Mystery Solved: Scientists Finally Explain the Strange Swirls Hidden Deep in Greenland’s Ice

For more than a decade, glaciologists studying the Greenland Ice Sheet have noticed something unusual buried deep within it. Radar surveys revealed distorted internal layers that appeared to bulge upward in broad, swirling plume-like shapes. These features did not match the expected patterns produced by normal ice flow or underlying bedrock. Their origin remained unclear. A new study published in The Cryosphere now provides a strong explanation. Researchers conclude that the mysterious structures are most consistent with thermal convection occurring deep within the ice sheet.

What Radar Revealed Beneath the Ice

Scientists study the internal structure of ice sheets using ice-penetrating radar. These instruments transmit radio waves downward through the ice and measure how much of the signal reflects back. The reflections create layered images that preserve records of past snowfall and long-term deformation. Normally, these internal layers appear smooth and gently curved in response to gravity-driven ice flow.

In northern Greenland, however, researchers identified plume-shaped distortions rising from deep within the ice column. These structures were several hundred meters wide and extended upward from lower layers. They did not align with surface slopes or basal topography. Because internal ice layers function like geological time markers, any distortion suggests an underlying physical process. Previous explanations included unusual ice flow patterns or localized basal heating, but none fully accounted for the geometry observed in radar data.

Testing the Thermal Convection Hypothesis

The new research team, led by geophysicists and glaciologists, explored whether thermal convection could explain the formation of plumes. Thermal convection occurs when warmer, less dense material rises through cooler, denser material. It is a process commonly associated with Earth’s mantle, where hot rock slowly circulates over millions of years.

The researchers adapted numerical modelling tools originally designed for mantle dynamics. These computer simulations solve equations describing heat transfer and slow viscous flow. Ice under high pressure behaves as a very slow-moving viscous material rather than as a rigid solid. By inputting realistic temperature gradients, geothermal heat values, and ice rheology parameters, the model produced plume-like structures that closely matched the radar observations. The study reported strong agreement between modelled convection patterns and actual radar stratigraphy. According to the authors, the results show that thermal convection is physically plausible within certain deep regions of the Greenland Ice Sheet if the ice is softer than previously assumed.

Why Ice Can Behave Like a Flowing Fluid

At the surface, ice behaves like a brittle material, prone to fracture and cracking. Deep within the ice sheet, conditions differ significantly. The Greenland Ice Sheet is several kilometres thick in places. Pressure increases with depth, and temperatures approach the melting point. Under these conditions, ice deforms slowly under stress.

Geothermal heat rising from Earth’s interior contributes additional warming at the base. Friction generated by ice movement also produces heat. When temperature differences develop between lower and upper layers, density contrasts can drive extremely slow convection currents over thousands of years. Dr. Thomas Law, lead author of the study, explained in the publication that the viscosity of deep ice may be up to ten times lower than standard ice sheet models assume. Lower viscosity allows material to circulate more easily, enabling the formation of convective plumes.

Implications for Ice Sheet Modelling

Understanding the internal dynamics of the Greenland Ice Sheet is essential for predicting future sea level rise. Most ice sheet models focus on surface melting, basal sliding, and large-scale flow toward the ocean. The discovery of possible deep convection suggests that internal heat transport may also influence long-term behaviour.

Convective circulation can redistribute heat within the ice column, potentially affecting how quickly basal ice approaches melting conditions. Changes in basal temperature influence sliding speed and ice discharge into the ocean. If deep ice is softer and more dynamic than assumed, projections of Greenland’s future mass loss may require adjustment. The findings do not imply rapid or dramatic changes, but they introduce an additional mechanism that models must incorporate to improve accuracy.

Connecting Deep Processes to Climate Change

The Greenland Ice Sheet plays a major role in global sea level. Even small changes in its internal dynamics can have long-term implications. While the swirling plumes exist far below the surface, they are part of a system that ultimately connects to coastal communities worldwide.

The study reinforces a broader scientific understanding that ice sheets are not static bodies of frozen water. They are complex physical systems influenced by surface climate, internal heat flow, and interactions with the solid Earth below.

A Complex Picture of Polar Ice

The discovery of thermal convection inside the Greenland Ice Sheet reshapes how scientists view its internal structure. What once appeared to be unexplained distortions in radar data now fit within established physical principles. The same process that drives mantle circulation beneath continents may also occur, at a much slower pace, within polar ice.

As measurement techniques improve and numerical models become more sophisticated, researchers expect to uncover additional hidden processes within ice sheets. Solving the mystery of Greenland’s swirling plumes highlights how much remains to be learned about Earth’s coldest environments and how those environments influence global change.