Stable isotopes in cave ice suggest summer temperatures in east-central Europe are linked to Atlantic Multidecadal Oscillation variability

Abstract

Abstract. The climate of east-central Europe (ECE) is the result of a combination of influences originating in the wider North Atlantic realm, the Mediterranean Sea, and the western Asian and Siberian regions. Previous studies have shown that the complex interplay between the large-scale atmospheric patterns across the region results in strongly dissimilar summer and winter conditions on timescales ranging from decades to millennia. To put these into a wider context, long-term climate reconstructions are required, but, largely due to historical reasons, these are lacking in ECE. We address these issues by presenting a high-resolution, radiocarbon-dated record of summer temperature variations during the last millennium in ECE, based on stable isotope analysis of a 4.84 m long ice core extracted from Focul Viu Ice Cave (Western Carpathians, Romania). Comparisons with both instrumental and proxy-based data indicate that the stable isotope composition of cave ice records the changes in summer air temperature and has a similar temporal evolution to that of the Atlantic Multidecadal Oscillation on decadal to multidecadal timescales, suggesting that changes in the North Atlantic are transferred, likely via atmospheric processes towards the wider Northern Hemisphere. On centennial timescales, the data show little summer temperature differences between the Medieval Warm Period (MWP) and the Little Ice Age (LIA) in eastern Europe. These findings are contrary to those that show a marked contrast between the two periods in terms of both winter and annual air temperatures, suggesting that cooling during the LIA was primarily the result of wintertime climatic changes.

Record summer rains in 2019 led to massive loss of surface and cave ice in SE Europe

“…Over the past decade, various proxies in cave ice have been used to reconstruct temperature variability during the Holocene (Perşoiu et al, 2017;Sancho et al, 2018;Badaluta et al, 2020), vegetation dynamics (Feurdean et al, 2011;Leunda et al, 2019) and atmospheric composition (Kern et al, 2009(Kern et al, , 2011. Additionally, other studies have targeted the microbial and fungal communities harbored by cave ice, identifying dormant new species (Brad et al, 2018;Itcus et al, 2018;Paun et al, 2019;Mondini et al, 2019). Unfortunately, research to date has targeted only a handful of ice caves, with the vast majority of existing ones harboring a yet unexplored wealth of information (Perşoiu and Lauritzen, 2018).…”

A Review of Ice Core Drilling in Cave Environment – Challenges, Achievements and Future Directions

“…These early efforts were continued in 20th century, with varying degrees of success, mostly due to difficulties in building reliable chronologies of ice accumulation . Thus, cave ice-based studies addressed the geochemistry and stable isotope geochemistry of cave ice (Kern et al, 2009;Kern et al, 2011a;Kern et al, 2011b;May et al, 2011), the dynamics of past winter (Perșoiu et al, 2017) and summer (Bădăluţă et al, 2020) air temperatures, past environmental and vegetation changes (Feurdean et al, 2011;Sancho et al, 2018;Leunda et al, 2019) and the dynamics of cave ice accumulations (Stoffel et al, 2009;Perșoiu and Pazdur, 2011;Spötl et al, 2014;. Over the past few years, several studies investigated microorganism in cave ice deposits, with specifically designed drilling strategies (Sattler et al, 2013;Itcus et al, 2018) allowing the recovery of millennia-old microbial (Mondini et al, 2019;Paun et al, 2019) and fungal (Brad et al, 2018) communities.…”

“…Poor ventilation in caves further excluded the usage of on-spot generated electric energy (health risk and cave pollution impact due to stagnation of exhaust fume). In a special situation a generator was operated outside the Focul Viu Ice Cave (Maggi et al, 2008;Bădăluţă et al, 2020). Thus, due to limitations in access to the caves, manual augers were usually the only available drilling option.…”

“…Clastic debris is produced by periglacial processes leading to intense weathering of the cave walls and continuous accumulation (and subsequent incorporation in ice) of pieces of limestone of varying sizes. Cave ice drilling projects frequently reported that such rocky (Luetscher et al, 2007;Vrana et al, 2007;Sattler et al, 2013;Bădăluţă et al, 2020) or woody (Kern et al, 2004;2011b) debris embedded in the ice caused problems or completely stopped the drilling effort. The coarse rocky debris can wear out the cutting edge of the auger in a relative short time, so an easily replaceable cutting teeth system can be required in the field (see section 4.1).…”

“…To address these challenges, we have developed 1) a dedicated drilling device for cave glaciers (Murariu et al, 2013) and 2) a "Cave Ice Sedimentary architecture and deposition (CISAD)" approach to investigating subterranean cave ice deposits. This approach has been used in several past (Perşoiu et al, 2017;Bădăluţă et al, 2020) and ongoing studies in caves in Romania, Norway, Greece, Slovakia, Slovenia, Croatia etc.…”