OPP-PRF: Investigating the Geophysical Signatures of Partial Melt in Deforming Icy Systems

Glacial mass loss, a key indicator of climate change, is governed by the flow of ice. Glaciers lose mass to the sea due to internal ice movement, or ‘flow,’ caused by gravity. The rate of flow expected, which is described by a mathematical relationship based on laboratory observations of solid ice, is a large source of uncertainty in models of sea level rise. Ice flow laws do not yet incorporate the role of meltwater, even though water ice often occurs close to its melting temperature. Our models of increasingly warm ice therefore do not fully capture the enhanced flow rates that are known to occur when meltwater is present, and thus do not always match natural observations. This work hypothesizes that the orientation of the meltwater itself is key to understanding flow, drawing parallels from recent experimental work on rock-magma systems, and aims to create new flow laws that explicitly include meltwater via the results of new experimental deformation tests. The investigator will use the results of these tests to improve existing deformation simulation software so that future climate scientists can extrapolate specific laboratory results to other settings. As icy settings warm due to climate change, the role of meltwater in controlling glacial flow will only increase. The ice flow laws established from this work will provide necessary, timely inputs for models of iceberg calving and sea level rise, yielding direct benefit to society through improved understanding of natural hazards threatening our planet. The investigator will also train an undergraduate student and advance the involvement of women and gender minorities in STEM research through in-person outreach activities.To characterize and quantify the role of meltwater orientations in governing the geophysical properties of deforming icy systems, this project will employ multiple experimental geometries: compression, torsion, and a combination of the two. Several compressive deformation tests will also include forced oscillations, increasing our understanding of temperate ice flow in tidally modulated settings. These experiments will allow researchers to examine how both meltwater and solid ice orientations evolve in diverse glacial settings, using unique cryogenic imaging machinery; this microstructural imaging will then be combined with mechanical data from deformation experiments to create flow laws for temperate ice that contain a specific term for the evolving role of meltwater. The results of all experiments will then be used to modify open-source microstructural deformation simulation models, yielding publicly accessible computational tools that reflect the physics of melt orientation. This project will thus produce a flow law and microphysical models that clarify how ice and meltwater together create the macroscopic geophysical properties of deforming ice across regimes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.