Session S27: Soft Matter Meets Climate Change

How does ice flow and crack in a warmingclimate?

One of the biggest uncertainties in sea-level rise projections results from our incomplete understanding of how surface melting of ice impacts the dynamics of ice sheets and ice shelves. As the atmosphere warms, surface meltwater impacts glaciers by changing the boundary conditions of both ice sheets (on top of solid bedrock) and ice shelves (floating over ocean). In this talk I will discuss (1) how meltwater triggers ice-shelf collapse through "hydrofracture", which caused the catastrophic disintegration of the Larsen B Ice Shelf, and (2) how meltwater lubricates the interface between ice sheets and bedrock. For the first half of the talk I will introduce a new approach combining 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 atmosphere warming. For the sencond half I discuss a new method combining theory with observations to understand the process governing the uplift of an elastic ice sheet caused by lake drainages, and reveal the seasonal changes of water lubrication between the ice sheet and bedrock.     

Ice mélange and the rheology of floating granular materials

Ice mélange is the Earth's largest granular material. Formed by broken icebergs created by glacial calving events in narrow straits or fjords, ice mélange can influence the dynamics of tidewater glaciers and thus the mass loss rate of surface ice into the oceans. Fundamentally, ice mélange is a floating granular material that jams as it is pushed through a frictional channel. Our scaled-down laboratory experiments examine its rheology, transverse velocity profiles, and thickness profiles. Using polypropylene (which has a density close to that of ice), we tested spheres, rectangular prisms, and collections of irregular shaped solids. We placed them in a narrow water tank with rough walls to simulate a fjord. The particles are slowly pushed by a "glacier terminus" composed of a suspended acrylic plate attached to force sensors. Using two cameras (one above and one on the side), we can calculate the surface velocity field using particle image velocimetry. The force on the terminus sharply increases when friction between particles and the tank walls causes the mélange to jam and buckle. Our preliminary results demonstrate that the force on a glacier terminus can vary by 10-50% between jamming events.   

Applying Complex Network Theory to Investigate the Fate of Creeping Landslides

Due to climate change and the resulting increase in heavy precipitation, hillsides are predicted to more frequently  transition from slow creep to catastrophic failure. While the pre-failure deformation is sometimes apparent in retrospect, it remains challenging to predict the sudden transition from gradual deformation to runaway acceleration. We apply methods developed to describe the physics of complex systems to investigate the spatiotemporal patterns of slow deformation at active landslides sites, including one that has recently undergone catastrophic failure. We transform measurements of the study sites, such as ground surface displacement, soil moisture, and topographic slope, into a spatially-embedded network in which the nodes are patches of ground and the edges that connect them. We focus primarily on weighting the edges using ground deformation time-series from satellite interferometric synthetic aperture radar (InSAR) data. To eliminate directional or geographical bias when sampling the area, we create a disordered mesh of nodes with Poisson sampling and use Delaunay triangulation to join nodes to their nearest neighbors. This spatially-embedded network is represented as a multilayer network where each layer represents a time slice captured from InSAR. We use community detection, which identifies strongly-correlated clusters of nodes, to identify patterns of instability. We test a variety of network metrics, such as the strength and flexibility of the communities, to quantify patterns of ground deformation leading up to failure. In our preliminary analysis, graphs of several such community metrics (e.g. consistent partitioning into communities, number of communities) show a quiescent period that ends in the weeks immediately prior to failure. These methods therefore show promise as a possible technique for highlighting regions at risk of catastrophic failure.   

Ice nucleation at negative pressures using molecular dynamics: Implications for atmospheric clouds

Mixed-phase clouds cover large portions of the planet and are highly relevant to the global climate, impacting the stability of the Arctic Ocean ice pack amongst other important climate systems. The evolution of these clouds is controlled by the process of ice nucleation in the supercooled cloud droplets. Modeling and accurate remote observation of these clouds is limited by an incomplete understanding of the physics governing the phase transition from liquid water to ice. Molecular Dynamics (MD) simulations of ice formation can help to reveal the fundamental mechanisms behind ice formation. I will briefly discuss experiments carried out at MTU that suggest a role for pressure fluctuations in nucleation. Then I will share results of evaluating homogeneous ice nucleation rates for the ML-mW and mW water models at negative pressures. Results indicate that the density difference between water and ice exhibited by these models plays a central role in controlling the change in nucleation rate. I identify an equation that provides a reasonable approximation for lines of constant nucleation rate, which can be useful in advancing the study of ice nucleation mechanisms.   

Charge Decay on Levitated Particles in Atmospheric Conditions

The transport of small atmospheric particles across the world's oceans is crucial for the global biome, for example, dust from the Sahara feeds the Amazon rain forest. This transport can be enhanced by electrostatic forces when individual particles are charged. Yet little is known about the lifetime of charge on such lofted particles. Laboratory measurements are challenging since particles must be levitated and manipulated without contact. Here we use an acoustic radiation trap to levitate and measure the net charge on isolated, millimetric particles for days. We examined particles with vastly different material properties: polystyrene, amaranth, pumice, and aerogel. The particles are charged with an ionizer, and we adjust the phase of the acoustic field to move the particle through a Faraday cup. In dry conditions, both positive and negative charge decay over 2-10 days. Increasing the humidity leads to large fluctuations in the half life, with the decay following nearly linear, logistic, or exponential behavior, with half lives as small as 0.1 days. Exposing polystyrene particles to UV radiation revealed a strong asymmetry in the electronic bound states: positively charged particles decayed in less than 1 hour, whereas negatively charged particles lasted for several hours.   

