Can we prepare for the impact of melting glaciers? | BBC News

Key Concepts

• Erett Glacia Initiative: A project aimed at improving sea level rise forecasts by understanding glacial dynamics.
• Pressure Melting Temperature: The temperature at which ice at the base of a glacier begins to melt due to pressure, facilitating ice flow.
• Ring Shear Device: A laboratory apparatus used to simulate and study the interaction between ice and the substrate at the base of glaciers.
• Till: Sediment deposited directly by a glacier, often with a fine composition suitable for simulating glacial beds.
• Ice Bed Interface: The crucial boundary between the bottom of a glacier and the underlying rock or sediment.

Understanding Glacial Flow and Sea Level Rise

The primary focus of the Erett Glacia Initiative, co-founded by Dr. Brent Mchu, is to enhance the accuracy of sea level rise forecasts. While significant progress has been made in understanding glacier flow, particularly ice sheet behavior, fundamental questions remain. A key area of uncertainty is the mechanism by which ice slides over the underlying mud and rock, as this directly dictates the speed of glacial flow, which in turn determines future sea level rise.

Simulating the Ice Bed Interface in the Lab

To address these uncertainties, the Erett Glacia Initiative supports scientists at the University of Wisconsin who are investigating the interactions at the ice bed interface. The geological composition of sediments found beneath glaciers in Antarctica is similar to till deposits found in areas like Lake Michigan, which were formed by ancient glaciers. These till samples are collected and utilized in laboratory experiments.

The challenge in studying the ice bed interface is that it is typically located deep beneath ice sheets, often at depths of 2 kilometers. Direct study in situ is extremely difficult. Therefore, researchers employ laboratory simulations to replicate these conditions in a controlled environment.

The Ring Shear Device: A Tool for Glacial Research

A central piece of equipment for these experiments is a ring shear device. This machine is designed to simulate the conditions at the base of a glacier. It involves:

1. Ice Ring Formation: A ring or donut-shaped piece of ice is created.
2. Substrate Simulation: This ice ring is pressed against a substrate material that mimics the sediment found at the bottom of a glacier. The sediment used is actual till collected from glacial environments.
3. Simulated Glacial Conditions: The device spins the ice at a rate comparable to glacial movement and applies pressures equivalent to those found at the base of a glacier.

This setup allows researchers to study the ice bed interface under conditions highly representative of natural glacial environments.

Experimental Setup and Process

The operation of the ring shear device involves a detailed setup process:

1. Hydraulic Press and Gripping: A hydraulic press applies pressure to the base of the instrument. Teeth are embedded in the base to grip the ice.
2. Freezing the Ice: Water is introduced around the teeth, and the temperature is lowered to approximately -8°C. The ice is allowed to freeze for three to four days to ensure it is fully integrated with the teeth.
3. Preventing Sticking: Once the ice is frozen, the outer walls of the chamber are warmed slightly to prevent the ice from sticking to them.
4. Initiating Shearing: The ice is then spun very slowly.
5. Melting Mechanism: The shearing action itself generates heat, causing the ice at the interface to reach its pressure melting temperature and melt.
6. Data Collection: A camera captures the processes occurring within the tank, and the collected data is used to refine the physics incorporated into ice sheet models.

Impact on Sea Level Rise Predictions

The data generated from these laboratory experiments is crucial for improving the accuracy of ice sheet models. These models, in turn, are essential for making more reliable predictions about future sea level rise. By understanding the fundamental mechanics of how ice slides over its bed, scientists can provide better forecasts, enabling the world to prepare for the impacts of rising sea levels.

Conclusion

The Erett Glacia Initiative is employing innovative laboratory techniques, particularly the ring shear device, to unravel the complexities of glacial ice flow. By simulating the critical ice bed interface and collecting precise data, researchers are working to enhance the predictive capabilities of ice sheet models, ultimately leading to more accurate sea level rise forecasts and better global preparedness.