Climate Evolution During the Late Glacial and the Holocene

Abstract

The Late Glacial and Holocene dynamics of fluvial and slope erosion in Romania cannot be understood in the absence of well-dated, continuous, and spatially homogenous records of past climate changes. In this chapter, we provide the scientific community with the first compilation of past climate changes during this period in Romania (Central-East Europe). The lack of climate reconstructions from the Eastern and Southern parts of the country restricts our synthesis to the western half of the country, with an emphasis on the high and mid-altitudes (between 200 and 2000 m a.s.l.), where most of the studied sites are located. We are using a combination of speleothem and diatom δ¹⁸O and δ¹³C values, chironomid-inferred July temperatures, tree ring width, and pollen-based quantitative reconstructions to infer the main climatic changes during the last ca. 15,000 years. The data we are using show that, although synchronous within dating uncertainties with similar changes elsewhere in Europe, those in NW and SW Romania were generally less dramatic, with reduced amplitude of air temperature changes. These changes were mostly expressed during the cold season, suggesting frequent changes in seasonality. Precipitation amount decreased markedly at the onset of cold periods (GS–1, 8.2 and 3.2 ka events etc.) suggesting increased continentality. Warming at the end of the Last Glacial was abruptly interrupted by the onset of the cooling at ca. 12,800 cal BP, cooling that lasted until ca. 11,700–11,600 cal BP. The Early Holocene was generally dry and warm, especially in NW Romania, the warmer than present conditions prevailing until the mid-Holocene. After ca. 5000 cal BP, a slow cooling trend towards the present prevailed, punctuated by shorter (ca. 200 years) and longer (>500 years) periods of enhanced cooling, mostly expressed in NW Romania, and not evident in the SW. Also, after 5000 cal BP, a slow increase in the influence of the Mediterranean climate is detectable in SW Romania, possibly expanding towards the NW. The last 1000 years are characterized by a generally warm and dry period lasting until ~ 1300 AD, followed by an erratic (with rapid swings from cold and wet to warm and dry and back) Little Ice Age, between 1300 and 1900 AD.