EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Open Access Biogeosciences Biogeosciences Discussions Open Access Open Access Clim. Past, 9, 377–391, 2013 Climate www.clim-past.net/9/377/2013/ Climate doi:10.5194/cp-9-377-2013 of the Past of the Past © Author(s) 2013. CC Attribution 3.0 License. Discussions Open Access Open Access Earth System Earth System Dynamics Dynamics Discussions Reconstruction of drip-water δ18O based on calcite oxygen and Open Access Geoscientific Geoscientific Open Access clumped isotopes of speleothems from Bunker CaveInstrumentation (Germany) Instrumentation T. Kluge1, H. P. Affek1, T. Marx2, W. Aeschbach-Hertig2, D. F. C. Riechelmann3, D. ScholzMethods4, S. Riechelmann and 5, Methods and A. Immenhauser5, D. K. Richter5, J. Fohlmeister6, A. Wackerbarth6, A. Mangini6, andData C. Sp otl¨Systems7 Data Systems 1Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT, 06511, USA Discussions Open Access Open Access 2Institut fur¨ Umweltphysik, Universitat¨ Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany Geoscientific 3Geographisches Institut, Johannes Gutenberg-Universitat¨ Mainz, Johann-Joachim-Becher-WegGeoscientific 21, 55099 Mainz, Germany 4 Model Development Institut fur¨ Geowissenschaften, Johannes Gutenberg-Universitat¨ Mainz, Johann-Joachim-Becher-WegModel Development 21, 55099 Mainz, Germany Discussions 5Institut fur¨ Geologie, Mineralogie und Geophysik, Ruhr-Universitat¨ Bochum, Universitatsstraße¨ 150, Open Access 44801 Bochum, Germany Open Access 6Heidelberger Akademie der Wissenschaften, Im Neuenheimer Feld 229, 69120 Heidelberg,Hydrology Germany and Hydrology and 7 Institut fur¨ Geologie und Palaontologie,¨ Leopold-Franzens-Universitat¨ Innsbruck, InnrainEarth 52, 6020 System Innsbruck, Austria Earth System Correspondence to: T. Kluge ([email protected]) Sciences Sciences Received: 21 June 2012 – Published in Clim. Past Discuss.: 24 July 2012 Discussions Open Access Revised: 27 December 2012 – Accepted: 13 January 2013 – Published: 14 February 2013 Open Access Ocean Science Ocean Science Abstract. The geochemical signature of many speleothems Eemian: −7.6 ± 0.2 ‰ and the Holocene Climatic Optimum: Discussions used for reconstruction of past continental climates is af- −7.2 ± 0.3 ‰). This new approach offers a unique possibil- fected by kinetic isotope fractionation. This limits quanti- ity for quantitative climate reconstruction including the as- Open Access tative paleoclimate reconstruction and, in cases where the sessment of past hydrological conditions whileOpen Access accounting kinetic fractionation varies with time, also affects relative for disequilibrium effects. Solid Earth paleoclimate interpretations. In carbonate archive research, Solid Earth Discussions clumped isotope thermometry is typically used as proxy for absolute temperatures. In the case of speleothems, however, clumped isotopes provide a sensitive indicator for disequilib- 1 Introduction Open Access Open Access rium effects. The extent of kinetic fractionation co-varies in Speleothems provide an increasingly popular archive for ter- 1 and δ18O so that it can be used to account for disequilib- 47 restrial paleoclimate reconstruction, with their oxygen iso- The Cryosphere rium in δ18O and to extract the past drip-water composition. The Cryosphere tope signals recording variations in cave temperature and Discussions Here we apply this approach to stalagmites from Bunker local rainfall (e.g., McDermott, 2004; Fairchild and Baker, Cave (Germany) and calculate drip-water δ18O values for w 2012). The isotopic composition of snow and rain (δ18O, the Eemian, MIS3, and the Holocene, relying on indepen- δD) reveals important details about the hydrological cycle dent temperature estimates and accounting for disequilib- such as the source region of water vapor, storm trajecto- rium. Applying the co-variation method to modern calcite ries, and the conditions during vapor condensation and rain- precipitates yields drip-water δ18O values in agreement w out (Clark and Fritz, 1997; Aggarwal et al., 2005; Lachniet, with modern cave drip-water δ18O of −7.9 ± 0.3 ‰, de- w 2009). The rainfall δ18O values often show a temperature spite large and variable disequilibrium effects in both cal- w dependence that is particularly pronounced in the mid and cite δ18O and 1 . Reconstructed paleo-drip-water δ18O c 47 w high latitudes. The largest temperature dependence of δ18O values are lower during colder periods (e.g., MIS3: −8.6 ± w was observed in polar stations (0.8–0.9 ‰ ◦C−1; Dansgaard, 0.4 ‰ and the early Holocene at 11 ka: −9.7 ± 0.2 ‰) and 1964; Rozanski et al., 1993). In mid-latitudes moderate val- show higher values during warmer climatic periods (e.g., the ues were measured (0.53–0.69 ‰ ◦C−1, Dansgaard, 1964; Published by Copernicus Publications on behalf of the European Geosciences Union. 