Geochemical characterization of shallow sediments from the grounding zone of the Whillans Ice Stream

Abstract

The research presented in this thesis focused on subglacial flow beneath the West Antarctic Ice Sheet (WAIS) and its potential influence near the grounding zone. Antarctic grounding zones are of specific scientific interest because they can impact the stability of the continental ice sheet and its breakup, potentially resulting in significant sea level rise. My major objective was to determine whether there was influence of subglacial water at the Whillans Grounding Zone (WGZ) on the Siple Coast of the WAIS. A gravity corer was used to collect a 70 cm sediment core through 780 m of ice borehole drilled using a hot water clean access drilling system. The core was collected in a marine embayment adjacent to the WGZ beneath a 10 m water column. I used a combination of geochemical, isotopic and organic matter analyses to characterize the benthic sediments, porewater and water column. The geochemical and isotopic data showed the influence of subglacial freshwater on sediment porewater at specific depths in the 70 cm core. Vertical gradients of chloride and sulfate between surficial sediment and the overlying water column indicated ion diffusion from porewater to the column water. Dissolved organic matter concentration of sediment porewater and the overlying water column also indicated upward diffusion occurs from porewater to the overlying seawater. Sediment particulate carbon and nitrogen data showed that benthic sediments were more depleted in nitrogen than the overlying seawater. Sediment particulate carbon and nitrogen data showed that benthic sediments were more depleted in nitrogen than the overlying seawater. Geochemical, isotopic and organic matter data supports the influence of subglacial freshwater at the WGZ.