A geologic approach to resolving critical uncertainties in the impact of geomagnetic variance on in-situ cosmogenic nuclide production

Objectif

Accurate prediction of future climate impacts hinges upon the robust reconstruction of past climate change. Palaeoclimate records serve as benchmark data for modern climate models and are a key element of model validation. Glaciers in particular are sensitive indicators of climate, providing geologic records of past climate fluctuations in the form of moraines. Recent advances in cosmogenic nuclide (CN) surface-exposure dating now allow these landforms to be dated directly, opening glacial geology as a potentially rich global archive of past climate change. However, fundamental limitations in our ability to exploit glacial records as a climate proxy are uncertainty in the 1) variance of CN production rates over time and 2) validity of numerical frameworks used to account for potential production rate variation. I propose to address these challenges directly by developing CN production rates for multiple periods from a single region in the tropics, where the theoretical impact of production rate variability is greatest. I will work with geochronologist Dr. Gordon Bromley of the host institution, National University of Ireland, Galway, to implement my field-based campaign in the Peruvian Andes, where I will map and sample volcanic deposits for CN calibration. I will be trained in noble gas mass spectrometry by Dr. Pierre-Henri Blard at partner institution Centre de Recherches Pétrographiques et Géochemiques, France. My ultimate fellowship goal is to refine and strengthen the surface-exposure dating technique in order to open the glacial geologic record as a global proxy for past change. Crucially, the results of my proposed research will provide both myself and the wider scientific community with the cutting-edge toolset required to apply cosmogenic nuclides to deposits of varying age and location and to quantify the impact of past – and future – climate change.