New Research Links Greenland's Uneven Ice Loss to Earth's Mantle Heat

Unveiling Subsurface Dynamics Beneath Greenland

New research has shed light on a critical factor influencing the melting of the Greenland Ice Sheet: variations in Earth's mantle temperature. A study led by Dr. Parviz Ajourlou from the University of Ottawa, in collaboration with partners from the University of Twente in the Netherlands and the Geological Survey of Denmark and Greenland, has developed high-resolution 3D models of the Earth's thermal structure beneath Greenland and northeastern Canada.

These models reveal 'significant lateral variations in the Earth's thermal structure beneath Greenland,' according to Dr. Ajourlou. This understanding is crucial for interpreting Greenland's tectonic history and how it influences the geophysical properties of the underlying rocks.

The Influence of Geothermal Heat on Ice Behavior

The study emphasizes that deep heat plays a substantial role in shaping ice behavior. Greenland's crust has been formed by volcanic activity, slow plate motions, and changes within the mantle, creating a mix of hotter and cooler zones beneath the island. These zones directly affect how the ice sheet moves. Warmer rock reduces resistance where the ice meets the ground, allowing ice to slide more easily in certain areas.

Basal melting, which is the melting of ice from below, is partly dependent on geothermal heat flux—heat emanating from Earth's interior. Earlier mapping identified a band of elevated geothermal heat under Greenland, consistent with an Iceland plume track. This ancient and long-lived source of heat, stemming from when Greenland moved over the Iceland mantle plume millions of years ago, has created regions where subglacial meltwater is abundant, lubricating the base of the ice and accelerating its flow.

Implications for Ice Loss and Sea Level Predictions

The discovery of these temperature contrasts helps explain why some regions of the Greenland Ice Sheet thin faster than others and why satellite instruments detect uneven patterns of gravity and height change across the ice sheet. Even slight shifts in heat at depth can alter the strength of the bedrock, affecting how the crust sinks or rises as ice is added or removed.

From 1992 to 2020, Greenland lost approximately 5.4 trillion short tons of ice. In 2023 alone, the island lost about 195 billion short tons of ice. Project lead Glenn Milne, a Professor at the University of Ottawa, highlighted that 'temperature variations directly influence the interaction between the ice sheet and the bedrock, which must be quantified to interpret observations of land motion and gravity changes.' This research is vital for improving how scientists model ice-Earth interactions, leading to more accurate forecasts of future sea level rise and enabling better planning.

Integrating Deep-Earth Processes into Climate Models

This work underscores the importance of integrating deep-Earth processes into climate models. Previous models often oversimplified the effect of the lithosphere, the Earth's crust and upper mantle, on ice sheets. The findings indicate that the geothermal anomaly resulting from the Iceland mantle plume tens of millions of years ago is a significant driver for the hydrology under the ice sheet and the high flow-rate of the ice today. Understanding this complex interplay between geothermal heating and the Greenland Ice Sheet is crucial for comprehensive climate studies.