Reconstruction of environmental and hydroclimate changes in the Adriatic region over the last 367 kyr from Modrič Cave (Croatia) speleothems

Abstract

We report the longest episodic stable isotope (δ¹⁸O, δ¹³C) speleothem record from the eastern Adriatic coast, obtained from three U-Th dated speleothems from Modrič Cave (Croatia), covering environmental changes at orbital (glacial-interglacial cycles) and sub-orbital (millennial-to-centennial) time scales. According to the age models, speleothems grew intermittently during the last 367 ka, i.e. the time span from Marine Isotope Stage (MIS) 10 to the present, with growth episodes during 367-342 ka, 331-278 ka, 244-233 ka, 200-155 ka, 69-34 ka and from 15 ka to the present. Speleothem deposition during every interglacial and glacial period, except for the MIS 8, along with the isotope record, suggest that intermittent calcite deposition was not entirely climate controlled, but depended upon the drip site specifics, as well.

As for the speleothem isotopic signal, δ¹³C variations were governed by local soil bioactivity, while the δ¹⁸O signal was a proxy for regional hydroclimate processes. As commonly found in the Mediterranean, δ¹⁸O was controlled by precipitation amount, except during the three detected periods when the source effect outweighed the amount effect. Most likely, due to the weakened Atlantic Meridional Overturning Circulation (AMOC), ¹⁸O-depleted Atlantic moisture was partially compensated with ¹⁸O-enriched Mediterranean-sourced moisture. Regional teleconection between the North Atlantic region and the central Mediterranean has been characterized by a rapid response to abrupt climate system reorganization during Termination TI. Although future anthropogenic climate changes will occur under different boundary conditions, understanding the persistence of such rapid, dynamic teleconnections over longer time scales is of significant interest to the climate community.