Vegetation and Climate of the African Tropics for the Last 500,000 Years

Persistent Link:
http://hdl.handle.net/10150/293752
Title:
Vegetation and Climate of the African Tropics for the Last 500,000 Years
Author:
Ivory, Sarah Jean
Issue Date:
2013
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 29-Apr-2014
Abstract:
In the last few decades, we have been witness to unprecedented changes in precipitation and temperature. Such alterations to our climate system have important implications for terrestrial ecosystems that billions of people depend on for their livelihood. The situation is especially tenuous for those living directly off the landscape via resources from natural ecosystems or subsistence agriculture as in much of tropical Africa. Studies of past climates provide potential analogues and help validate models essential for elucidating mechanisms that link changes in climate mean and variability and how they may affect ecosystem distribution and productivity. However, despite the importance of the paleo-record for insight into the future, tropical proxy records are rare, low resolution, and too short to capture important intervals that may act as analogs, such as the Last Interglacial (MIS 5e; ~130-115ka).Long, high-resolution drill cores from Lake Malawi, southeast Africa, provide a record of tropical climate and vegetation that extends back ~1.2mya, comprising many continuous glacial-interglacial cycles. My primary research involves conducting pollen analyses on these cores. First, I analyzed a high-resolution interval of the shortest Malawi core in order to better understand abrupt vegetation transitions during the Last Deglaciation. Further analysis was conducted on the longest Malawi core, beginning with an interval covering all of the Penultimate Glacial through the Last Interglacial. The resultant pollen data has shown that abrupt, large-scale landscape transitions from forest to desert follow local insolation and lake levels at the site, with a strong dependence of forest/woodland vegetation types on mean rainfall as well as rainfall seasonality. The interpretation of paleodata requires a good understanding of modern processes, thus another project has focused on using model simulations of the Last Interglacial and modern satellite NDVI time series to highlight dynamical and statistical relationships between vegetation and climate change. This work suggests that despite suggested links between monsoon intensity and SSTs in the southern African tropics, insolation controls on atmospheric circulation are the primary drivers of vegetation reorganization. In addition, this work highlights the importance of rainfall seasonality and dry season length in addition to precipitation controls on vegetation.
Type:
text; Electronic Dissertation
Keywords:
climate dynamics; global change; Malawi; Quaternary; tropical vegetation; Geosciences; Africa
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Geosciences
Degree Grantor:
University of Arizona
Advisor:
Cohen, Andrew S.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleVegetation and Climate of the African Tropics for the Last 500,000 Yearsen_US
dc.creatorIvory, Sarah Jeanen_US
dc.contributor.authorIvory, Sarah Jeanen_US
dc.date.issued2013-
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 29-Apr-2014en_US
dc.description.abstractIn the last few decades, we have been witness to unprecedented changes in precipitation and temperature. Such alterations to our climate system have important implications for terrestrial ecosystems that billions of people depend on for their livelihood. The situation is especially tenuous for those living directly off the landscape via resources from natural ecosystems or subsistence agriculture as in much of tropical Africa. Studies of past climates provide potential analogues and help validate models essential for elucidating mechanisms that link changes in climate mean and variability and how they may affect ecosystem distribution and productivity. However, despite the importance of the paleo-record for insight into the future, tropical proxy records are rare, low resolution, and too short to capture important intervals that may act as analogs, such as the Last Interglacial (MIS 5e; ~130-115ka).Long, high-resolution drill cores from Lake Malawi, southeast Africa, provide a record of tropical climate and vegetation that extends back ~1.2mya, comprising many continuous glacial-interglacial cycles. My primary research involves conducting pollen analyses on these cores. First, I analyzed a high-resolution interval of the shortest Malawi core in order to better understand abrupt vegetation transitions during the Last Deglaciation. Further analysis was conducted on the longest Malawi core, beginning with an interval covering all of the Penultimate Glacial through the Last Interglacial. The resultant pollen data has shown that abrupt, large-scale landscape transitions from forest to desert follow local insolation and lake levels at the site, with a strong dependence of forest/woodland vegetation types on mean rainfall as well as rainfall seasonality. The interpretation of paleodata requires a good understanding of modern processes, thus another project has focused on using model simulations of the Last Interglacial and modern satellite NDVI time series to highlight dynamical and statistical relationships between vegetation and climate change. This work suggests that despite suggested links between monsoon intensity and SSTs in the southern African tropics, insolation controls on atmospheric circulation are the primary drivers of vegetation reorganization. In addition, this work highlights the importance of rainfall seasonality and dry season length in addition to precipitation controls on vegetation.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectclimate dynamicsen_US
dc.subjectglobal changeen_US
dc.subjectMalawien_US
dc.subjectQuaternaryen_US
dc.subjecttropical vegetationen_US
dc.subjectGeosciencesen_US
dc.subjectAfricaen_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.advisorCohen, Andrew S.en_US
dc.contributor.committeememberLézine, Anne-Marieen_US
dc.contributor.committeememberJackson, Stephenen_US
dc.contributor.committeememberRussell, Joellenen_US
dc.contributor.committeememberDavis, Owenen_US
dc.contributor.committeememberCohen, Andrew S.en_US
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