Team Members

Columbia University
Dr. Haim Waisman

University of Michigan
Dr. Jeremy Bassis

Vanderbilt University
Dr. Ravindra Duddu

Global Warming Footprint

NSF Program Manager
Dr. Paul Cutler

The funding support provided by the National Science Foundation, Polar Programs division, Grant # PLR‐1341472.

Summary

 

 

This project seeks to advance our ability to predict the fate of the Greenland and Antarctic ice sheets and to quantify the ice sheet contribution to sea level rise in the coming centuries. Accomplishing this requires that we have a better understanding of why icebergs that can exceed the size of small New England States, detach and drift away from ice shelves. Iceberg calving accounts for nearly 50% of the mass lost from ice shelves, it plays an important role in the mass balance of glaciers and ice sheets, but remains a poorly understood process.

The model presented in this project can simulate both the flow and fracture of glacier ice, (including the slow creeping of that ice) as it spreads under its own weight all the way to the complete failure and detachment (calving) of icebergs from glaciers and ice shelves (floating expanses of glacier ice).Iceberg calving is also not yet accounted for in the current generation of continental-scale ice sheet models, which are used in state-of-the-art climate simulations and sea level rise projections, because simulating iceberg calving requires that we understand the initiation and propagation of fractures within the ice over timescales that can range from a few seconds to decades or even centuries.

To address this problem, the primary objective of this project is to address this gap in our understanding by translating physical and computational approaches originally developed to simulate the fracture of quasi-brittle materials, like metals and concrete, to the fracture of glacier ice. Since it is both impossible and impractical to simulate the propagation of each individual crack in an ice sheet, we developed a "continuum damage mechanics" approach that handles collections of cracks in a physically and thermodynamically consistent way to simulate failure at the large scale. This is accomplished by using an approach that can simulate what happens to fractures after they form at the interface with the ocean.

Link to Dr. Ravindra Duddu's Collaborative Ice Project

Project Publications

Papers

1. J. Londono, L. Berger-Vergiat and H. Waisman, An equivalent stress-gradient regularization model for coupled damage-viscoelasticity, Computer Methods in Applied Mechanics and Engineering, Accepted April 2017. (link)
2. M. Mobasher, R. Duddu, J. Bassis and H. Waisman, Modeling hydraulic fracture of glaciers using continuum damage mechanics, Journal of Glaciology, 62(234):794-804, 2016.(link)
3. J. Londono, L. Berger-Vergiat and H. Waisman, A Prony-series type viscoelastic solid coupled with a continuum damage law for polar ice modeling, Mechanics of Materials, 98:81-97, 2016.(link)
4. M. Mobasher, L. Berger-Vergiat and H. Waisman, Non-local formulation for transport and damage in porous media, Computer Methods in Applied Mechanics and Engineering, 324:654-688, 2017.(link)

Presntations

1. J. Londono, L. Berger-Vergiat and H. Waisman, An equivalent stress-gradient regularization model for coupled damage-viscoelasticity, Computer Methods in Applied Mechanics and Engineering, EMI 2016 Conference, Vanderbilt University. (link)
2. M. Mobasher, R. Duddu, J. Bassis and H. Waisman, Modeling hydraulic fracture of glaciers using continuum damage mechanics, EMI 2016 Conference, Vanderbilt University.(link)
3. J. Londono, L. Berger-Vergiat and H. Waisman, A Prony-series type viscoelastic solid coupled with a continuum damage law for polar ice modeling, EMI 2014 Conference, McMaster University, Canada. (link)

Sample Project Results

The following are two examples of studies performed in this project. The input and output files can be downloaded by clicking on the link in the title of each example. Each simulation folder has the following files:

Input file starting with letter "I"

Log file starting with letter "L"

Output file starting with letter "O"

Results .vtu files that can be viewed using any of the popular visualization software packages e.g. Paraview

All input and output files have the FEAP format.

 

• Simulation of water-filled crevasses

The attached files are a sample of the simulations of water-filled crevasses propagations. The cases of hw/H=0.25 and hw/H=0.8 are included for:1) dry surface crevasses and wet basal crevasses, and 2) wet surface and basal crevasses. The following figures are taken from Mobasher et. al (2016) refrenced in the list above.

 

Figure 1: Simulations of dry surface crevasse and wet basal crevasse Figure 2: Simulations of wet surface and basal crevasse Figure 3: Temporal evolution of the wet surface and basal crevasses for hw/H=0.25
• Ice strain-rate example

An idealized grounded ice slab subjected to a constant strain rate of 0.005 (1/s) is used to study glacier crevasse propagation. The slab has dimensions of H = 250m and L = 500m and the initial crevasse depth 10 m, and width 10 m, is assumed to be dry at the top surface.

Figure 4: Strain rate example schematic

 

Comparing the local and nonlocal damage models for two different sets of mesh sizes (fine and coarse) the proposed model display consistent crevasse depth and rate of propagation when the nonlocal model is used.

Figure 5: Damage contours from local vs. non-local models for different mesh sizes

 

Superior performance of the nonlocal model is also confirmed when comparing the average mean stress-strain results across the center of the ice slab. Mesh sensitive results are clearly observed in the local model.

Figure 6: Volumetric stress vs. strain for different models