New study explains why the ground in southeast Greenland is rising so fast

This is caused by weak rocks beneath this part of Greenland, combined with the melting of the ice sheet, according to researchers.

Changes to ground elevation are measured using global navigation satellite systems (GNSS). This GNSS station, with icebergs in the background, can be found in Greenland.

(Photo: Maaike Weerdesteijn)

Gunn Kristin Tjoflot Senior Adviser

Presented by: University of Oslo

Published 14 March 2025 - 00:01

Greenland is the world's largest island. It has an area of 2,166,086 square kilometres. About 81 per cent of the island is covered by ice.

This ice is mostly contained within the Greenland Ice Sheet. In some places, it is over three kilometres thick. The ice sheet loses ice mass each year due to runoff and meltwater.

Faster land uplift observed

Data from satellite-based navigation and positioning systems (GNSS) show that Greenland's southeastern coastline has faster ground uplift than the rest of the island.

Greenland's southeastern coast, here near the Kangerlussuaq Glacier, is now experiencing both extensive melting and rapid land uplift.

Ground uplift refers to changes in the elevation of the ground relative to sea level. In southeast Greenland, the ground is rising by more than 12 millimetres annually.

Two researchers from the University of Oslo, Maaike Weerdestejin and Clint Conrad, have investigated why land uplift is faster in the southeast part of the island.

All of Greenland is rising, but at different rates

Satellite measurements show that the entire coastline of Greenland is rising. One reason for this is the ongoing melting of the ice sheet due to a warmer climate.

When the ice mass is reduced, the rocks beneath the ice become decompressed. This leads to an elevation increase of a few millimeters per year.

However, the research duo also found that the speed of ground uplift varies depending on where on the island it is measured.

"In southeastern Greenland, ground uplift is occurring unusually quickly, at rates of more than 10 millimetres per year," says Clint Conrad, a professor of geophysics.

He explains that models of the glacial isostatic adjustment (GIA) were unable to explain this rapid uplift. GIA calculates the solid Earth's response to melting.

Properties of the Earth's crust and mantle

Melting of the ice sheet is only one factor that affects the rate of ground uplift. The properties of the mantle below the crust also play a major role.

In particular, viscosity. Viscosity is a measure of a fluid's resistance to movement. It influences how rocks in the Earth deform, according to the researchers.

Previous GIA models have primarily considered changes in viscosity with depth below the subsurface.

However, Weerdesteijn and Conrad used a new GIA code that can take side-to-side variations in viscosity into account.

Rocks weakened by a mantle plume

40 million years ago, due to continental drift, Greenland drifted over a mantle plume – a column of hot rock rising from the deep interior of the Earth. Today, this plume is located beneath Iceland. It remains active, driving volcanic activity and hot springs on the island.

Weerdesteijn and Conrad hypothesised that heat from this mantle plume may have weakened the rocks in the Earth's crust beneath southeast Greenland. This part of Greenland is closest to Iceland.

Using the adjusted GIA model, they reduced the viscosity to the upper mantle rocks along the path of the plume across Greenland.

Beneath Iceland is a mantle plume that rises from the Earth’s interior, fueling volcanic activity and hot springs on the island. This photo captures a recent volcanic eruption.

The new simulations showed that the rate of ground uplift was significantly faster along the historic track of the mantle plume: Uplift that would normally have happened over thousands of years instead occurs in only centuries or decades above the weakened rocks.

This explains why the southeastern part of Greenland is rising particularly fast, as this part of the island is located directly above rocks that were weakened by the hot Iceland plume.

Also happened in the Holocene

The researchers also found that a similar historical uplift event may have occurred about 10,000 years ago.

The Holocene epoch spans from 11,700 years ago to the present. Sea level indicators from this period show that the coastline of southeastern Greenland rose rapidly following extensive melting of the ice sheet at the end of the last Ice Age.

"Uplift rates in the Holocene period may have been almost twice as high as those we see today. This indicates that there is potential for even faster land uplift in the future as melting in Greenland accelerates," says Maaike Weerdesteijn.

She explains that such uplift is important because it changes the elevation of the glaciers as they enter the ocean. This can affect the rate of ice mass loss.

Reference:

Weerdesteijn, M.F.M. & Conrad, C.P. Recent ice melt above a mantle plume track is accelerating the uplift of Southeast Greenland, Communications Earth & Environment, vol 5, 2024. DOI: 10.1038/s43247-024-01968-6