2024-2025
Changing ice in a warming climate: a data-driven approach
One of the greatest uncertainties in sea-level rise projections arises from our incomplete understanding of how ice sheets would lose mass in a warming climate. In this talk, I will discuss two poorly understood aspects of ice dynamics. The first concerns how the melting of ice surfaces triggers ice-shelf collapse through hydrofracture, which caused the catastrophic disintegration of the Larsen B Ice Shelf. I will introduce a new approach that combines physics-based models and deep learning techniques to provide physical insights into the stability of ice fractures and predict the vulnerability of Antarctic ice shelves to atmospheric warming. In the second part of the talk, I will discuss the complex rheology of Antarctic Ice Shelves. The flow law of ice, i.e., ice rheology, directly governs the dynamics of ice shelves but is challenging to measure in the field. Here, with physics-informed deep learning and remote-sensing observations, we identify flow laws that differ from those previously assumed in ice-sheet models. Our results suggest the need to reassess the impact of ice flow laws on the future projection of sea-level rise.
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Geodynamics of early crust formation: Constraints on Earth’s long-term tectonic and thermal evolution
A unique feature of the Earth compared to the other rocky planets of our solar system is the operation of plate tectonics at the present day. However, how and when Earth developed into this present-day state is unclear. Key to deciphering Earth’s long-term tectonic evolution is the growth of the first continents, as these represent the oldest extant rock record providing our best window into the geodynamic processes of the very early Earth. Geochemical observations have been used to argue for a switch in the mode of crust formation at ~3.8-3.6 Ga, from continent formation via melting at the base of a thick, volcanically active oceanic crustal pile, to continent formation by some form of subduction. I use numerical models of early Earth mantle convection and crust formation, combined with the key geochemical observations, to provide new constraints on such a scenario. I show that continent formation by slab melting during subduction can only occur when subduction is sluggish and present a new mechanism for such subduction on the early Earth. I further show how continent formation by ocean plateau melting >~3.6 Ga is plausible, but with strict limits on the rates of volcanism in such a system that have important implications for mantle heat loss. I discuss how both sets of models together provide a possible scenario for the tectonic and thermal evolution of the early Earth.
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