Publication Date

2012-12-10

Availability

Embargoed

Embargo Period

2014-12-10

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine Geology and Geophysics (Marine)

Date of Defense

2012-11-14

First Committee Member

Larry C. Peterson

Second Committee Member

Peter K. Swart

Third Committee Member

Ali Pourmand

Fourth Committee Member

Robert C. Thunell

Abstract

It is becoming increasingly apparent that rapid climate change on suborbital timescales is a persistent feature of Pleistocene climate. The rapid climate changes of the last glacial period – Dansgaard-Oeschger (D/O) cycles and Heinrich Events (HEs) – involved changes in sea and air temperature, atmospheric and oceanic circulation, and changes in hydrologic patterns that were nearly global in nature. Counterparts to D/O cycles and HEs have been found in marine sediment records of early glacial periods as far back as ~2.5 mya. Although the millennial-scale climate events of the last glacial period have been well studied, there is still much that is not understood about suborbital climate change, including its occurrence in glacial versus interglacial periods, the involvement of the tropics in abrupt climate change, and the actual trigger for these rapid, millennial-scale events. This dissertation utilizes a nearly 600,000-year long, high-resolution record of paleoclimate and paleoenvironmental change from the Cariaco Basin, Venezuela, in order to examine the patterns of millennial climate change in the tropics prior to the last glacial-interglacial period. First, a multi-proxy approach is used to examine the last deglaciation in order to establish as rigorously as possible the response of the Cariaco Basin to the multitude of changes that accompany the transition from a glacial to interglacial period. Based on relationships established between the Cariaco proxy records and climate and environmental forcing mechanisms, the full 600,000 years of available sediment sequence is explored for the patterns and distribution of millennial scale variability, using high resolution Scanning X-Ray Fluorescence records. The results of this dissertation show that suborbital scale climate variability occurred throughout the past 600,000 years in the tropics. Changes in biogenic opal flux in the Cariaco Basin are linked to changes in oceanic circulation, and appear to occur during periods of ice rafting in the Northern Hemisphere. Changes in proxies for the tropical hydrologic cycle reveal that interstadial-like periods of warmth were a common feature of glacial periods as far back as MIS 14; however, a proxy for bottom water anoxia reveals that suborbital scale variability is not restricted to glacial periods but occurred as well during the last three interglacial periods when continental ice volume was reduced. In light of this latter finding, an active role for the tropics in triggering suborbital scale climate change is proposed. The complicated nature of deglacial climate change, as evidenced by results from the multi-proxy study of the last deglaciation also indicate that local forcings and feedbacks are also important in the tropics during periods of rapid climate change. A supplemental file can be found at http://scholarlyrepository.miami.edu/oa_dissertations/916

Keywords

tropical paloeclimate; rapid climate change; sediment geochemistry; stable isotope and Mg/Ca analysis

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