New research reveals that melting polar ice sheet ice is not only raising sea levels, but also causing a shift in the Earth's underlying surface. Some of these effects can be seen over thousands of miles.
The Earth's crust is expanding and rising as the Arctic Islands, Greenland and Antarctica are losing their ice. Although the movement isn’t massive, it averages less than one millimeter per year, it’s still there and covers a lot.
A feedback loop is also happening because the bedrock beneath the ice changes, which in turn affects how the melts and breaks apart. It is crucial to understand how this works in order to model how the world may look in the future.
Sophie Coulson, geophysicist at Los Alamos National Laboratory, New Mexico, says that scientists have done a lot under ice sheets and glaciers.
"They knew it would be a region where the glaciers are located, but they didn't realize it was global in scope."
While there have been many studies that show the effects of melting ice sheets on uplift, Coulson and her coworkers looked at horizontal shifts and a larger area. The deformations can vary greatly from one year to the next.
Researchers found that horizontal movement can actually be greater than vertical movement in some areas. To measure crust movement in three dimensions, they used field measurements and satellite data from 2003 to 2018.
These crust rebounds can take thousands of years. However, the study points out that there have been some changes across the Earth's surface since the 11,000 year ago end of the last Ice Age.
Coulson says that Earth is an elastic structure on recent timescales. However, Earth behaves more like a fluid with a slow moving speed.
"Ice age processes can take a really, really, really long amount of time to work out. Therefore, we still see the effects of them today."
Researchers compare the effects of the icepack to a wooden board being pushed on water. When the board is removed and the weight is gone the liquid expands to fill in the space. The same thing happens with Earth's crust.
With the global rate of ice melting increasing, scientists need to be able to determine how it affects the Earth's surface. Even if these shifts are small each year.
This new study provides us with more detail than ever before about what's going on. It's not only useful for studying melting ice or shifting Earth's shape but also for other scientific fields.
Coulson says, "Understanding all the factors that cause movement in the crust is really important to a wide range Earth science problems."
"For example, in order to observe accurately tectonic movements and earthquake activity, it is necessary to be able separate this motion from modern-day ice mass loss."
Geophysical Research Letters published the research.