DID ENHANCED WINTERTIME MERIDIONAL CIRCULATION CONTRIBUTE TO A WETTER MEDITERRANEAN ALTITHERMAL?: STABLE-ISOTOPE PROXY EVIDENCE FROM KINDERLINSKAYA CAVE, RUSSIA

Numerous paleoclimatic proxies point to a relatively late Holocene Climatic Optimum in the Eastern Mediterranean region (~9.5–5.5 ka), which was characterized by much higher precipitation compared to the remainder of the Holocene. Specifically, speleothem records from Sofular Cave (northern Turkey) and Soreq Cave (Israel) constrain the timing of this phenomenon, alongside various pollen records, but the seasonality of excess rainfall is still widely debated. Orbitally forced monsoon dynamics have been cited as a cause of more frequent summer storms (as in northern Africa), but it has been argued that relatively strong Hadley circulation would have inhibited formation of the so-called ‘Mediterranean depression’, consistent with palynological evidence for summer aridity. Alternatively, it is plausible that precipitation increased primarily during winter, when the region receives most of its rain, but the mechanism for this shift remains unknown. Stable-isotope analysis of two stalagmites from Kinderlinskaya Cave in the southern Urals provide a continuous Holocene record of winter climate (11.9 ka to present) for the continental interior of western Eurasia. By comparing our record to that of Sofular Cave in Turkey, we offer a novel approach to quantifying atmospheric circulation dynamics affecting western Eurasia, which utilizes the isotopic gradients between proxies for δ¹⁸O in winter precipitation. The analysis indicates that the Mediterranean altithermal was coincident with enhanced Scandinavian blocking patterns that promote meridional wintertime flow over easternmost Europe and across Anatolia, similar to the positive phase of the modern North Sea–Caspian Pattern. This mode of circulation is associated with cooler temperatures and stronger rainfall over northern Turkey, Israel, the Aegean Sea, and the Middle East, which may partially explain nearly ubiquitous climate signal from these regions during the Holocene Climatic Optimum and reconcile conflicting interpretations of its seasonality.