Abstract
Among abundant reconstructions of Holocene climate in Europe, only a handful has addressed winter conditions, and most of these are restricted in length and/or resolution. Here we present a record of late autumn through early winter air temperature and moisture source changes in East-Central Europe for the Holocene, based on stable isotopic analysis of an ice core recovered from a cave in the Romanian Carpathian Mountains. During the past 10,000 years, reconstructed temperature changes followed insolation, with a minimum in the early Holocene, followed by gradual and continuous increase towards the mid-to-late-Holocene peak (between 4-2 kcal BP), and finally by a decrease after 0.8 kcal BP towards a minimum during the Little Ice Age (AD 1300–1850). Reconstructed early Holocene atmospheric circulation patterns were similar to those characteristics of the negative phase of the North Atlantic Oscillation (NAO), while in the late Holocene they resembled those prevailing in the positive NAO phase. The transition between the two regimes occurred abruptly at around 4.7 kcal BP. Remarkably, the widespread cooling at 8.2 kcal BP is not seen very well as a temperature change, but as a shift in moisture source, suggesting weaker westerlies and increased Mediterranean cyclones penetrating northward at this time.
Highlights
Weather and climate patterns in East-Central Europe (ECE) are strongly influenced by the dynamics of the storm tracks carrying moisture from the North Atlantic Ocean and Mediterranean Sea towards the continent
The relative contribution of these sources is controlled by the strength of the North Atlantic Oscillation (NAO) and East Atlantic-Western Russia (EA-WR) pattern modes of atmospheric variability and the blocking activity of the Siberian High13, 14. δ18O and δ2H values of local precipitation plot along a Local Meteoric Water Line being defined by the equation δ2H = 7.9*δ18O + 8.1415, similar to the Global Meteoric Water Line[16, 17]
We suggest that the cooling in the North Atlantic during the 8.2 ka event led to a weakening of the Icelandic Low and of the westerlies, allowing for more Mediterranean-derived precipitation to reach Scărișoara Ice Cave (SIC)
Summary
Weather and climate patterns in East-Central Europe (ECE) are strongly influenced by the dynamics of the storm tracks carrying moisture from the North Atlantic Ocean and Mediterranean Sea towards the continent. Climate models suggest a poleward shift in the position of mid-latitude storm tracks due to increased warming[3] Under this scenario, central and south Eastern Europe are influenced by subtropical high pressure cells, which heighten risk of droughts[4] and stronger cyclones[5]. Climate in ECE is strongly seasonal, with hot and dry summers associated with the northward expansion of mid-latitude anticyclonic cells, coupled with cold and wet winters, resulting from complex interplay of southward outbursts of Siberian cold air and northward intrusion of moisture carried by Mediterranean cyclones The latter originate in the Western and Central Mediterranean, and their path is heavily influenced by the strength of the North Atlantic Oscillation (NAO), one of the principal modes of climate variability in the Northern Hemisphere[11], defined as the difference of atmospheric pressure between the Icelandic Low and Azores High. By analyzing the isotopic composition of precipitation, drip and lake water, and resulting ice, our previous studies[21] have shown that the isotopic signature of the ice block reflects precipitation from autumn through early winter and related climatic information
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