Please use this identifier to cite or link to this item: https://apo.ansto.gov.au/dspace/handle/10238/9632
Title: How weather cand climate influences speleothem growth and paleo-climate isotopic records
Authors: Waring, CL
Hankin, SI
Keywords: Paleoclimatology
Weather
Caves
Geogolic structures
Climates
Carbon dioxide
Air
Issue Date: 7-Jul-2020
Publisher: Geological Society of Australia
Citation: Waring, C., & Hankin, S. (2014). How weather cand climate influences speleothem growth and paleo-climate isotopic records. Paper presented at the AESC 2014 (22nd Australian Geological Convention), Newcastle, New South Wales, July 7 - 10.
Series/Report no.: 0729 011 X;
Abstract: Speleothem growth band variations in chemical and isotopic composition are used to infer paleo-climatic conditions. Interpretation of speleothem paleoclimatic records may be improved by matching analysed subsamples to the represented elapsed time and prevailing weather or climatic conditions. Analysed subsamples may represent a month for rapid growth speleothems or many years for slow speleothem growth. Speleothem growth may also be seasonally biased affecting the paleo-climate record. To better understand the temporal fine scale of speleothem growth patterns we have principally used CO2 concentration in cave air. As CaCO3 is precipitated to accrete a new speleothem layer, CO2 is released into the atmosphere. However, CO2 may also come from other sources. To discriminate between different sources a real-time isotopic CO2 analyser, located near the entrance to Chifley Cave, is used. Cave air is sequentially sampled for 10mins from 4 internal and 2 external locations and analysed for H2O, CH4, CO2, and 13CCO2. The 3 principal sources of CO2 are external air, speleothem growth and soil-air. The proportion of each CO2 source contributing to the total cave air CO2 is calculated for each sampled Chifley Cave location. CO2 exhaled from passing tour groups is often recorded as a minor rapid increase before subsiding to the previous background levels over 10–15 mins. Cave air CO2 shows a seasonal (summer maximum) and often a diurnal cycle, from a minimum late morning to a maximum in the late evening caused by ventilation of external low CO2 air. Differences between the external temperature and the near constant cave air temperature causes a buoyancy contrast which drives bidirectional cave air ventilation. On hot days cool cave air (11°C) sinks into the Grand Arch and is replenished by sucking external air from the Plughole cave opening. The slightly lower cave atmospheric pressure on hot days also causes soil-air rich in CO2 to seep into Chifley Cave, notably at the bottom of Katies Bower. On cold winter days relatively buoyant warm cave air escapes via the Plughole 70 m above and through minor fissures reversing the summer pattern. A detailed description (10 min sampling for 2 years) of the speleothem growth pattern in response to external temperature variation is presented.
Gov't Doc #: 9558
URI: http://aesc2014.gsa.org.au/assets/Various-reg-partner-opp-workshop-summ-/AESC-Abstract-Proceedings.pdf
http://apo.ansto.gov.au/dspace/handle/10238/9632
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