The melting of the Earth’s polar ice deforms the earth’s crust.
This change in shape is subtle, but it occurs several hundred kilometers from the ice caps. Researchers may be able to monitor change in research to understand how climate change will affect sea level; Understanding warping is also important, as scientists must be able to correct for this ground movement when measuring other types of geological processes, the study authors wrote in the journal’s August issue. Geophysical research letters.
Scientists already knew that when the ice disappears, the underlying crust changes. Imagine lifting your head off a memory foam pillow: as the weight of your head is lifted, the pillow gradually inflates, always in motion after you get out of bed. Something similar happens when a glacier recedes. The crust below, which is no longer under all this weight, rises slowly. It’s called isostatic rebound, and it’s really, really slow. In some high latitude regions, the ground still rebounds after the retreat of the ice caps at the end of the last ice age.
Related: Antarctica: the bottom of the world covered in ice (Photos)
But now the polar regions are losing ice at an increasing rate due to climate change. From 2000 to 2010, the loss of ice from Antarctic, Greenland and mountain glaciers increased by 60% compared to ice loss between 1990 and 2000, according to a paper published in 2020 in The cryosphere. This melting affects the shape of the crust, as does the loss of ice at the end of the Ice Age. But most of the research has focused on changes in the crust just under and around the ice caps. Even when researchers study more distant effects, they focus on vertical changes in crustal shape. But the movement of the crust after ice loss is three-dimensional, which means that it also moves horizontally.
Sophie Coulson, a postdoctoral researcher at the Los Alamos National Laboratory in New Mexico who conducted the research at Harvard University, wanted to take a global 3D look at the impact of ice loss in the 21st century. She and her colleagues used satellite data collected between 2003 and 2018 to search for tiny movements in the crust, comparing those changes with the loss of ice in Antarctica, Greenland, and high-latitude glaciers from year to year.
They found that in many cases the horizontal movement of the crust exceeded the vertical movement (uplift). The movement was very dependent on the amount of ice lost each year, but in the high and low loss years, most of North America on average exhibited more horizontal than vertical movement. Horizontal creep, mainly northward, peaked in 2012 at 0.017 inch (0.45 mm). In the low-loss years, this movement averaged about 0.004 inch (0.1 mm) for the continent as a whole.
In the early 2000s, ice retreated rapidly from the Antarctic Peninsula and West Antarctica, but East Antarctica gained ice. This gain and loss ended up being averaged in terms of the earth’s crust, so most of the deformation was confined to a relatively small area in the southern Pacific. The northern hemisphere was another story. Ice loss from northern latitudes was associated with an average of 0.015 inch (0.4 mm) of horizontal movement – mostly northward – each year in the northern hemisphere. This included up to 0.01 inch (0.3 mm) of movement in Canada and the United States, and up to 0.008 inch (0.2 mm) in Europe and Scandinavia.
These numbers may seem insignificant, but they add up over time. And this warping can affect how future ice loss will play out.
“In parts of Antarctica, for example, the rebound of the crust changes the slope of the bedrock below the ice sheet, and this can affect the dynamics of the ice,” Coulson told the Harvard Journal. A steeper slope means faster flow from the ice to the sea.
Originally posted on Live Science.