New Map Uncovers Hidden Heat Beneath Greenland, Potentially Transforming Climate Models

On the surface, Greenland appears as a frozen kingdom, dominated by one of the last continental ice sheets. But beneath this white expanse, the bowels of the Earth tell another, much more eventful story. A story of trapped heat, ancient tectonic movements and still active rocks, whose influence on the climate had until now never been quantified with such precision. However, it is there, several hundred kilometers deep, that a crucial part of the evolution of ocean levels takes place.

An unprecedented thermal map of the Greenlandic subsoil

For decades, researchers have tried to reconstruct temperature variations inside the Earth from indirect data, with global models with sometimes limited resolution. Today, a decisive step has been taken thanks to a study led by the University of Ottawa and published in Proceedings of the National Academy of Sciences. For the first time, a high-resolution 3D map of the temperature of the upper mantle beneath Greenland has been produced, revealing thermal contrasts much more marked than expected.

The researchers crossed several types of geophysical data collected by satellites and ground measurements, then applied an advanced probabilistic inversion method. Their analysis revealed, at a depth of 250 kilometers, exceptionally warm regions in south and east-central Greenland, in marked contrast to other much colder areas. These differences are not anecdotal. They bear witness to a geological complexity inherited from the ancient passage of the region above the Icelandic hotspot, a tectonic phenomenon still perceptible in the thermal structure of the mantle.

This mapping also reveals significant variations in the thickness of the lithosphere. Where heat rises, the earth's crust is thinner. This thermal gradient constitutes a key signal for understanding the internal dynamics of the Greenlandic subsoil.

Why Greenland's subsurface temperature is rewriting ice mechanics

The implications of these data are not limited to geology. The Earth's internal temperature directly affects the viscosity of rocks, and therefore how the soil reacts to the weight of ice. This phenomenon, known as isostatic adjustment, plays a central role in the dynamics of the polar ice caps. The warmer the mantle, the more deformable it is, which accelerates the rebound of the ground after the ice melts.

According to the analysis published in Phys.org, viscosity models constructed from these new temperatures show variations that can reach three orders of magnitude in the upper mantle. In other words, two regions located at the same depth can have very different stiffness depending on their temperature. This reality calls into question the assumptions used in classic models, which considered Greenland as a homogeneous and cold block, typical of cratonic regions.

The researchers also tested their models by comparing them with real data of vertical ground movements measured by GPS. As a result, simulations based on internal temperatures offer a much better match with observations than standard models. This link between underground heat and ground deformation provides access to a more detailed reading of the past and present behavior of the ice sheet.

A decisive lever for simulating future rises in ocean levels

Understanding how Greenland responds to melting ice is not just a matter of scientific curiosity. This knowledge directly conditions forecasts of sea level rise. Accelerated melting in a region with very reactive soil will have a stronger effect on water redistribution than in a stable region. The researchers integrated this new data into simulations spanning the last ten millennia, with revealing results. In certain coastal areas, the differences in simulated sea level exceed ten meters between a realistic 3D model and a simplified 1D model.

The same logic applies to future projections. By integrating the lateral thermal structure of the mantle, climate models become more sensitive to regional variations. This level of precision is crucial for coastal areas around the world, where a few centimeters of difference can determine the survival of an ecosystem or the vulnerability of a population. It is therefore less a technical detail than a fundamental adjustment in our way of anticipating the effects of global warming.