Thermal Convection Discovered Deep in Greenland Ice
Scientists have identified thermal convection as the cause of strange, plume-like structures previously observed deep within the Greenland ice sheet through radar imaging. This phenomenon, typically associated with the Earth's molten mantle, involves the upward transport of heat.
"While convection in an ice sheet goes against intuition, the physics are consistent due to ice being significantly softer than the Earth's mantle," stated Robert Law, a glaciologist at the University of Bergen.
The Greenland Ice Sheet: A Vital Climate Indicator
The Greenland ice sheet, covering 80 percent of the island, represents a vast reservoir of frozen water. Changes in this ice sheet are crucial for predicting future sea levels. Understanding its internal physics is essential for these predictions. Ice-penetrating radar allows scientists to study internal layers formed by compacted snow over millennia.
Unraveling Mysterious Plumes
In 2014, radar images revealed large, upward-buckling features in northern Greenland's ice, unconnected to the bedrock topography, prompting research into their origin. Earlier hypotheses included glacial meltwater freezing or migrating slippery spots. The idea of thermal convection within ice sheets had not been thoroughly tested.
Computer Models Confirm Convection
Law and his team utilized computer modeling to investigate. They created a digital model of a 2.5-kilometer-thick ice slab and simulated conditions where the ice base was warmed from below.
Using a geodynamics modeling package, which is typically used for Earth's mantle, they adjusted variables such as snowfall, ice thickness, ice softness, and surface ice movement.
Under specific conditions, the model generated plume-like upwellings that folded overlying ice layers, matching the structures seen in radar images. The model indicated that plume formation required ice near the base to be warmer and softer than standard assumptions usually allow.
The heat required for these convection upwellings in the model aligned with the continuous heat flow from Earth's interior, generated by radioactive decay within the crust and residual heat from Earth's formation. This gradual heat accumulation can warm and soften the insulating ice above it over time.
Significant Implications for Sea Level
Climatologist Andreas Born described the discovery as significant. While the ice remains solid and flows over thousands of years, this convection process has been likened to a "boiling pot of pasta."
Further research is necessary to understand the full implications of convection on the ice sheet's evolution and potential impacts on melting rates.
Law emphasized that understanding these hidden processes is vital for preparing for global coastline changes.