Greenland is twisting, tensing and shrinking due to the ‘ghosts’ of melted ice sheets
Tectonic processes and “ghosts” of ancient ice sheets twist, lift and pull Greenland in different directions, new research reveals.
Greenland sits on the North American tectonic plate, which has pulled the island northwestward 0.9 inches (23 millimeters) per year over the past two decades. Researchers have been monitoring this drift for some time, but a new study analyzing satellite data has found that the movement and other distortions have much more to do with simple plate tectonics.
Berg and his colleagues analyzed data from 58 Global Network Satellite System (GNSS) stations in Greenland that record the island’s horizontal and vertical movements, and from nearly 2,900 GNSS stations around the North American Plate. The researchers fed that data into a model, and when they removed the effect of the North American plate on Greenland, they ended up with bedrock deformations—areas where the Earth’s crust was stretched or crumpled—that didn’t match the previous modeling.
In most regions, the movement of land masses is largely controlled by tectonic processes. But Greenland is different, because the island is covered by a giant ice cap and has a tumultuous glacial past, according to the study published August 28 in the Geophysical Research Journal: Solid Earth.
Ice sheets pile enormous weight on the Earth’s crust, pressing it down into the mantle – the layer of the planet that lies beneath the crust. Material displaced into the mantle by the sinking crust is pushed to the sides, creating what is called a peripheral bulge, Berg said.
When an ice sheet retreats, the mantle does not immediately return to its original shape. Due to the mantle’s slimy consistency, it takes thousands of years for material to flow back into the hump created by the charged crust. In other words, the coat “has a very long memory,” Berg said.
The mantle under and around Greenland is still adapting to changes in ice cover from Greenland’s highest point. last ice age about 20,000 years ago, which explains why the data shows the island deforming. Specifically, it appears that Greenland was responding to the retreat of the Laurentide Ice Sheet, which covered large areas of North America. until about 8,000 years ago.
The Laurentide Ice Sheet has created a peripheral bulge beneath parts of Greenland. This earlier bulge is gradually flattening, pulling areas of southern Greenland down and toward Canada, Berg said. Researchers already knew this, he said, but the new results reveal that the rate of deformation is higher than most modeling suggests.
Greenland’s ice sheet also plays a role in the island’s twisting movements. Melt water from the ice sheet contributed 13.5 feet (4.1 meters) to the 430 feet (130 m) of sea level rise recorded over the past 20,000 years, Berg said. That means Greenland lost an incredible amount of ice, which triggered a response in the mantle separate from the effect of the Laurentide Ice Sheet, he said.
The melting of the Greenland ice sheet has accelerated in recent years because of climate change. Past and current declines The ice mass in Greenland had the same general effect on the island, pushing bedrock outward and upward, Berg said.
The results offer the most detailed picture yet of Greenland’s movements, particularly how the island is contracting in some places, according to a statement. The results are important because they provide new information about how polar regions may respond to climate change and thus distort the maps we use for navigation and surveys, Berg said.
“With other guys[s] “From satellite observations, this can provide new information about ancient ice sheets and the structure of the Earth,” he added.
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