Greenland: Warped, Strained, and Diminishing from Ice Sheet Meltdown's Lingering Effects

Researchers followed Greenland’s shifts utilizing information gathered from the island’s numerous satellite facilities.(Image credit: Christian Solgaard)

Geologic occurrences in conjunction with the “memories” of previous glaciers are misshaping, elevating, and tugging Greenland in assorted ways, according to new investigations.

Greenland rests upon the North American continental plate, which has been pulling the landmass northwest by 0.9 inches (23 millimeters) annually for the prior two decades. This motion has been under scrutiny by investigators for a while, however, a fresh analysis of data from satellites has determined that the movement, along with other alterations, involves more than just plate tectonics.

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Berg alongside his team examined information from 58 Global Network Satellite System (GNSS) facilities in Greenland, recording the island’s movements both horizontally and vertically, as well as close to 2,900 GNSS facilities circling the North American plate. The data collected was incorporated into a model. Following the removal of the influence of the North American plate on Greenland, the team was confronted with bedrock deformations, areas where the planet’s outer layer had been either stretched or buckled, which didn’t align with prior modeling.

In most locations, the shifts in landmasses are predominantly affected by geological actions. However, Greenland stands out because a massive ice sheet covers the landmass, and it carries a history marked by glacial upheaval, according to the study, which was featured on Aug. 28 in the Journal of Geophysical Research: Solid Earth.

Ice sheets apply immense strain on the Earth’s shell, compressing it down into the mantle — the layer of the world existing below the crust. As a result, substance displaced within the mantle by the subsiding crust is forced laterally, leading to what is known as a peripheral forebulge, Berg pointed out.

Whenever an ice sheet withdraws, the mantle’s restoration to its initial form is not immediate. Attributed to the mantle’s sticky nature, the process of material returning to the cavity produced by the pressurized crust requires millennia. As Berg stated, the mantle “has an extended memory.”

A depiction demonstrating the northward drift enforced by the North American geologic plate. The sites of satellite stations are marked with red circles.

The adjustments of the mantle beneath Greenland, resulting from transformations in ice coverage since the peak of the last ice period nearly 20,000 years ago, shed light on the island’s noticeable distortions. It seems Greenland is reacting to the Laurentide Ice Sheet’s retreat, which once enveloped vast stretches of North America until approximately 8,000 years ago.

The Laurentide Ice Sheet gave rise to a peripheral forebulge underneath specific areas of Greenland. As Berg stated, this forebulge is gradually deflating, dragging regions in southern Greenland downward and toward Canada. While this was already understood by investigators, the updated results suggest that the degree of distortion surpasses projections made by most models.

The Greenland Ice Sheet also is a factor in the island’s spinning motions. Berg noted that meltwater originating from the ice sheet has added 13.5 feet (4.1 meters) to the recorded sea-level swell of 430 feet (130 m) over the past 20,000 years. Implying that Greenland has shed a remarkable quantity of ice, consequently activating a reaction within the mantle that is distinct from the Laurentide Ice Sheet’s consequences, he clarified.