Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.737876
Title: El Niño Southern Oscillation from the pre-instrumental era : development of logbook-based reconstructions and evaluation of multi-proxy reconstructions and climate model simulations
Author: Barrett, Hannah G.
ISNI:       0000 0004 7225 3920
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2017
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Abstract:
El Niño Southern Oscillation (ENSO) is a major mode of climatic variability which impacts weather patterns around the globe on inter-annual timescales. This thesis explores ENSO during the pre-instrumental period in order to gain a better understanding of its behaviour on longer time scales than available from the instrumental record. Firstly, the wind observations from ships' logbooks are used to reconstruct a new index of ENSO for the period, 1815-1854. New methods for assessing the robustness of these types of reconstructions which use limited data availability are presented. The logbook-based ENSO reconstructions are then compared to a range of existing ENSO reconstructions over this historical period. It is found that there is disagreement between the various ENSO reconstructions in the early-to-mid nineteenth century and that the majority of the reconstructions are biased towards identifying El Niño events compared to La Niña events, and towards identifying Eastern Pacific El Niño events compared to Central Pacific El Niño events. Historical reanalysis products are used to explore ENSO variability over the twentieth century and provide a data source for comparison with historical climate model simulations. The number and quality of observations assimilated into the historical reanalysis increases through the twentieth century, thus the agreement in ENSO indices is weaker earlier in this period. Historical- (1900-2004 AD) and paleo- (850-1848 AD) climate model simulations are used to assess ENSO further back in time, showing that the strength and character of ENSO-wind teleconnections vary over the Last Millennium. The results from this thesis suggest that there are still a number of uncertainties associated with the range of data types used: the observations from ships' logbooks, documentary records, multi-proxy reconstructions, reanalysis data and global climate model simulations. Only once these have been addressed can current and future ENSO behaviour be placed within its true historical context.
Supervisor: Jones, Julie ; Bigg, Grant Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.737876  DOI: Not available
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