As glaciers and ice sheets melt and calve into our oceans, they are contributing to a rapid rise in global sea levels, reaching unprecedented rates. To effectively anticipate and mitigate future sea-level rise, scientists must deepen their understanding of glacier melt rates and the factors influencing their flow.
Recent research from MIT provides fresh insights into glacier dynamics, focusing on the microscopic deformations within the ice. The findings indicate that the flow of a glacier is heavily influenced by the movement of microscopic defects within the ice structure.
Through their study, the researchers discovered that they could predict the flow of a glacier by analyzing the prevalence of specific types of microscopic defects. This relationship between micro-level changes and macro-scale glacier behavior led to the formulation of a novel model for glacier flow. Utilizing this model, the team mapped the flow of ice in various regions of the Antarctic Ice Sheet.
Interestingly, their results challenge established beliefs, revealing that the Antarctic Ice Sheet is not a singular entity but rather exhibits diverse flow patterns in response to climate-induced stresses. The researchers note that their findings “significantly reshape the climatic conditions under which marine ice sheets may become unstable, potentially leading to swift rates of sea-level rise.”
“This research highlights the influence of microscale processes on broader behavior,” states Meghana Ranganathan, PhD ’22, who spearheaded the study as a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) and has since become a postdoctoral researcher at Georgia Tech. “These mechanisms operate at the molecular level and can ultimately impact the stability of the West Antarctic Ice Sheet.”
Co-author and EAPS Associate Professor Brent Minchew adds, “Glaciers are indeed accelerating, though there’s considerable variability in this behavior. This is the first study bridging laboratory findings to real-world ice sheets, evaluating the stability of ice in its natural environment, which will enhance our understanding of catastrophic sea-level rise probabilities.”
The full study by Ranganathan and Minchew was published in the Proceedings of the National Academy of Sciences this week. Read the study here.
Understanding Glacier Flow
Glacier flow refers to the ice movement from the glacier’s peak or the center of an ice sheet down towards the edges, where it eventually breaks off and contributes to ocean waters. This typically slow process has been a significant factor in the gradual increase of the world’s average sea level.
However, in recent years, ocean levels have surged at alarming rates, driven primarily by global warming and the accelerated breakdown of glaciers and ice sheets. While it is well-established that polar ice loss is a major contributor to this phenomenon, it also introduces significant uncertainty in predictive models.
“Part of the challenge is scaling,” explains Ranganathan. “Many fundamental processes dictating ice flow occur on scales that are challenging to observe. Our aim was to pinpoint these microphysical processes that control ice movement, which have not been adequately captured in existing models of sea-level change.”
The team’s work builds on earlier findings from researchers at the University of Minnesota, who explored the deformation of small ice chips under stress in the early 2000s. They identified two primary mechanisms for ice flow: “dislocation creep,” where cracks at the molecular level migrate, and “grain boundary sliding,” where individual ice crystals shift against one another, causing movement at the boundaries.
These studies pointed out that the ice’s sensitivity to stress—its likelihood to flow—varies based on which mechanism is dominant. Notably, ice is more responsive to stress during dislocation creep than during grain boundary sliding.
Recognizing the implications of these microscopic processes, Ranganathan and Minchew aimed to redefine current models addressing ice flow on glacial scales.
“Existing models for sea-level rise often rely on a single, consistent value for ice sensitivity to stress across an entire ice sheet,” says Ranganathan. “What we learned is that ice sensitivity actually varies significantly depending on which mechanisms are dominant.”
Mapping Sensitivity
In their new exploration, the MIT team leveraged insights from previous research to create a model estimating the sensitivity of specific icy regions to stress, which plays a vital role in the likelihood of their flow. This model integrates factors such as environmental temperature, ice crystal sizes, and total ice mass in a given area. It then calculates the proportion of deformation attributed to dislocation creep versus grain boundary sliding, ultimately providing an estimate of the region’s stress sensitivity.
The researchers applied their model to empirical data collected from multiple sites across the Antarctic Ice Sheet, where previous observations had documented metrics like local ice height, crystal dimensions, and temperatures. They generated a detailed map illustrating ice stress sensitivity, and when compared to existing satellite and field data, they found a strong correlation, highlighting the model’s potential in forecasting future glacier and ice sheet behavior.
“As climate change results in glacier thinning, it could alter the ice’s sensitivity to stress,” notes Ranganathan. “The instabilities anticipated in Antarctica may differ significantly, and our model now allows us to capture these variations.”
Photo credit & article inspired by: Massachusetts Institute of Technology
