Written by: Lisa Stelzner
Primary Source: Daily Dose of Science Blog
Parts of Antarctica have a very thick ice sheet (more than 2.6 miles thick), and you can imagine just how heavy that ice is. When the ice starts to melt and gets thinner, it causes the earth below it to rebound upward to counter for less weight being on top of it. This is called isostasy. You can think of a similar situation when you get up off a couch or mattress, and it springs back up to its normal height when there is no weight on it.
Rebound from ice sheets or glaciers that have retreated long ago tends to happen very slowly – less than a centimeter per year (and in fact, it is still happening in the Great Lakes region that was covered by the Laurentide Ice Sheet). However, GPS stations on Antarctica have found that land on the Antarctic Peninsula is rising by over 1.5 cm per year. Right next to the thinning ice sheets, there are no GPS stations, but the land could be rising by over 4 cm per year from model estimates. The amount of uplift that would take thousands of years has occurred in over a decade. This means the uplift witnessed must be from more than just isostasy. It turns out that the Earth’s mantle under Antarctica flows faster and is “runnier” (less viscous) than other parts of the mantle, and this can cause the mantle to push up the crust faster after an ice sheet retreats than normal.
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