Stalagmite-inferred hydroclimate changes in northern Italy during Allerød/Younger Dryas transition

<p>The Younger Dryas (YD), a 1200-year-long cooling event interrupting the warm B&#248;lling-Aller&#248;d period, started from 12,870 &#177; 30 yr BP (2&#963;, before 1950 C.E.). Here we present decadal-resolved stalagmite BA18-2 multi-proxy records from B&#224;sura cave, northern Italy. The StalAge age-depth model with 8 U-Th dates with 2-sigma errors of &#177; 26-193 yrs shows that BA18-2 encompasses Aller&#248;d/YD transition, from 14,038 &#177; 92 to 12,090 &#177; 54 yr BP. Oxygen isotope data fluctuate between -7.16&#8240; and -3.68&#8240;, with a clear 2.4&#8240; increase during the YD onset at 12,870 &#177; 30 yr BP. Stalagmite BA18-2 Sr/Ca and Ba/Ca linger from 0.060-0.085 mmol/mol and 6.4-9.1 &#181;mol/mol, respectively, from 14,038 &#177; 92 to 12,681 &#177; 55 yr BP, ~ 2 centuries after the beginning of YD. A clear 160-year-long two-step increase in both Sr/Ca and Ba/Ca records started from 12,681 &#177; 55 yr BP, which is a 200-yr lag relative to the timing of BA18-2 oxygen isotope increasing trend. We argue that the oxygen isotope could be governed by temperature, moisture source, and/or rainfall amount; while, the Sr/Ca and Ba/Ca ratios predominantly reflect precipitation change. Our results might suggest asynchronous thermal and hydrological changes in northern Italy during the Aller&#248;od/YD transition.</p>