The landscape under the Greenland Ice Sheet is now almost mapped

Published 18-04-2024

An overview of the geology beneath the ice sheet is useful to understand the melting, the occurrence of valuable raw materials, and the formation of continents.

The updated map of the landscape under the ice sheet is based on a large amount of geophysical data and scientific consensus on how to interpret them. (Illustration: Mac Gregor et al.)

For as long as humans have been on Earth, large parts of Greenland have been hidden under ice. So far, no one has known what it looks like underneath the frozen cover.

But now an international research team has created a data-based map of how 80 percent of the geology beneath the ice sheet is most probably composed.

The map has just been published in the scientific journal Geophysical Research Letters and is freely available in the GEUS Dataverse.

“Within the past five years, we have acquired such advanced imaging technology that we can begin to see the bottom and deep valleys under the ice. We have gradually collected enough data to get a picture of how the bottom of the ice has split up and moved,” explains glaciologist William Colgan, who is a co-author on the study and Senior Researcher at the Geological Survey of Denmark and Greenland (GEUS).

The map provides useful knowledge

Knowledge of what the geology looks like under the Greenland Ice Sheet is important for several reasons:

  • Melting: As the ice melts and breaks up, its movements are determined by the topography below. When the globe gets warmer, it is an advantage to be able to predict how the giant ice masses will behave.
  • Raw materials: Under the ice, there can be critical raw materials, which are crucial elements in, among other things, wind turbines, batteries, solar cells, and other technologies that are necessary in the green transition. When the geology under the ice is mapped, you can get an idea of whether there are valuable raw materials.
  • Knowledge of the Earth: Part of the answer to how the earth’s continents were formed billions of years ago may be hidden under the ice sheet.

The map is based on scientific consensus

In addition to the image material, William Colgan and the other researchers behind the new mapping have taken geophysical data as their starting point. These are, for example, magnetic and seismic signals measured from satellites and aircraft and with seismometers.

Authors from four different countries have jointly compiled and interpreted the extensive data material. This way, they have reached an agreement on what the map of the subglacial landscape should look like – most likely!

“It's not a definitive map, but it's the best and most qualified bid so far,” says William Colgan.

First update in 25 years

So far, the best guess at how the geology is shaped under the ice has been depicted on a map hand-drawn in 2009 by geologist Peter Dawes from GEUS.

Peter Dawes’ 25-year-old map looks very different from the new one: he drew the map’s tectonic lines based on knowledge of the geology in the ice-free part of Greenland.

Subglacial map Greenland

Above is Peter Dawes map B to the left and the new map A to the right. (Illustration: Mac Gregor et al.)

The tectonic lines on the updated map are still hand-drawn. But new technologies have made it possible to include much more data in the assessment of where they run.

“We have compared the geophysical data to what has been published about the basal geology. When we combine the different data sets, we get a more complete picture of Greenland’s geology,” says geologist Thomas E. Kokfelt from GEUS.

Thomas E. Kokfelt has contributed to the new mapping with his knowledge of the geology in the ice-free part of Greenland.

Although the new map of the subglacial landscape is far more detailed than the previous one, it is still not complete: three areas under the ice are missing (the white areas on the map).

This is because there is still uncertainty about how data from the three areas should be interpreted.

William Colgan
Senior Researcher
Glaciology and Climate
Anne Ringgaard
Communications Officer
Press and Communication
Thomas Find Kokfelt
Senior Researcher
Mapping and Mineral Resources

The scientific article

"Geologic Provinces Beneath the Greenland Ice Sheet Constrained by Geophysical Data", published in Geophysical Research Letters, April 2024

Authors: Joseph A. MacGregor, William T. Colgan, Guy J.G Paxman, Kirsty J. Tinto, Beáta Csathó, Fiona A. Darbyshire, Mark A. Fahnestock, Thomas F. Kokfelt, Emma J, MacKie, Mathieu Morlighem, Olga V. Sergienko