The PNAS study used satellite, seismic, gravity and heat‑flow data to build 3D models of the upper mantle beneath Greenland and northeastern Canada. It found unexpectedly large temperature differences tied to Greenland’s passage over the Iceland hotspot, which make mantle rocks softer and alter crustal rebound. These subsurface variations affect glacier motion and the timing of water input to the ocean, meaning sea‑level projections could be biased if mantle heat is ignored. Improved 3D Earth–ice models will sharpen forecasts and aid adaptation planning.
3D Mantle Models Reveal Unexpected Heat Beneath Greenland — What That Means For Sea‑Level Rise
Scientists have discovered unexpectedly large temperature variations deep beneath Greenland’s ice sheet that could change how researchers forecast future sea‑level rise. Using advanced three‑dimensional models of Earth’s upper mantle, the team mapped subsurface heat that affects how the crust responds as ice is lost.
How the Study Was Done
The paper, published in Proceedings of the National Academy of Sciences (PNAS), combined satellite observations, seismic surveys, gravity measurements and heat‑flow records to build detailed 3D images of the mantle beneath Greenland and northeastern Canada. This integrated approach reveals variations that are not apparent from surface observations alone.
Hotspot Legacy and Crustal Response
The models trace residual heat left by Greenland’s passage over the Iceland hotspot — a long‑lived, high‑temperature upwelling in the mantle. That lingering warmth makes mantle rocks mechanically softer, so the crust bends and rebounds differently under ice loads.
"This research advances our understanding of the Earth's internal structure beneath Greenland," said Professor Glenn Milne of the University of Ottawa, the study's lead author.
Why It Matters For Sea‑Level Rise
These subsurface temperature variations influence glacial isostatic adjustment — the rate at which bedrock rebounds when ice melts — and can also affect glacier motion. Because Greenland is currently responsible for roughly 20% of observed global sea‑level rise, changes in how quickly and where water is delivered to the ocean matter for projections used by planners and coastal communities.
If mantle heat and crustal structure are not fully accounted for, projections of future sea levels could be biased. Incorporating 3D mantle structure into Earth–ice models will improve the timing and magnitude estimates of ice loss and ocean input.
Implications For Policy and Adaptation
Better Earth and ice modeling gives policymakers more reliable information for resilience planning — from coastal defenses and wetland restoration to updated building codes. At the same time, the study reinforces that cutting greenhouse‑gas emissions remains essential to slow long‑term ice loss: expanding renewables, electrifying transport and buildings, and adopting science‑based climate policies are still critical.
Looking Ahead
Future work will refine these 3D models and incorporate them into coupled ice‑sheet and sea‑level simulations. The results emphasize that both surface climate change and deeper Earth processes must be considered for accurate sea‑level forecasts.
