Publication Date

April 2015

Advisor(s)

Suzanne O'Connell

Major

Earth and Environmental Sciences

Language

English (United States)

Abstract

Anthropogenic climate change poses great challenges and existential questions to humankind. Communities must be made resilient to the inevitable destructive effects that we are sure to see in the coming decades, and our interactions with the complex, interconnected ecosystems in which we participate need to be restructured in hopes of mitigating continued adverse consequences. The Pliocene epoch is, in many ways, a climatic analogue to our current world. Atmospheric CO2 levels exceeded 400 ppm during the mid-Pliocene warm period (Haywood et al., 2009), a level that was surpassed in May of 2013 (Blunden, 2014). Therefore, the epoch can shed light on the consequences of current climate change. The Pleistocene epoch, following the Pliocene epoch, is characterized by cycles of Antarctic and Northern Hemispheric glaciation (Pollard and DeConto, 2009), thereby providing important information on the factors necessary in inducing and reducing polar glacial conditions. The stability of the East Antarctic Ice Sheet (EAIS) is now an area of study experiencing much contention and is one of the focal points of this study. Holding ~26.5 million km3 of ice, the EAIS has the potential to raise global sea levels tens of meter (Gross, 2014). While previously thought to have remained stable during the Pliocene and Pleistocene epochs, it now seems conceivable that the EAIS coastline experienced significant glacial retreat throughout the late Pliocene as well as the early Pleistocene (Raymo et al., 2006, Cook et al., 2013). Understanding the mechanisms involved in creating the stability of Antarctic ice sheets during these epochs will allow us to more properly estimate the level of deglaciation that we can expect to see as a result of anthropogenic climate change. This will aid in estimating the magnitude of sea level rise that the world will experience, thereby providing coastal communities with information to prepare appropriately. Using X-ray fluorescence data from deep-sea sediment cores recovered from the Weddell Sea off the coast of the EAIS (in conjunction with diffuse spectral reflectance and magnetic susceptibility data from the same cores), this study focuses on identifying the roles that Milankovitch cycles had and continue to have on Antarctic climate via the statistical techniques known as Varimax-rotated principal component analysis and wavelet analysis. 100 kyr eccentricity, 41 kyr obliquity, and ~20 kyr precession were identified as the dominant Milankovitch cycles at the time of deposition of Core 8R during the Pliocene, and 400 kyr eccentricity and 100 kyr eccentricity were identified as the dominant Milankovitch cycles at the time of deposition of Core 2R during the Pleistocene. By identifying and applying these Milankovitch cycles to the periodicities obtained from the wavelet spectra, sedimentation rates of 6.58 cm/kyr for Core 8R and ~1.44 cm/kyr for Core 2R were derived.

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