UC San Diego

Mineral dust preserved within Antarctic ice is a sensitive and versatile tracer of past climate. The concentration, composition, and size distribution of dust delivered to Antarctica reflect changes in the climatic conditions that control its production, mobilization, and transport. This dissertation explores how these physical and geochemical properties of dust can be decoded to reconstruct changes in atmospheric circulation, evaluate post-depositional processes, and constrain the relative age of ice in East Antarctica. This research focuses on two, high-volume ice cores drilled at the Allan Hills Blue Ice Area, which is known for its unique accessibility to exceptionally old ice. In Chapter 1, we examine dust from a stratigraphically ordered section of ice spanning 145-120 ka, which captures the deglacial transition from Marine Isotope Stage (MIS) 6 to MIS 5e. Through the analysis of Sr-Nd isotope compositions, particle size distributions, rare earth elemental concentrations, and scanning electron imagery, we show a key provenance shift. MIS 6 dust is predominantly sourced from South America, whereas MIS 5e dust is derived from a heterogeneous Antarctic mixture consisting of volcanic rock material of the West Antarctic Rift System and exposed outcrops of the Transantarctic Mountains. When compared with Earth System model simulations, the dust record supports a scenario involving the loss of the Ross Ice Shelf and/or diminished West Antarctic Ice Sheet. In Chapter 2, we expand and extend the dust provenance record to ice spanning 800-500 ka and >1250 ka. During the younger 800-500 ka interval, ice tilting/thinning results in time-averaging of glacial and interglacial dust sources. However, in the deepest/oldest samples >1250 ka, Sr-Nd isotope compositions and particle size data suggest overprinting by subglacial interactions, which complicates provenance interpretations. In Chapter 3, we assess the utility of uranium-series isotopes as a stratigraphic tool applied to ice from the 800-500 ka interval. We show that 234U/238U activity ratios in ice offers a promising approach for relative dating, but the technique faces challenges for absolute age determination. Together, this dissertation demonstrates multiple, complementary ways in which the analysis of dust can be used to probe variability in atmospheric transport, stratigraphy, and chronology in Antarctic ice.