Effectively Reduce PM2.5 Air Pollution with Electrorheology

PM2.5 air pollution is an important and urgent issue for our environment. While there are many devices, including electric filter systems, widely used, all of them are unable to catch PM2.5 carbon particles effectively because these particles are very stable. On the other hand, PM 2.5 carbon particles are the most serious part of air pollution. They accelerate global warming and iceberg melting as well. We have developed a new technology with electrorheology, which can catch PM2.5 carbon particles effectively. Carbon particles are  stable. Under a strong electric field, they are polarized, but cannot be ionized. This is the main reason why they cannot be captured by the current electric filter systems. In our suystem, we first arrange to make the air flow specially turbulent, which has the carbon particles flowing near the flow boundary, where electrodes are located. Then under strong electro-rheological interaction, these carbon particles are aggregated on the electrodes. In short, they are caught by the electrodes. Our lab tests have confirmed that this technology can catch more than 90% PM2.5 particles in air. Especially, it can catch carbon particles very effectively. We hope that this technology can effectively reduce PM2.5 air pollution and global warming..   

    

Upgrading Low-Carbon Pathways for Cement Production in the United States

The emissions intensity for cement production in the United States is ~20-30% higher than in the European Union, India, and China. When comparing the United States to these other countries in terms of the green cement technologies implemented, it becomes apparent that there is considerable scope domestically to reduce emissions from the cement sector. In cement production, over 50% of the CO₂ emissions are caused by inherent material processes due to calcination. The composition of cement and its different formulations using industrial wastes and natural materials have a major role to play in lowering emissions. We will discuss material options and readily available technology solutions for decarbonizing cement production which can be incentivized by policy changes in the near term. By adopting key technological advances in clinker substitution and energy efficiency, we estimate an annual carbon mitigation potential of up to 38% for United States' cement production. Starting from this analysis, we will discuss how a range of climate policy levers such as standards, procurement policies, and sectoral agreements, can be implemented to upgrade low-carbon cement technologies and bring the United States cement sector on par with the rest of the world in terms of sustainability.   

Upcycling plastic sheets by scrolling yarns guided by Schläffli origami

We discuss a new tensional twist-folding framework for hyperelastic sheets leading to re-deployable yarns with intricate crossectional structures. Our experiments demonstrate that applied tension drives the folding of stretchable sheets as opposed to traditional compression-induced folding methods in origami with bendable sheets, generating new fabrication strategies. Using microfocus x-ray imaging, we show that tensional twist-folding is surprisingly ordered and can be used to transform thin elastic sheets into delicate nested multilayered structures. We find spiral accordion folded sheets can be algorithmically generated using rigid origami kinematics represented by Schläfli symbols. We uncover the key role of the sheet geometry and elasticity to set the fold number and organize the folding into tightly scrolled yarns. Further, guided by the twisting of two filaments into a rope, we develop a geometric yarn model to explain the growth of yarns with twist. Because of the great control of the internal yarn structure, tensional twist-folded offers a promising avenue for waste upcycling and functional yarns with optimized mechanical strength and energy storage capacity.   

Characterization of a novel gel material for oil-spill remediation

Oil spills. It is therefore critical that we are able to quickly and efficiently mobilize remediation efforts to minimize the negative impact to the surrounding in environment. This presents unique challenges for containment and cleanup when the spill occurs on open water due to the dynamic nature of the aquatic environment.  Historically, these spills have had drastic consequences and there is a clear need for more effective approaches to deal with them. In this presentation we describe and characterize a novel material that appears to form a gel in either oil or water at low concentrations. In both cases, the gel is formed upon cooling after heating to dissolve the material. The aqueous gel that is formed is then shown to behave as an absorbent material capable of absorbing approximately 100 times its mass in oil. In this work we investigate how the compression strength and rate of oil absorption depend on the concentration of the material and the presence of surfactants in the aqueous phase used to form the gel.   

Simulating supercritical carbon dioxide flow and trapping in microscopic rock pore networks

Carbon dioxide geological storage has the potential to reduce the atmospheric carbon dioxide concentration and limit climate change. In this method, carbon dioxide is injected into underground geological formations to permanently reside in the capillary networks of reservoir rocks. Due to the physical mechanism of capillary trapping, carbon dioxide is immobilized inside the rock's pore channels. We deploy computational models that describe a rock's pore space as a network of connected capillaries with spatially varying radii in which fluids flow in the laminar regime. The network-based representation is extracted from x-ray microtomography images of representative rock samples, providing the geometric boundaries for single- and multi-phase flow simulations. In this contribution, we map the parameter space by assessing the effects of fluid properties such as viscosity, interfacial tension and contact angle on the amount of carbon dioxide that can be trapped inside the capillary network. In order to decrease the computational cost, we employ a novel network simplification technique that preserves the original network's geometrical and topological properties. We demonstrate how the choice of parameters determines the trapping efficiency of supercritical carbon dioxide in digital representations of sandstone rock samples at elevated pressures and temperatures.