8. A Day Is Now How Long?

The melting of all the ice in Antarctica would have complex and interconnected effects on Earth’s systems, making it difficult to predict exactly what would happen. However, researchers do know that this event would affect the length of a day. The Earth’s rotation, as measured by satellites and astronomical methods, has undergone modest but noticeable changes due to the melting glaciers and the influx of meltwater into the oceans.

This “polar wander” process is driven by a lot of different factors—and climate change is one. “Because glaciers are at high latitudes, when they melt, they redistribute water from these high latitudes toward lower latitudes,” Harvard University geophysicist Jerry Mitrovica told Reuters in 2015. “Like a figure skater who moves his or her arms away from their body, this acts to slow the rotation rate of the Earth.”

Thus, when the ice melts and its water shifts across the globe, that causes Earth to spin noticeably faster or slower. As in Mitrovica’s example, it becomes like a figure skater who changes their weight and spin speed by lifting and lowering their arms while spinning on the ice.

As this ice-melting process has been going for decades in earnest, the length of a day has already increased by thousandths of a second. It is unclear how much longer the day would become if all of Antarctica’s ice were to melt, but it could be extremely measurable. Some recent estimates suggest the day could change by as much as 20 seconds in the next few years—and possibly significantly more after that.^[3]

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