Sub-millennial scale climatic oscillations in the central Adriatic during the Lateglacial: palaeoceanographic implications

A multi-proxy study of a sedimentary core obtained from the central Adriatic basin provides evidence of short-term events of palaeoceanographic variability during the last glacial Lateglacial period (GRIP event stages GI-1 and GS-1). Comparison of the Adriatic results with other Mediterranean records reveals a common sequence of changes in palaeoceanographic conditions. Variations in foraminiferal assemblage data and in stable isotopic compositions indicate two short-term cold oscillations, which interrupted an overall cooling trend that commenced at the beginning of the Greenland GI-1 episode (Bolling/Allerod episode). These cold events, considered to be contemporaneous with GI-1b and GI-1d of the GRIP ice-core record, are indicated by distinctive foraminiferal assemblages, which reflect episodes of high productivity under relatively restricted water circulation, with (in particular) reduced vertical mixing during winter. Differences in the foraminiferal assemblages indicate that the younger of the two cold spells is characterized by reduced ventilation of bottom waters. Our results, combined with published data from neighbouring marine basins, suggest a widespread reduction in deep-water formation in the central Mediterranean which commenced during the GI-1b episode and reached its maximum effect during the onset of the GS-1 (Younger Dryas) episode. Moreover, three intervals with reduced vertical mixing correspond to the two cold spells during GI-1 and the lower phase of the GS-1 episode and show close similarities with the palaeoceanographic changes reported for the North Atlantic. This similarity indicates that the Mediterranean and North Atlantic may have been responding more-or-less synchronously to common forcing mechanisms.