2 k.y. event and a 2&#176;C increase for the &#8220;overshoot&#8221; around 8.1 k.y. can be given. Moreover, the oxygen isotope composition may be affected not only by temperature but also by changes in the amount of precipitation and/or its seasonality, as well as by the shifting of the main route of moisture transportation (Atlantic vs. Mediterranean moisture sources). Calculated d-excess values might indicate some changes during these periods. Additionally, trace element composition suggests a shift in summer/winter precipitation amounts for the overshoot.We are thankful for the support and permission of the Aggtelek National Park Directorate and the Duna-Ipoly National Park Directorate. The J&#225;nos Bolyai Research Scholarship of the Hungarian Academy of Sciences financially supported Gy&#246;rgy Czuppon&#8217;s work.Barber D.C, Dyke A., Hillaire-Marcel C., Jennings A. E., Andrews J. T., Kerwin M. W., Bilodeau G., McNeely R., Southon J., Morehead M. D., Gagnon J.-M. (1999) Forcing of the cold event of 8,200 years ago by catastrophic drainage of Laurentide lakes. Nature, 400, 344-348.Duan, P., Li, H., Ma, Z., Zhao, J., Dong, X., Sinha, A., et al. (2023). Interdecadal to centennial climate variability surrounding the 8.2 ka event in North China revealed through an annually resolved speleothem record from Beijing. Geophysical Research Letters, 50(1), e2022GL101182.von Grafenstein U., Erlenkeuser H., M&#252;ller J., Jouzel J. Johnsen S. (1998): The cold event 8200 years ago documented in oxygen isotope records of precipitation in Europe and Greenland. Climate Dynamics 14 : 73&#8212;81.Wood, C. T., Johnson, K. R., Lewis, L. E., Wright, K., Wang, J. K., Borsato, A., et al. (2023). High-resolution, multiproxy speleothem record of the 8.2 ka event from Mainland Southeast Asia. Paleoceanography and Paleoclimatology, 38, e2023PA004675.