The Potential of Speleothems from Western Europe as Recorders of Regional Climate: a Critical Assessment of the SISAL Database

Abstract

Western Europe is the region with the highest density of published speleothem δ18O (δ18Ospel) records worldwide. Here we review these records in light of the recent publication of the Speleothem Isotopes Synthesis and Analysis (SISAL) database [1]. We investigate how representative the spatial and temporal distribution of the available records is for climate in Western Europe, and review potential sites and strategies for future studies. We show that spatial trends in precipitation δ18O are mirrored in the speleothems, providing means to better constrain the factors influencing δ18Ospel at a specific location. Coherent regional δ18Ospel trends are found over stadial-interstadial transitions of the last glacial, especially in high altitude Alpine records. Over the Holocene, regional trends are less clearly expressed, due to lower signal-to-noise ratios in δ18Ospel, but can potentially be extracted with the use of statistical methods. Overall, this first assessment highlights the potential of the European region for speleothem palaeoclimate reconstruction, while underpinning the importance of knowledge of local factors for a correct interpretation of δ18Ospel.

Main controls on the stable carbon isotope composition of speleothems

“…This database was compiled to provide a comprehensive understanding of speleothem δ 18 O and δ 13 C records for climate reconstruction and model evaluation (e.g., Comas-Bru et al, 2019). From this database, several papers have already been published that assess data coverage and investigate regional patterns in stalagmite δ 18 O records from specific regions and continents (e.g., Lechleitner et al, 2018;Oster et al, 2019;Braun et al, 2019;Burstyn et al, 2019). To constrain the governing processes influencing speleothem δ 13 C values in the SISAL records we focus on two subsets of the data of the SISAL_v1 database.…”

Speleothem Stable Isotope Records from Eastern Europe & Turkey

“…This likely reflects the relatively short distances involved. The existence of the SISAL database provides an opportunity to go beyond regional data syntheses to examine spatial patterns at a much larger scale [101]. Spatial scale is not an issue for the examination of elevation gradients, and here the data from Eastern Europe provide clear-cut evidence for elevational gradients in δ 18 Ospe during the Holocene (-0.26‰ 100m -1 ).…”

“…The robustness of this empirical δ 18 Ospel gradient can be further explored extending the region of towards nearby SISAL regions, e.g. [101].…”

U-Th and radiocarbon dating of calcite speleothems from gypsum caves (Emilia Romagna, North Italy)

“…The rejection of a large number of U-Th ages is not a common practice in speleothem science (Fairchild & Baker, 2012); speleothems are usually inclined to produce insequence stratigraphic ages because the stable cave environment reduces the possibility of diagenesis, which may reopen the geochemical system with respect to uranium and thorium. However, in a recent comprehensive review regarding western European speleothems used for proxy-based palaeoclimate research (Lechleitner et al, 2018), it has been outlined that 13% of all ages were excluded…”