The role of meltwater in reshaping the structures of icy porous media
Xiaojing (Ruby) Fu, Assistant Professor of Mechanical and Civil Engineering at California Institute of Technology.
Abstract: Icy porous materials such as snow or firn are ubiquitous in both Earth and planetary settings. Their microstructures (e.g., porosity) play an important role in dictating the reflectivity, fluid storage capacity, thermal conductivity, and mechanical properties of the larger-scale systems. Thus, understanding the complex physics that control the microstructure evolution of icy porous media is an important component in creating robust predictions of Earth’s cryosphere in response to climate warming, and in devising engineering strategies for the exploration of icy moons in our solar system. While it is well known that gravity-driven compaction leads to densification of the pore structure over depth, less is known about the role of meltwater in reshaping the structures of icy porous media across scales.
In this talk, I will describe our recent efforts in understanding how the movement of liquid water through porous ice reshapes its porosity structure via flow instability and phase transitions of water. I will first discuss the pore-scale problem and present a phase-field model that simultaneously captures the phase transitions of water amongst its liquid, solid and vapor phases. With this model, we show that the presence of quiescent meltwater films can accelerate the microstructural coarsening of porous snow during the process of metamorphism. Next, I will describe a Darcy-scale model that demonstrates how melt refreezing coupled with unstable infiltration reshapes the porosity structure of snow and leads to the formation of ice pipes and ice lenses commonly observed in the field. I will conclude by discussing the implications of these new physical insights for large-scale meltwater transport and hydrological processes in snow and glacial systems.
About: Xiaojing (Ruby) Fu is an Assistant Professor of Mechanical and Civil Engineering at California Institute of Technology. She received her BS in Applied Mathematics from Clarkson University, a MS in Computational Engineering, and a PhD in Civil & Environmental Engineering from MIT. She is awarded the Miller Postdoctoral Fellowship at UC Berkeley in 2018, hosted by the Earth & Planetary Science department. She joined Caltech in 2021 and leads the Mechanics of Porous Media Flow group. Her group studies the physics of multiphase fluid mechanics through porous media and how it shapes our natural and engineered environments, using theory, modeling, and laboratory experiments.