So much ice melts that the Earth’s crust is in motion

Ice melting in Greenland and Antarctica is contributing to the lateral slide of the Earth’s crust, even in places more than 1,000 kilometers away. Between 2003 and 2018, melting ice in Greenland and the glaciers of the Arctic led to horizontal displacement of the earth across much of the Northern Hemisphere.

As the continents’ frozen burdens dissipate, the ground deforms-not only in the immediate vicinity of the glaciers, but also in distant places.

The loss of melting ice from land masses such as Greenland and Antarctica causes the Earth’s crust to warp slightly, even in places more than 1,000 kilometers from where the ice is lost.

Melting ice removes mass from the Earth’s continents. Freed from its gravity, the earth, which was once covered by ice, rises upward. This vertical response has been fairly well studied, but Sophie Coulson of Harvard University in Cambridge, Massachusetts, and her colleagues wanted to analyze how the earth shifts horizontally.

They collected satellite data on ice loss in Greenland, Antarctica, mountain glaciers, and ice caps and combined it with a model of how the Earth’s crust responds to changing mass.

Between 2003 and 2018, melting ice from Greenland and Arctic glaciers caused horizontal ground displacement across much of the Northern Hemisphere, with most of Canada and the United States at 0.3 millimeters per year. In some areas, even away from the melting ice, the horizontal movement was greater than the vertical movement.

(a) Predicted average crustal deformation rates generated by ice-mass loss across the Greenland Ice Sheet from 2003–2018 (Smith et al., 2020). (b) Predicted crustal deformation rates across North America and Europe, in years of relatively high (2012) and low (2006) mass loss from the Greenland ice sheet. Yearly spatial ice-mass loss is inferred from an analysis of GRACE gravity data (see text). Vertical motion is given by the red-blue color scale and tangential motions are represented as arrow vectors. Tangential motions in the vicinity of Greenland are excluded in order to highlight the far-field response.

Geophys. Res. Lett. (2021)

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