(In)stability of glaciers and climate in volcanic landscapes of the Thwaites Glacier, Antarctica, and American Pacific Northwest

This studentship will develop new dating tools using cosmogenic isotopes and, in turn, apply them in two volcanic landscapes (Antarctica and Pacific Northwest, USA) to solve important and societally relevant problems concerning past and future changes to glaciers in a warming world.

First, this student would join the NERC-NSF International Thwaites Glacier Collaboration, ITGC, which is a joint UK-US $25M research program aiming to significantly improve our understanding of the future evolution of the massive Thwaites Glacier in West Antarctica and its likely contribution to sea level change in the coming decades and centuries. The project will investigate past glacier changes of the Thwaites Glacier using state-of-the-art geochemical methods on rock samples collected from volcanic peaks next to and under major ice streams. Objectives are to: 1) develop new geochemical dating tools using cosmogenic radionuclides (e.g., Be-10) in mafic minerals, and 2) to determine the timing and duration of past fluctuations in ice thickness over several millennia, which will be investigated using measurements of subglacial bedrock cores drilled during the parent project, "Geological History Constraints (GHC)".

Second, as the American Pacific Northwest relies heavily on the snowpack in the High Cascades as a water resource, this studentship will determine the age of prehistoric (pre-1900) extents of three Pacific Northwest glaciers, using cosmogenic (traditional He-3, Cl-36, and newly developed Be-10) surface exposure ages on moraines composed of volcanic rocks of the Cascades. These ages will determine precedence for retreat of the glaciers over the last century because such retreat reflects an overall negative mass balance due to reduced snowpack at the end of the summer, which will, in turn, provide context for recent declines in end-of-summer snowpack. The age data will then be implemented in glacier model simulations. Results will provide a late-Holocene view on how unprecedented current glacier retreat is, and consequently a century-scale test of primacy for Cascade snowpack decline. Age data will establish a north-south transect of western North American prehistoric glacier changes to complement other proxy records, which will test hypotheses on centennial-scale patterns in western North American late-Holocene hydroclimate change. Results will provide a novel target for testing regional climate and glacier models that are necessary for accurate future projections of snowpack and glacier changes.

The student will conduct field work in the Pacific Northwest (USA), develop methods and prepare samples for cosmogenic isotope surface exposure dating in the CosmIC laboratory at Imperial College London, and conduct measurements by accelerator mass spectrometry (AMS) at ANSTO (Australia). This is a multidisciplinary project, with significant training in field, laboratory, and analytical methods. A passion for science that matters to society is critical.