A Multidisciplinary Approach to Late Quaternary Paleoclimatology with an Emphasis on Sub-Saharan West Africa and the Last Interglacial Period

Persistent Link:
http://hdl.handle.net/10150/238647
Title:
A Multidisciplinary Approach to Late Quaternary Paleoclimatology with an Emphasis on Sub-Saharan West Africa and the Last Interglacial Period
Author:
McKay, Nicholas Paul
Issue Date:
2012
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Embargo:
Release after 09-Jul-2014
Abstract:
A primary goal of paleoclimatology is to extend the instrumental record to capture a wider range of natural variability, documenting the climate system's response to past changes that have no analog in the historical record. Sediment archives of the recent geologic past, both marine and lacustrine, offer the opportunity to study how climate responds to a range of forcings and changing boundary conditions on timescales ranging from years to millennia. In this dissertation I use lacustrine and marine sediment to investigate changes late Quaternary climate, with particular focus on the Last Interglacial period (LIG). First, I use multiple approaches to reconstruct long-term changes in the West African Monsoon by investigating centennial-scale hydrologic variability recorded in Lake Bosumtwi sediments over the past 530,000 years. Over this interval, hydrology in the region is driven by a complex interplay of orbital forcing and glacial-interglacial boundary conditions. Lake level was generally much lower between 50 and 300 ka, likely due to the redistribution of rainfall from the tropics to the subtropics, driven by eccentricity's amplification of precession. Consequently, the Holocene highstand at the lake was both larger and longer lived than the maximum highstand during the LIG.Annual layers were continuously deposited through the LIG in Lake Bosumtwi, and I also present a new, 12,100 year-long, varve record spanning the interval from 128.6 to 116.5 ka. Over the course of the LIG, lake level generally tracks sea surface temperatures (SST) in Gulf of Guinea, including an abrupt drop in lake level that lasted about 500 years ca. 118 ka, coincident with cool SSTs in the North Atlantic and severe aridity in Europe. I find that the despite the generally drier conditions, hydrology varied on similar timescales as the late Holocene, with pronounced multidecadal to centennial-scale variability with non-stationary periodicities. I also investigate the contribution of ocean thermal expansion to sea level rise during the LIG, using a synthesis of paleoceanographic data and a climate model simulation. Globally, LIG SSTs were similar to, or slightly cooler than late Holocene SSTs, with the exception of the North Atlantic, which was several degrees warmer. Consequently, thermal expansion was likely a minor component of sea level rise during the interval, explaining between -0.3 and 0.4 m. of the 6 to 8 m highstand. Lastly, I tested the potential of Raman spectroscopy as a new, non-destructive technique to rapidly measure oxygen isotopic ratios in carbonates at extremely high resolution. Analyses on a suite a synthetic calcites indicate that ¹⁸O/¹⁶O ratios can be measured directly from the Raman spectra and have a 1:1 correspondence with traditional mass-spectrometry measurements. At present, the technique does not have the precision necessary to record natural variability, although there is considerable potential for improving the precision of the technique.
Type:
text; Electronic Dissertation
Keywords:
Last Interglacial; Sahel; Geosciences; Eemian; Intertropical Convergence Zone
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Geosciences
Degree Grantor:
University of Arizona
Advisor:
Overpeck, Jonathan T.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleA Multidisciplinary Approach to Late Quaternary Paleoclimatology with an Emphasis on Sub-Saharan West Africa and the Last Interglacial Perioden_US
dc.creatorMcKay, Nicholas Paulen_US
dc.contributor.authorMcKay, Nicholas Paulen_US
dc.date.issued2012-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.releaseRelease after 09-Jul-2014en_US
dc.description.abstractA primary goal of paleoclimatology is to extend the instrumental record to capture a wider range of natural variability, documenting the climate system's response to past changes that have no analog in the historical record. Sediment archives of the recent geologic past, both marine and lacustrine, offer the opportunity to study how climate responds to a range of forcings and changing boundary conditions on timescales ranging from years to millennia. In this dissertation I use lacustrine and marine sediment to investigate changes late Quaternary climate, with particular focus on the Last Interglacial period (LIG). First, I use multiple approaches to reconstruct long-term changes in the West African Monsoon by investigating centennial-scale hydrologic variability recorded in Lake Bosumtwi sediments over the past 530,000 years. Over this interval, hydrology in the region is driven by a complex interplay of orbital forcing and glacial-interglacial boundary conditions. Lake level was generally much lower between 50 and 300 ka, likely due to the redistribution of rainfall from the tropics to the subtropics, driven by eccentricity's amplification of precession. Consequently, the Holocene highstand at the lake was both larger and longer lived than the maximum highstand during the LIG.Annual layers were continuously deposited through the LIG in Lake Bosumtwi, and I also present a new, 12,100 year-long, varve record spanning the interval from 128.6 to 116.5 ka. Over the course of the LIG, lake level generally tracks sea surface temperatures (SST) in Gulf of Guinea, including an abrupt drop in lake level that lasted about 500 years ca. 118 ka, coincident with cool SSTs in the North Atlantic and severe aridity in Europe. I find that the despite the generally drier conditions, hydrology varied on similar timescales as the late Holocene, with pronounced multidecadal to centennial-scale variability with non-stationary periodicities. I also investigate the contribution of ocean thermal expansion to sea level rise during the LIG, using a synthesis of paleoceanographic data and a climate model simulation. Globally, LIG SSTs were similar to, or slightly cooler than late Holocene SSTs, with the exception of the North Atlantic, which was several degrees warmer. Consequently, thermal expansion was likely a minor component of sea level rise during the interval, explaining between -0.3 and 0.4 m. of the 6 to 8 m highstand. Lastly, I tested the potential of Raman spectroscopy as a new, non-destructive technique to rapidly measure oxygen isotopic ratios in carbonates at extremely high resolution. Analyses on a suite a synthetic calcites indicate that ¹⁸O/¹⁶O ratios can be measured directly from the Raman spectra and have a 1:1 correspondence with traditional mass-spectrometry measurements. At present, the technique does not have the precision necessary to record natural variability, although there is considerable potential for improving the precision of the technique.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectLast Interglacialen_US
dc.subjectSahelen_US
dc.subjectGeosciencesen_US
dc.subjectEemianen_US
dc.subjectIntertropical Convergence Zoneen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorOverpeck, Jonathan T.en_US
dc.contributor.committeememberCole, Juliaen_US
dc.contributor.committeememberCohen, Andrewen_US
dc.contributor.committeememberBrown, Eriken_US
dc.contributor.committeememberRussell, Joellenen_US
dc.contributor.committeememberOverpeck, Jonathan T.en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.