Reconstructing seasonality through stable-isotope and trace-element analyses of the Proserpine stalagmite, Han-sur-Lesse cave, Belgium: indications for climate-driven changes during the last 400 years

Abstract

Abstract. Fast-growing speleothems allow for the reconstruction of palaeoclimate down to a seasonal scale. Additionally, annual lamination in some of these speleothems yields highly accurate age models for these palaeoclimate records, making these speleothems valuable archives for terrestrial climate. In this study, an annually laminated stalagmite from the Han-sur-Lesse cave (Belgium) is used to study the expression of the seasonal cycle in northwestern Europe during the Little Ice Age. More specifically, two historical 12-year-long growth periods (ca. 1593–1605 CE and 1635–1646 CE) and one modern growth period (1960–2010 CE) are analysed on a sub-annual scale for their stable-isotope ratios (δ13C and δ18O) and trace-element (Mg, Sr, Ba, Zn, Y, Pb, U) contents. Seasonal variability in these proxies is confirmed with frequency analysis. Zn, Y and Pb show distinct annual peaks in all three investigated periods related to annual flushing of the soil during winter. A strong seasonal in-phase relationship between Mg, Sr and Ba in the modern growth period reflects a substantial influence of enhanced prior calcite precipitation (PCP). In particular, PCP occurs during summers when recharge of the epikarst is low. This is also evidenced by earlier observations of increased δ13C values during summer. In the 17th century intervals, there is a distinct antiphase relationship between Mg, Sr and Ba, suggesting that processes other than PCP, i.e. varying degrees of incongruent dissolution of dolomite, eventually related to changes in soil activity and/or land-use change are more dominant. The processes controlling seasonal variations in Mg, Sr and Ba in the speleothem appear to change between the 17th century and 1960–2010 CE. The Zn, Y, Pb, and U concentration profiles; stable-isotope ratios; and morphology of the speleothem laminae all point towards increased seasonal amplitude in cave hydrology. Higher seasonal peaks in soil-derived elements (e.g. Zn and Y) and lower concentrations of host-rock-derived elements (e.g. Mg, Sr, Ba) point towards lower residence times in the epikarst and higher flushing rates during the 17th century. These observations reflect an increase in water excess above the cave and recharge of the epikarst, due to a combination of lower summer temperatures and increased winter precipitation during the 17th century. This study indicates that the transfer function controlling Mg, Sr and Ba seasonal variability varies over time. Which process is dominant – either PCP, soil activity or dolomite dissolution – is clearly climate driven and can itself be used as a palaeoenvironment proxy.

Palaeoenvironmental conditions during MIS 6/MIS 5 transition recorded in speleothems from the Tatra Mountains

“…2015; Vansteenberge et al . 2020) or part of the penultimate glacial period (MIS 6; Drysdale et al . 2005) with the exception of the Corchia Cave record in Italy (Drysdale et al .…”

Optimizing sampling strategies in high-resolution paleoclimate records

“…This is a consequence of the assumption that δ 18 O w remains constant yearround and that one knows its true value. Both these assumptions are problematic in the absence of independent evidence of the value of δ 18 O w , especially in deep time settings (see, e.g., Veizer and Prokoph, 2015;Henkes et al, 2018). The risk of this assumption is made clear when comparing cases in which δ 18 O w is indeed constant year-round at the assumed value (0 ‰; e.g., cases 1-6 and 19-24) with cases in which shifts in δ 18 O w occur, especially when these shifts are out of phase with respect to the SST seasonality (e.g., cases 9-11, 18, and 25-33; Fig.…”

“…However, it should warrant caution in using δ 18 O c data for SST reconstructions even in modern settings. Implications for deep time reconstructions are even greater, given the uncertainty and variability in global average (let alone local) δ 18 O w values (Jaffrés et al, 2007;Veizer and Prokoph, 2015). The complications of using δ 18 O c as a proxy for marine temperatures in deep time are discussed in detail in O'Brien et al (2017) and Tagliavento et al (2019).…”

“…These problems are exacerbated by the fact that accurate methods for climate reconstructions may require comparatively large sample sizes or rely on uncertain assumptions. A case in point is the popular carbonate stable oxygen isotope temperature proxy (δ 18 O c ), which relies on assumptions of the water composition (δ 18 O w ) that become progressively more uncertain further back in geological history (e.g., Veizer and Prokoph, 2015). In contrast, the clumped isotope proxy ( 47 ) does not rely on this assumption but requires larger amounts of sample (e.g., Müller et al, 2017) A promising technique for circumventing sample size limitations is to analyze larger numbers of small aliquots from the same sample or from similar parts of the climate archive.…”

ShellChron 0.4.0: a new tool for constructing chronologies in accretionary carbonate archives from stable oxygen isotope profiles

“…Fast-growing carbonate archives, such as coral skeletons, mollusk shells, and speleothems, contain a wealth of information about past and present climate and environment (e.g., Urban et al, 2000;Wang et al, 2001;Steuber et al, 2005;Butler et al, 2013). Recent advances in analytical techniques have improved our ability to extract this information and obtain records of the conditions under which these carbonates precipitated at high temporal resolutions, often beyond the annual scale (Treble et al, 2007;Saenger et al, 2017;Vansteenberge et al, 2020;de Winter et al, 2020a;Ivany and Judd, 2022). Key to the interpretation of such records is the development of reliable chemical or physical proxies for climate and environmental conditions which can be measured on a sufficiently fine scale to allow variability to be reconstructed at the desired time resolution.…”