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Title: Modelling the impact of orbital forcing on late Miocene climate : implications for the Mediterranean Sea and the Messinian Salinity Crisis
Author: Marzocchi, Alice
ISNI:       0000 0004 5994 4516
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2016
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Orbital forcing is a dominant climate driver on multi-millennial time scales, as it modulates the seasonal distribution of incoming solar radiation on the Earth's surface. Geological evidence of orbitally-forced cyclicity is found globally in numerous sedimentary sequences, especially in marginal basins such as the Mediterranean Sea. In the late Miocene (11.61-5.33 Ma), a large portion of the North African catchment is thought to have drained in the Mediterranean Sea, as the main fresh water input into the basin, regulated by precessional changes the North Arican summer monsoon. The distinctive sedimentary cyclicity observed in the Mediterranean Sea is thought to result from the basins biogeochemical response to oscillations in its hydrologic budget, which represents the balance between inflowing (precipitation and river input) and outflowing (evaporation) water, and exchange with other basins. Yet until now, most of the hypotheses about the phasing between orbital forcing and Mediterranean cyclic sedimentary sequences, through changes in the hydrology, are largely untested. The global late Miocene proxy record is sparse and patchy, but the majority of the data are concentrated in the Mediterranean region, which contains palaeoarchives with an exceptionally high temporal resolution. This thesis combines a unique ensemble of numerical simulations through a full precession cycle with the interpretation of geological data; with this experimental design, model results can be compared directly to the Mediterranean sedimentary record. This enables the testing and quantification of a variety of processes relative to past extreme environmental changes in this region, such as the Messinian Salinity Crisis. Seasonal changes in the North Arican monsoon and in the Mediterraneans hydrologic fluxes are explored on precessional timescales, but additional orbitally-driven moisture sources affecting the basin are also investigated. Implications for the sedimentary record are drawn globally and regionally for both the Mediterranean Sea and the Paratethys (the precursor of the Black and Caspian seas). In addition, this work emphasises the reduction in the global model-data mismatch for the late Miocene when orbital variability is included in the climate simulations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available