18 18 378 T. Kluge et al.: Drip-water δ O reconstruction using 147-δ O co-variance Rozanski et al., 1993; Gourcy et al., 2005), whereas low lat- to reconstruct paleotemperatures from a flowstone in Vil- 18 itudes or marine sites show only a low temperature depen- lars Cave (France) using drip-water δ Ow determined from dence of 0.17 ‰ ◦C−1 (Rozanski et al., 1993). speleothem fluid inclusions, resulting in reasonable tempera- The modern-day spatial temperature dependence of oxy- ture estimates (Wainer et al., 2011). Here we use the opposite 18 gen isotopes in rainfall is commonly used as calibration for approach to reconstruct δ Ow values in paleo-rainfall. 18 paleoclimatic applications, e.g., for polar ice cores (Lorius In this study we present the first paleo-drip-water δ Ow et al., 1985; Johnsen et al., 1992; Grootes et al., 1993) and record based on the clumped isotope co-variation method. speleothems (Duplessy et al., 1970; Dorale et al., 1992), with We investigate the reproducibility of the signals and check the aim to reconstruct past temperature changes. The basic the overall precision and the applicability of the method for 18 18 assumption for these applications is that the δ Ow-T rela- drip-water δ Ow reconstruction by measuring temporally tionship is constant over time. However, noble gas studies in overlapping stalagmites that grew during the last glacial cy- groundwater (Loosli et al., 2001; Varsany´ et al., 2011) sug- cle in Bunker Cave (Germany). The potential and limitations gest that this relationship was different in the past, at least of the approach are assessed using modern calcite precip- regionally. Similar deviations between the modern spatial itated in the cave in comparison with monitoring data of 18 δ Ow-T relationship and the temporal reconstructions were Bunker Cave. also observed for polar ice cores by comparison with inde- pendent temperature calibrations (Cuffey et al., 1995; Sever- inghaus et al., 1998). Both examples highlight the need for 2 Study site and samples an improved understanding of the δ18O -T relationship and w Bunker Cave (51◦220 N, 7◦400 E) is located in the Middle to its temporal variability. This requires reliable reconstruction Upper Devonian limestone of the Rhenish Slate Mountains of both paleotemperature and rainfall isotopes. (Germany) at about 180 m above sea level and is overlain Speleothems are the potentially ideal candidates for rain- by 15–30 m of karstified limestone bedrock. The meteoro- fall δ18O reconstruction due to the possibility of high- w logical conditions in the region are dominated by North At- precision age determination, high-resolution stable isotope lantic pressure systems, with a temperate climate, precipita- measurements, and their ability to faithfully retain climatic tion throughout the year (annual mean 900 mm, 1961–1990), signals (e.g., Gascoyne, 1992; McDermott, 2004; Fairchild and a mean annual air temperature of 9.5 ◦C (1961–1990). and Baker, 2012). Complications arise from disequilibrium The air temperature in the last two decades has increased to effects that often influence δ18O and δ13C values (Mickler c about 10.5 ◦C (1988–2007, German Meteorological Service et al., 2006; Demeny´ et al., 2010; McDermott et al., 2011; DWD); a change that is also observed in the cave tempera- Tremaine et al., 2011; Riechelmann et al., 2012) and have ture. During the cave monitoring period 2006–2011, a mean been recently shown to influence also clumped isotope val- temperature of 10.8 ◦C was measured in Bunker Cave. Drip- ues (Affek et al., 2008; Meckler et al., 2009; Daeron¨ et al., water δ18O values are rather constant at −7.9 ± 0.3 ‰ for 2011; Wainer et al., 2011; Kluge and Affek, 2012). Contrary w all stalagmite-related monitoring sites within Bunker Cave. to the early suggestion of a constant disequilibrium offset (in The study uses four stalagmites (BU1, BU2, BU4, BU- Soreq Cave; Affek et al., 2008), Kluge and Affek (2012) ob- UWE) from Bunker Cave that grew through the Holocene served temporal variations in the degree of kinetic isotope (past 8.2 ka – BU1, BU4), the early Holocene (∼ 11 ka – fractionation that preclude the use of constant disequilibrium BU2, BU-UWE), marine isotope stage (MIS) 3 (BU2,