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

Abstract

Abstract. Annually laminated speleothems allow the reconstruction of paleoclimate down to a seasonal scale. 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) content. Seasonal variability in the 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 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 varying degrees of incongruent dissolution of dolomite control the observed seasonal variations. 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 and higher drip water discharge 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 or dolomite dissolution, is clearly climate-driven and can thus be used as a paleoclimate proxy itself.

What we talk about when we talk about seasonality – A transdisciplinary review

“…Seasonality is generally expressed in speleothems via 1238 physical and chemical laminations, e.g. annual banding, similar to tree-rings or varves in lacustrine sediments [583]. or CO 2 degassing dynamics, which control stalagmite growth rates [78,52,32,401].…”

“…or CO 2 degassing dynamics, which control stalagmite growth rates [78,52,32,401]. Thus, stalagmite laminae can 1250 be related to i) petrographic/crystallographic changes (such as matrix fabric, crystal density, density of inclusions, crys-1252 tallization pattern [193,359,374]), ii) variations of element content [56,35,359,583], iii) changes in luminescence and 1254 fluorescence, due to presence or absence of organic acids [27,25,527,579], iv) alteration of the number, distribution 1256 density, or size of fluid inclusions [499], or v) changes in the isotopic composition of the carbonate [359,388,468], to name just a few.…”

“…One of the most prominent types of layering in stalagmites results from changes in the crystallographic or mineralogical build-up (i.e., crystal fabric, aragonite vs. calcite), which is easily recognizable. Often, growth layers vary seasonally between white, porous, columnar, and translucent, dense, compact laminae, with the latter being thinner compared to the former [208,52,359,5,583]. Occasionally, growth layers vary seasonally between fibrous aragonite and columnar calcite [460].…”

ShellChron 0.2.8: A new tool for constructing chronologies in accretionary carbonate archives from stable oxygen isotope profiles

“…Urban et al, 2000;Wang et al, 2001;Steuber et al, 2005;Butler et al, 2013). Recent advances in analytical techniques have improved our capability to extract this information and obtain records of the conditions under which these carbonates precipitated at high time resolutions, often beyond the annual scale (Treble et al, 2007;Saenger et al, 2017;Vansteenberge et al, 2019;de Winter et al, 2020a). 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.…”

Optimizing sampling strategies in high-resolution paleoclimate records

“…corals, mollusks and speleothem records) are in high demand in the paleoclimate community, because the seasonal cycle is the most important cycle in Earth's climate and seasonality reconstructions complement more common long-term (kyr to -Myr) records of past climate variability (e.g. Morgan and van Ommen, 1997;Tudhope et al, 2001;Steuber et al, 2005;Steffensen et al, 2008;Denton et al, 2005;Huyghe et al, 2015;Vansteenberge et al, 2019). A more detailed understanding of climate dynamics at the human timescale is increasingly relevant for improving climate projections (IPCC, 2013).…”