Microscopic Defects in Ice Influence Glacier Flow, Study Shows

By IndraStra Global News Team

Melting glaciers and ice sheets are rapidly raising global sea levels. To predict future sea-level rise, scientists need to better understand glacier melt rates and flow influences. An MIT study reveals that glacier flow is significantly affected by microscopic defects in the ice.
The researchers discovered they could estimate a glacier's flow by examining its susceptibility to different types of microscopic defects. They used this insight to create a new model of glacier flow and mapped ice movement across the Antarctic Ice Sheet. Contrary to previous beliefs, they found the ice sheet's flow is varied and influenced by warming. This new understanding of micro-to-macro deformation processes suggests that marine ice sheets might become unstable under different climate conditions than previously thought, potentially leading to rapid sea-level rise.
Meghana Ranganathan, who led the study, highlights how small-scale processes impact large-scale ice sheet behavior. Co-author Brent Minchew notes that this research bridges laboratory findings to natural ice sheet stability, enhancing predictions of catastrophic sea-level rise.
Glacier flow refers to the movement of ice from the top or center of a glacier down to the edges, where it eventually breaks off and melts into the ocean, contributing to rising sea levels over time. Recently, sea levels have risen rapidly due to global warming and the faster melting of glaciers and ice sheets. The melting of polar ice is a major but unpredictable factor in sea-level rise.
Ranganathan explains that the challenge lies in understanding the small-scale mechanisms that cause ice to flow, which need to be represented in current models. Their study builds on early 2000s experiments by University of Minnesota geologists, who identified two microscopic mechanisms of ice flow: "dislocation creep" and "grain boundary sliding." They found that ice is more sensitive to stress and thus more likely to flow when dislocation creep dominates over grain boundary sliding.
Ranganathan and Minchew realized these microscopic findings could change how we understand glacier flow on a larger scale. Current sea-level rise models assume a constant sensitivity of ice to stress across an ice sheet, but these experiments showed significant variability due to the different mechanisms at play.
In their new study, the MIT team used insights from previous experiments to create a model estimating an icy region's sensitivity to stress, which influences how likely the ice is to flow. The model factors in ambient temperature, average ice crystal size, and estimated ice mass to calculate deformation due to dislocation creep or grain boundary sliding. Based on the dominant mechanism, the model estimates the region's sensitivity to stress.
The scientists input real data from various locations across the Antarctic Ice Sheet, including local ice height, ice crystal size, and temperature. Using these inputs, they produced a map showing ice sensitivity to stress across the ice sheet. This map closely matched satellite and field measurements, indicating the model's accuracy in predicting glacier and ice sheet flow.
Ranganathan notes that as climate change thins glaciers, it could change ice sensitivity to stress. The new model can capture these differences, better predicting Antarctic ice sheet instabilities.
 With reporting by MIT News.

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