The last deglaciation in Italy: timing and pattern from a precisely dated stalagmite

The last deglaciation (Termination I, T-I) was the most recent global-scale climate transition. It involved a drastic temperature increase guiding massive melting of ice sheets, with a concurrent reorganization of inter- and intrahemispherical atmospheric and ocean circulation patterns. T-I lasted ~3.0 ka (ka = kiloyears before present) in Greenland (NGRIP, 2007), although it was not a linear process. A rapid temperature increase at 14.6±0.3 ka (Bølling-Allerød, BA) was followed by a return towards glacial-like conditions (12.2±0.3 ka, Younger Dryas, YD), before the last warming that led to the Holocene (11.7±0.1 ka). Other secondary climate oscillations characterized T-I too (Cheng et al., 2020). Some of these intra-deglaciation global warmings were particularly rapid, at times occurring at centennial or even decadal timescale. This provides an interesting comparison with the current climate change. Yet, it is not clear how T-I-related dynamics occurring at the polar regions and/or in the oceans impacted terrestrial environment at mid latitudes, in terms of rainfall and temperature variation and related environmental and ecological changes. This is especially true for the Mediterranean area, considering that its climate is connected – and controlled – by processes occurring in the Atlantic and Arctic. In Italy, T-I records of adequate chronological resolution are virtually absent. We here present a novel speleothem record from Sant’Angelo Cave (SA1, Ostuni, Apulia) spanning from 47.7±0.1 to 8.9±0.9 ka. In the period from ~20 to ~10 ka, multiple U-Th datings (n=22) resulted in a final age model with an average uncertainty of <0.3 ka and a resolution of ~25 years. Climate proxies (δ18O, n=1045) were anchored to this chronology. The reliability of SA1-δ18O in recording palaeoclimate information was ascertained by a statistically grounded inter-cave replication test with a recently published speleothem record from a nearby site (Columbu et al., 2020). The interpretation of SA1 allows to: 1) accurately and precisely constrain, for the first time in Italy, the timing of the T-I climate pattern; 2) evaluate the impact of BA, YD and Holocene inception in southern Italy, as well as other associated events, especially in terms of rainfall variability; and 3) understand the spatio-temporal relation between the Atlantic/Greenland domain, the Mediterranean realm and monsoonal areas throughout the deglaciation. We discuss this new record within the framework of previous regional studies based on glacial (NGRIP, 2007), marine (Martrat et al., 2007) and continental proxies (Allen et al., 1999; Cheng et al., 2016), with the aim of providing a better comprehension of the timing and structure of T-I in Italy and, by extension, of the central and western Mediterranean area. Allen J.R.M., Brandt U., Brauer A., Hubbertens H.W., Huntley B., Keller J., Kraml M., Meckeen A., Mingram J., Negendank J.F.W., Nowaczyk N.R., Oberhansli H., Watts W.A., Wulf S. & Zolitschka B. (1999) - Rapid environmental changes in southern Europe during the last glacial period. Science, 400, 740-743. Cheng H., Edwards R.L., Sinha A., Spötl C., Yi L., Chen S., Kelly M., Kathayat G., Wang X. & Li X. (2016) - The Asian monsoon over the past 640,000 years and ice age terminations. Nature, 534, 640. Cheng H., Zhang H., Spötl C., Baker J., et al. (2020) - Timing and structure of the Younger Dryas event and its underlying climate dynamics. Proceedings of the National Academy of Sciences, 117, 23408-23417. Columbu A., Chiarini V., Spötl C., Benazzi S., Hellstrom J., Cheng H. & De Waele J. (2020) - Speleothem record attests to stable environmental conditions during Neanderthal-Modern Human turnover in Southern Italy. Nature Ecology & Evolution, 4, 1188-1195. Martrat B., Grimalt J.O., Shackleton N.J., de Abreu L., Hutterli M.A. & Stocker T.F. (2007) - Four climate cycles of recurring deep and surface water destabilizations on the Iberian margin. Science, 317, 502-507. NGRIP, North Greenland Ice Core Project Members. (2004) - High-resolution record of Northern Hemisphere climate extending into the last interglacial period. Nature, 431, 147-151.