Last Millennium hydro-climate variability in Central–Eastern Europe (Northern Carpathians, Romania)

Abstract

Proxy-based reconstructions of climate variability over the last millennium provide important insights for understanding current climate change within a long-term context. Past hydrological changes are particularly difficult to reconstruct, yet rainfall patterns and variability are among the most critical environmental variables. Ombrotrophic bogs, entirely dependent on water from precipitation and sensitive to changes in the balance between precipitation and evapotranspiration, are highly suitable for such hydro-climate reconstructions. We present a multi-proxy analysis (testate amoebae, plant macrofossils, stable carbon isotopes in Sphagnum, pollen, spores and macroscopic charcoal) from an ombrotrophic peat profile from the Rodna Mountains (northern Romania) to establish a quantitative record of hydro-climatic changes. We identify five main stages: wet surface mire conditions between AD 800 and 1150 and AD 1800 and 1950, and drying of the mire surface between AD 1300 and 1450, AD 1550 and 1750 and AD 1950 and 2012. Our multi-proxy reconstructions suggest that conditions during the Medieval Climate Anomaly (MCA) period (AD 900–1150) were considerably wetter than today, while during most of the ‘Little Ice Age’ (LIA; AD 1500–1850), they were dry. Mire surface conditions in the Rodna Mountains have dried markedly over the last 40 years mainly as a result of anthropogenic climate change approaching the driest conditions seen over the last 1000 years. There is a marked difference between current hydro-climatic conditions (dry mire) and those of the MCA (wet mire). This implies that for the study region, the MCA cannot provide analogous climatic conditions to the contemporary situation. Our reconstructions are in partial agreement with water table estimates elsewhere in central and eastern Europe but generally contrast with those from NW Europe, especially during LIA. We suggest that these distinctive regional differences result from fluctuations in large-scale atmospheric circulation, which determine the relative influences of continental and oceanic air masses.

Late Holocene palaeohydrological changes in a Sphagnum peat bog from NW Romania based on testate amoebae

“…Around 100 cal yr BP dry climatic conditions are suggested by the presence of Difflugia pulex and Nebela militaris. A similar event was described at Tăul Muced by Feurdean et al (2015).…”

“…These very wet conditions persisted until 1150 cal yr BP, the beginning of a period where the wet indicators (Amphitrema flavum and Hyalosphenia papilio) dominated the TA fauna with more than 80% of the total taxa assemblage. This wet peat surface conditions lasted until yr 280 BP and correlates with a gradually wetter conditions described in Tăul Muced profile between 1015 -850 cal yr BP (Feurdean et al, 2015). The transition of the peatland surface vegetation from CarexSphagnum to predominately Sphagnum and the extremely low input of minerogenic material (< 5%) suggests an isolation of the peatland from the other water supplies except precipitation and could by related with the peatland transition from minerotrophic to ombrotrophic.…”

“…To date, in Romania, despite numerous peat bogs that can be excellent archives for testate amoebae (TA) based reconstruction data on fossil TA is limited to only two records (Schnitchen et al, 2006;Feurdean et al, 2015) although palaeoecological studies are abundant (e.g., Fărcaş et al, 2005;Feurdean et al, , 2013Tanţău et al, 2011Tanţău et al, , 2014 This study is focused on a Sphagnum dominated peat bog from Romania and the main objectives will be: i) analysis of testate amoebae fossil assemblages for qualitative reconstruction of the moisture conditions on the peat surface; ii) loss on ignition analysis (LOI) for the calculation of organic matter and minerogenic material content in sediments; iii) to assess the possible correlation between the qualitative reconstruction of the major wet-dry shifts, the content of organic matter and the minerogenic material input.…”

A 9000 year record of cyclic vegetation changes identified in a montane peatland deposit located in the Eastern Carpathians (Central-Eastern Europe): Autogenic succession or regional climatic influences?

“…The age-depth model of this 560 cm sequence was constructed using the smooth spline method as implemented by CLAM software (Blaauw, 2010). In this model, the 14 C AMS age estimates were converted into calendar years BP using the IntCal13 data set of Reimer et al (2013), whereas the 210 Pb age estimates for the top 20 cm were calculated using a Constant Rate of Supply (CRS) model (see Feurdean et al, 2015).…”

Periodic input of dust over the Eastern Carpathians during the Holocene linked with Saharan desertification and human impact

“…Feurdean et al, 2012). More recently, testate amoeba (TA) (Schnitchen et al, 2006;Feurdean et al, 2015), pollen and diatoms (Magyari et al, 2009Buczkó et al, 2013), and macrofossils (Gałka et al, 2016) have been utilised to elucidate the history of hydroclimatic variability in the region. What is evident from these studies is the high inter-site variability, with clear disagreements on timing and extent of wet and dry periods within a relatively small spatial distribution (e.g.…”