GPS World

Tag: DTU Space

  • Greenland is twisting and stretching, GNSS data shows

    Greenland is twisting and stretching, GNSS data shows

    Greenland is being twisted, compressed and stretched, according to researchers in the Department of Space Research and Space Technology of the Technical University of Denmark (DTU Space). As a result, the entire island has shifted northwest over the past 20 years by about 2 centimeters per year.

    GNSS data shows plate tectonics and movements in the bedrock caused by the melting of large ice sheets, reducing pressure on the subsurface. The pressure is easing both because large amounts of ice have melted in Greenland in recent years, and because the bedrock is still affected by the enormous ice masses that have melted since the peak of the last Ice Age around 20,000 years ago.

    Horizontal land motion observed by the 58 GNET stations used in this study, processed in the IGS14 reference frame. Their location is shown by the colored circles together with their labels. The boundaries of Greenland's drainage basins are shown in green with numbers (1) to (7b). The Greenland Ice Sheet (GrIS) is represented in white and peripheral glaciers in Greenland (GrPG) and Arctic Canada (CanPG) are highlighted in black and purple respectively. (Image: Study authors)
    Horizontal land motion observed by the 58 GNET stations used in this study, processed in the IGS14 reference frame. Their location is shown by the colored circles together with their labels. The boundaries of Greenland’s drainage basins are shown in green with numbers (1) to (7b). The Greenland Ice Sheet (GrIS) is represented in white and peripheral glaciers in Greenland (GrPG) and Arctic Canada (CanPG) are highlighted in black and purple respectively. (Image: Study authors)

    The new measurements are based on 58 GNSS stations placed around Greenland. They measure Greenland’s overall position, elevation changes in the bedrock, and how the island is shrinking and stretching. The movements are causing Greenland to both expand and contract horizontally. The effect is that Greenland’s area is currently being “stretched out” and becoming slightly larger in some regions, while others are being “pulled together.”

    ”Overall, this means Greenland is becoming slightly smaller, but that could change in the future with the accelerating melt we’re seeing now,” said DTU Space postdoc researcher Danjal Longfors Berg, lead author of the article in the Journal of Geophysical Research.

    It is the first time the horizontal movements have been described in such detail.

    ”We have created a model that shows movements over a very long timescale from about 26,000 years ago to the present. At the same time, we have used very precise measurements from the past 20 years, which we use to analyze the current movements. This means we can now measure the movements very accurately,” Berg said.

    Important for surveying and navigation

    The new research provides useful information about what happens when climate change hits the Arctic with accelerating speed, as is the case in these years.

    ”It’s important to understand the movements of landmasses. They are of course interesting for geoscience. But they are also crucial for surveying and navigation, since even the fixed reference points in Greenland are slowly shifting,” Berg said.

    The GNSS stations are owned by the Climate Data Authority under the Ministry of Climate, Energy and Utilities. They are used for research purposes and operated in collaboration with DTU Space. The research is conducted under the DTU Space research center Center for Ice-Sheet and Sea-Level Predictions (CISP).

  • GPS reveals Antarctic bedrock rising

    The entirety of West Antarctica contains enough ice that, if it were to melt, would cause oceans to rise 10 feet. While the West Antarctic ice sheet is at risk of collapse, GPS data suggests this crisis could be averted because the bedrock supporting it is rising.

    Using GPS, an international team of researchers found that the viscosity of the mantle under the West Antarctic Ice Sheet is much lower than expected, with the crust rebounding faster than expected, possibly stabilizing against catastrophic collapse. According to the study, in 100 years, the uplift rates at the GPS sites will be 2.5 to 3.5 times more rapid than currently observed.

    Backer Islands GPS station: The small mushroom-shaped GPS antenna is supported by the nearby equipment with solar panels. (Photo: David Saddler via Colorado State University)
    Backer Islands GPS station: The small mushroom-shaped GPS antenna is supported by the nearby equipment with solar panels. (Photo: David Saddler via Colorado State University)

    Participating researchers led by scientists at the Ohio State University installed a series of GPS stations on rock outcrops around the region to measure the Earth’s rise in response to thinning ice. Measurements showed that the bedrock uplift rates near the coast of West Antarctica were as high as 1.6 inches per year, one of the fastest rates ever recorded in glacial areas.

    “This very rapid uplift may slow the runaway wasting and eventual collapse of the ice sheet,” said Rick Aster, a co-author of the study from Colorado State University. Nevertheless, Aster told the UK’s Independent, “To keep global sea levels from rising more than a few feet during this century and beyond, we must still limit greenhouse gas concentrations in the atmosphere, which can only occur through international cooperation and innovation.”

    The team also included DTU Space. Study results were published in the journal Science.