Decoupled winter and summer climate changes in southern Europe during the Dansgaard-Oeschger cycles
Résumé
The marine isotope stage 3 (MIS 3) (similar to 60-30 ka) exhibits large amplitude millennial climatic oscillations, also named Dansgaard-Oeschger (DO) cycles, which are marked by alternation of warm (GIs - Greenland interstadials) and cold phases (GSs-Greenland stadials). Here, we explore the seasonal nature of the DO cycle climate signal in southern Europe using 12 pollen records that allowed us to reconstruct the vegetation types and key climatic parameters such as seasonal temperatures and precipitation. Our results show the development of arboreal vegetation during GIs and non-arboreal vegetation during GSs. They also indicate that vegetation changes were mainly driven by winter precipitation and temperatures, with high and low values during GIs and GSs, respectively. The results tend to demonstrate a decoupling between winter and summer conditions, with relatively stable and warm summer temperatures throughout MIS 3, but large amplitude variations in winter. We infer that the climate over southern Europe was mainly influenced by surface conditions over the North Atlantic driven by stratification due to meltwater discharge, and also possibly by extension/contraction of the subpolar gyre (SPG) through changes in the westerlies' strength, thus impacting the extent of winter sea-ice cover, temperature and moisture availability over southern Europe.
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