https://novaprd-lb.newcastle.edu.au/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:47773 Wed 22 Mar 2023 18:06:21 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:33010 SO₄ =(mSO₄/mCO₃)_solid/(mSO₄/mCO₃)_solution. High crystal growth rates (driven by either pH or saturation state) encouraged higher values of D_SO₄ because of an increasing concentration of defect sites on crystal surfaces. At low growth rates, D_SO₄ was reduced due to an inferred competition between sulphate and bicarbonate at the calcite surface. These experimental results are applied to understand the incorporation of sulphate into speleothem calcite. The experimentally determined pH-dependence suggests that strong seasonal variations in cave air PCO₂ could account for annual cycles in sulphate concentration observed in stalagmites. Our new experimentally determined values of D_SO₄ were compared with D_SO₄ values calculated from speleothem-drip water monitoring from two caves within the Austrian and Italian Alps. At Obir cave, Austria, D_SO₄ (×10⁵) varies between 11.1 (winter) and 9.0 (summer) and the corresponding figures for Ernesto cave, Italy, are 15.4 (winter) and 14.9 (summer). These values approximate predicted D_SO₄ values based on our chamber experiments containing both low (2 ppm) and high (20 ppm) sulphate concentrations. Our experimental values of D_SO₄ obtained at crystal growth rates typical of stalagmites, closely match those observed in other cave sites from around the world. This validates the universality of the controls behind D_SO₄ and will enhance the use of speleothem CAS as a palaeoenvironmental proxy.]]> Tue 03 Sep 2019 18:19:27 AEST ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:45155 18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data–model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.]]> Thu 27 Oct 2022 14:49:38 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:54914 Thu 21 Mar 2024 12:03:59 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:1234 Sat 24 Mar 2018 08:28:33 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:9790 Sat 24 Mar 2018 08:11:04 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:9792 Sat 24 Mar 2018 08:11:03 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:10909 Sat 24 Mar 2018 08:07:41 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:18114 13C values are linked to low δ¹³C values of cave air and drip water during that time. This observation corresponds to times of reduced cave ventilation, high pCO₂ of cave air, low drip water pH, lower calcite supersaturation and typically high drip rates. In contrast, the translucent, dense laminae represent more or less complete lateral coalescence (inclusion-free) during the cold season (high calcite, drip water and cave air δ¹³C values), i.e. times of enhanced cave ventilation, low cave air pCO₂, increased drip water pH, relatively high calcite supersaturation and typically low drip rates. In essence, the relative development of the two lamina types reflects changes in the seasonality of external air temperature and precipitation, with a strong control of the winter air temperature on the intensity of cave-air exchange. Thick translucent, dense laminae are favoured by long, cold and wet winters and such conditions may be related closely to the North Atlantic Oscillation mode (weak westerlies) and enhanced Mediterranean cyclone activity during the cold season. Studies of speleothem lamination can thus help to better understand (and quantify) the role of seasonality changes, for example, during rapid climate events.]]> Sat 24 Mar 2018 08:04:36 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:19953 Sat 24 Mar 2018 07:58:32 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:17998 Sat 24 Mar 2018 07:56:35 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:5010 Sat 24 Mar 2018 07:44:12 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:30183 2 contribution to the total dissolved inorganic carbon (DIC). Pronounced millennial-scale shifts in DCP and relatively small coeval but antipathetic changes in δ¹³C are modulated by the effects of hydrological variability on open and closed-system dissolution, SAD and prior calcite precipitation. Hence, the DCP in Corchia Cave speleothems represents an additional proxy for rainfall amount.]]> Sat 24 Mar 2018 07:41:34 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:26051 230Th relative even to the very low levels of detrital ²³⁰Th present. Here, we present an alternative method for reliable dating of these young speleothems using radiocarbon. Approximately 100 carbonate samples from SC4 and WM7 were analysed for ¹⁴C by accelerator mass spectrometry (AMS). The AMS results indicate that bomb ¹⁴C was evident in the youngest parts of both stalagmites. Two different approaches were used to estimate dead carbon fraction (DCF) values for these stalagmites for the pre-bomb period. For SC4, the DCF values were estimated based on the timing of ¹⁴C dates for that period determined by high-resolution δ¹⁸O recorded in the speleothem, and the timing of the onset of bomb ¹⁴C. For WM7, a “maximum” range of pre-bomb DCF was determined. Chronologies of these speleothems were built based on a dense sequence of DCF-corrected ages using three different age-depth models: Clam (Classical method), and Bacon and OxCal (Bayesian statistical approach). Good agreement between these age-depth models were observed indicating that the top 170 mm of SC4 and the top 50 mm of WM7 grew during the past 550–750 years and 1360–1740 years, respectively.]]> Sat 24 Mar 2018 07:31:29 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:25220 Sat 24 Mar 2018 07:14:01 AEDT ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:50776 Sat 05 Aug 2023 10:05:47 AEST ]]> https://novaprd-lb.newcastle.edu.au/vital/access/manager/Repository/uon:54581 Sat 02 Mar 2024 10:09:26 AEDT ]]>