Winter climatic conditions in Western Carpathian Mountains (Eastern Europe) during last millenium

The aim of this study is to reconstruct winter climatic conditions during Medieval Warm Period (MWP) and LIA (Little Ice Age) based on the stable isotopes analyses on two parallel ice cores extracted from Scărișoara Ice Cave, Romania. Based on the analysis of δ¹⁸O data we identified two distinct periods: a warm Medieval Warm Period, (MWP, between AD 850 and 1250) and a cold the Little Ice Age (LIA, between AD 1450 and 1860), separated by a transition period (between AD 1250 and 1450). Further, deuterium excess (d-excess, d = δ²H-8*δ¹⁸O) indicates that during the MWP, air masses were predominantly originating from a dry source between AD 890 and 1000 (likely the Mediterranean Sea) and a generally wet source after ca. AD 1000 (likely, the Atlantic Ocean and/or the Western Mediterranean Sea). During the Transition Period both air temperature and moisture sources had major fluctuations. During the early LIA,  winters were generally cold and humid, while in the second half, winters were cold and dry. Ice accumulation rates, which are the result of winter accumulation and summer ablation, varied widely during the last 1000 years, with strong melting occurring during periods of increased summer rains and/or reduced winter accumulation. Comparing our data with summer climate reconstructions from the same region suggest that both the warm MWP and the cold LIA were predominantly feature of winter climate variability, summer temperatures being much stable during the last millennium.