Monitoring of a fast-growing speleothem site from the Han-sur-Lesse cave, Belgium, indicates equilibrium deposition of the seasonal δ<sup>18</sup>O and δ<sup>13</sup>C signals in the calcite

Abstract

Abstract. Speleothems provide paleoclimate information on multimillennial to decadal scales in the Holocene. However, seasonal or even monthly resolved records remain scarce. Such records require fast-growing stalagmites and a good understanding of the proxy system on very short timescales. The Proserpine stalagmite from the Han-sur-Less cave (Belgium) displays well-defined/clearly visible darker and lighter seasonal layers of 0.5 to 2 mm thickness per single layer, which allows a measuring resolution at a monthly scale. Through a regular cave monitoring, we acquired a good understanding of how δ 18 O and δ 13 C signals in modern calcite reflect climate variations on the seasonal scale. From December to June, outside temperatures are cold, inducing low cave air and water temperature, and bio-productivity in the soil is limited, leading to lower pCO 2 and higher δ 13 C values of the CO 2 in the cave air. From June to December, the measured factors display an opposite behavior.The absence of epikarst water recharge between May and October increases prior calcite precipitation (PCP) in the vadose zone, causing drip water to display increasing pH and δ 13 C values over the summer months. Water recharge of the epikarst in winter diminishes the effect of PCP and as a result the pH and δ 13 C of the drip water gradually decrease. The δ 18 O and δ 13 C signals of fresh calcite precipitated on glass slabs also vary seasonally and are both reflecting equilibrium conditions. Lowest δ 18 O values occur during the summer, when the δ 13 C values are high. The δ 18 O values of the calcite display seasonal variations due to changes in the cave air and water temperature. The δ 13 C values reflect the seasonal variation of the δ 13 C DIC of the drip water, which is affected by the intensity of PCP. This same anticorrelation of the δ 18 O versus the δ 13 C signals is seen in the monthly resolved speleothem record that covers the period between 1976 and 1985 AD. Dark layers display lower δ 18 O and higher δ 13 C values. The cave system varies seasonally in response to the activity of the vegetation cover and outside air temperature between a "summer mode" lasting from June to December and a "winter mode" from December to June. The low δ 18 O and high δ 13 C values of the darker speleothem layers indicate that they are formed during summer, while light layers are formed during winter. The darker the color of a layer, the more compact its calcite structure is, and the more negative its δ 18 O signal and the more positive its δ 13 C signal are. Darker layers deposited from summer drip water affected by PCP are suggested to contain lower Ca 2+ concentration. If indeed the calcite saturation represents the main factor driving the Proserpine growth rate, the dark layers should grow slower than the white layers.

Cave monitoring in the Béke and Baradla caves (Northeastern Hungary): implications for the conditions for the formation cave carbonates

“…1; Hungarian Meteorological Service). Total annual precipitation was 725 mm, 684 mm, and 527 mm for 2013, 2014, and 2015 Table 1). Based on the data recorded at the meteorological station at Jósvafő the mean annual temperature was 9.6°C, 10.6°C, and 10.4°C for 2013, 2014, and 2015, respectively.…”

“…The broadly negative relationship O deviation, left vertical axis). Black filled circles: published data (Daeron et al, 2011;Tremaine et al, 2011;Moreno et al, 2014;Van Rampelbergh et al, 2014).Grey line: calcitewater (cc-w) oxygen isotope fractionation (δ 18 O (cc-w) , right vertical axis) as a function of pH calculated by Watkins et al (2014) for 25°C. Uncertainties of sample points are based on the analytical uncertainties of pH and δ…”

Transfer of environmental signals from the surface to the underground at Ascunsă Cave, Romania

“…Drȃguşin et al: Transfer of environmental signals by-case calibration of speleothem proxies against climate parameters and were employed throughout the world: Gibraltar (Mattey et al, 2008), Belgium (Verheyden et al, 2008;Van Rampelbergh et al, 2014), France (Genty et al, 2014), the Czech Republic (Faimon et al, 2012), Spain (Smith et al, 2016;Dumitru et al, 2017), Austria (Spötl et al, 2005), Germany (Riechelmann et al, 2013), USA (Onac et al, 2008;Feng et al, 2014;Meyer at al., 2014), Australia (Jex et al, 2012) or China (Hu et al, 2008;Duan et al, 2016). Such studies focus mainly on parameters such as cave air temperature and relative humidity, CO 2 concentration in drip water and cave atmosphere, or stable isotope ratios in drip water and modern calcite.…”

A 500-year seasonally resolved δ<sup>18</sup>O and δ<sup>13</sup>C, layer thickness and calcite aspect record from a speleothem deposited in the Han-sur-Lesse cave, Belgium

“…An absolute age model is established by combining layer-counting ages with measured U / Th ages. A comparison of variations in layer thickness, calcite aspect, δ 18 O and δ 13 C signals in light of previous studies (Genty and Quinif, 1996;Verheyden, 2001;Genty et al, 2003;Mühlinghaus et al, 2007;Boch et al, 2009;Wackerbarth et al, 2010;Fohlmeister et al, 2012;Verheyden et al, 2014) and monitoring of the same stalagmite location (Van Rampelbergh et al, 2014) leads to a better understanding of how these proxies are related and how they reflect climate variations. Comparing the Proserpine climate signal with winter temperature reconstructions in Europe (Le Roy Ladurie, 2004;Luterbacher et al, 2004;Dobrovolny et al, 2010) further verifies the proposed climate interpretation.…”

“…While the temperature displays a well-marked seasonality with cool summers and mild winters, the rainfall is spread over the entire year. The external seasonality in temperature causes a subdued temperature variation within the Salle-du-Dôme of 2 to 2.5 • C between summer and winter (Van Rampelbergh et al, 2014). Present-day calcite is deposited in isotopic equilibrium with its drip water (Van Rampelbergh et al, 2014).…”