The response of fabric variations to simple shear and migration recrystallization

Kennedy, Joseph H.; Pettit, Erin C.

doi:10.3189/2015JoG14J156

Title: The response of fabric variations to simple shear and migration recrystallization

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Abstract

The observable microstructures in ice are the result of many dynamic and competing processes. These processes are influenced by climate variables in the firn. Layers deposited in different climate regimes may show variations in fabric which can persist deep into the ice sheet; fabric may 'remember' these past climate regimes. In this paper, we model the evolution of fabric variations below the firn–ice transition and show that the addition of shear to compressive-stress regimes preserves the modeled fabric variations longer than compression-only regimes, because shear drives a positive feedback between crystal rotation and deformation. Even without shear, the modeled ice retains memory of the fabric variation for ~200 ka in typical polar ice-sheet conditions. Our model shows that temperature affects how long the fabric variation is preserved, but only affects the strain-integrated fabric evolution profile when comparing results straddling the thermal-activation-energy threshold (~–10°C). Even at high temperatures, migration recrystallization does not eliminate the modeled fabric's memory under most conditions. High levels of nearest-neighbor interactions will, however, eliminate the modeled fabric's memory more quickly than low levels of nearest-neighbor interactions. Finally, our model predicts that fabrics will retain memory of past climatic variations when subject to a wide variety of conditionsmore » found in polar ice sheets.« less

Authors:

Kennedy, Joseph H. ^[1]; Pettit, Erin C. ^[2]

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Computational Earth Sciences Group; Univ. of Alaska, Fairbanks, AK (United States). Dept. of Physics
Univ. of Alaska, Fairbanks, AK (United States). Dept. of Geosciences

Publication Date:: Mon Jun 01 00:00:00 EDT 2015

Research Org.:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Alaska, Fairbanks, AK (United States)

Sponsoring Org.:: National Science Foundation (NSF)

OSTI Identifier:: 1187919

Grant/Contract Number:: OPP#0948247; OPP#0940650; OPP#0636795

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Glaciology

Additional Journal Information:: Journal Volume: 61; Journal Issue: 227; Journal ID: ISSN 0022-1430

Publisher:: International Glaciological Society

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; anisotropic ice; glacial rheology; ice crystal studies; ice rheology; recrystallization

Citation Formats


                    Kennedy, Joseph H., and Pettit, Erin C. The response of fabric variations to simple shear and migration recrystallization.  United States: N. p., 2015. 
Web.  doi:10.3189/2015JoG14J156.

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                    Kennedy, Joseph H., & Pettit, Erin C. The response of fabric variations to simple shear and migration recrystallization.  United States.  https://doi.org/10.3189/2015JoG14J156

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                    Kennedy, Joseph H., and Pettit, Erin C. Mon .  
"The response of fabric variations to simple shear and migration recrystallization".  United States.  https://doi.org/10.3189/2015JoG14J156.  https://www.osti.gov/servlets/purl/1187919.

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@article{osti_1187919,

  title        = {The response of fabric variations to simple shear and migration recrystallization},

  author       = {Kennedy, Joseph H. and Pettit, Erin C.},

  abstractNote = {The observable microstructures in ice are the result of many dynamic and competing processes. These processes are influenced by climate variables in the firn. Layers deposited in different climate regimes may show variations in fabric which can persist deep into the ice sheet; fabric may 'remember' these past climate regimes. In this paper, we model the evolution of fabric variations below the firn–ice transition and show that the addition of shear to compressive-stress regimes preserves the modeled fabric variations longer than compression-only regimes, because shear drives a positive feedback between crystal rotation and deformation. Even without shear, the modeled ice retains memory of the fabric variation for ~200 ka in typical polar ice-sheet conditions. Our model shows that temperature affects how long the fabric variation is preserved, but only affects the strain-integrated fabric evolution profile when comparing results straddling the thermal-activation-energy threshold (~–10°C). Even at high temperatures, migration recrystallization does not eliminate the modeled fabric's memory under most conditions. High levels of nearest-neighbor interactions will, however, eliminate the modeled fabric's memory more quickly than low levels of nearest-neighbor interactions. Finally, our model predicts that fabrics will retain memory of past climatic variations when subject to a wide variety of conditions found in polar ice sheets.},

  doi          = {10.3189/2015JoG14J156},

  journal      = {Journal of Glaciology},

  number       = 227,

  volume       = 61,

  place        = {United States},

  year         = {Mon Jun 01 00:00:00 EDT 2015},

  month        = {Mon Jun 01 00:00:00 EDT 2015}

}

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