Climatic influences on stable water isotope variability in palaeo-precipitation
Stable water isotopes are useful tracers in the hydrological cycle that preserve integrated histories of water transport. Water isotope archives such as speleothems (calcium carbonate cave deposits) and ice cores provide evidence of past changes in the atmospheric water cycle. Climatic interpretatio...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2018
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| Online Access: | http://hdl.handle.net/1885/150207 https://doi.org/10.25911/5d611be6d3e91 https://openresearch-repository.anu.edu.au/bitstream/1885/150207/5/b25699337_Lewis_Sophie%20Caroline.pdf.jpg |
| Summary: | Stable water isotopes are useful tracers in the hydrological cycle that preserve integrated histories of water transport. Water isotope archives such as speleothems (calcium carbonate cave deposits) and ice cores provide evidence of past changes in the atmospheric water cycle. Climatic interpretations from past isotopic variability in proxy records often consider changes as an index of a single climate parameter, such as temperature or precipitation amount. The isotopic composition of precipitation, however, more accurately integrates multiple variations in atmospheric circulation from source to site. In this study, the impact of abrupt and orbital- scale climatic changes on the tropics and poles is examined using geochemical and modelling techniques. The dominant climatic influences on variability in water isotopes in precipitation are investigated for a variety of different types of climatic change, and the climatic interpretations applied to speleothem and ice core records are evaluated using general circulation model simulations of isotope and climate variability.Results for comparison with proxy records are obtained from a suite of simulations of past and present climates using the coupled atmosphere-ocean Goddard Institute for Space Studies (GISS) ModeIE-R. Water isotope tracers are incorporated into the model and are tracked through all stages of the hydrological cycle, where appropriate fractionations are applied at each phase change. In addition, simulations utilise a novel suite of generalised vapour source distribution (VSD) tracers, whereby the sources of water vapour to a location can be traced back through any cloud process to the site of original surface evaporation. Firstly, geochemical analyses from a speleothem from southern Indonesia are combined with model results to constrain the spatial and temporal evolution of abrupt climate change in the low latitudes. This demonstrates that Heinrich stadial hydrological changes in the southern tropics are more complex than inter-hemispheric anti-phasing ... |
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