Date of Award

5-2013

Level of Access

Campus-Only Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

Advisor

Andrei V. Kurbatov

Second Committee Member

Nancy A.N. Bertler

Third Committee Member

Gordon S. Hamilton

Abstract

The ice flow, stable water isotopic composition, and glaciochemistry of ice within the Allan Hills Blue Ice Area (AH BIA), Antarctica, is investigated to determine its potential for contributing to and extending the currently available 800 ka ice core record of paleoclimate. The investigation began with a study of ice dynamics within the AH BIA. The horizontal (u) and vertical (ż) ice velocities, determined using high-precision GPS measurements, are 1.5 to 50 (±0.12) cm a-1 and 2-3 (±0.50) cm a-1, respectively. The significant positive z and low u verify that old ice is present at the surface. Surface topography, in combination with u, was used to delineate a flowline (A-B) along which ice of continuous age was collected for the next stage of the investigation. Surface ice was recovered along 5 km of A-B and a 225 meter core was drilled at its midpoint. Ice samples were analyzed for stable isotopes of water (δD, δ18O), which are common proxies for temperature. The resulting profiles exhibit variability consistent with the magnitude of glacial-interglacial transitions in East Antarctica. These variations, in combination with 40Aratm and δ18Oatm constrain the age of sampled ice to 90-250 ka. However, the 100 meters of directly above bedrock was not collected and the bottom depth is calculated to be at least 400 ka. The final phase of the investigation involved determining the concentrations of terrestrial and marine chemical species in ice from multiple points along A-B. Concentrations ranged from pg L-1 level for rare earth elements to μg L-1 level for multi-sourced compounds like sulfate. The concentrations of all analytes were anticorrelated with stable water isotope values indicating they had preserved a record of changes in atmospheric circulation, source strength, and continental aridity. The composition of rare earth elements points to Australia as an important interglacial dust source, while molar ratios of major ions, particularly Ca2+:Cl- and Mg2+:Cl-, suggest that transport pathways through the McMurdo Dry Valleys cannot be disregarded. In summary, the data collected suggest that ice within the AH BIA is stratigraphically conformable, is older than that recovered in surrounding regions and does contain a well-preserved environmental record.

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