As Ice Melts, the Crust Moves

We know that when immense glacial ice melts, the land beneath the ice lifts since the weight of the ice is no longer pushing it down.

Now, scientists have documented the broader effects of melting glacial ice. In a recent issue of the journal Geophysical Research Letters, Sophie Coulson (Harvard University) and colleagues describe how the ground seems to shift horizontally by as much as, if not more than, the vertical shift. That shift is not localized to the immediate vicinity of the ice mass. In analyzing 15 years of data from ice melts in Greenland and the Arctic, Coulson found the ground shifted horizontally across the entire Northern Hemisphere.

While these are tiny shifts of 0.1 to 0.4 millimeters per year, scientists say that such far-flung shifts in the Earth’s crust because of the melting of ice packs are both impressive and unexpected.