The world's oceans are rising. Over the past century, they're up an
average of about eight inches. But the seas are rising more in some
places than others. And scientists are now finding that how much sea
level rises in, say, New York City, has a lot to do with exactly where
the ice is melting.
A warming climate is melting a lot of glaciers and ice sheets on land. That means more water rolling down into the oceans.
But the oceans are not like a bathtub. The water doesn't rise uniformly.
To understand why, think of the earth as a spinning top. When huge ice sheets — some are two miles thick — start to melt, it actually affects the Earth's rotation.
"What happens is when you change the mass of the ice," explains Eric Larour, who studies the frozen parts of the planet, "the modification itself makes the wobble change, and this in turn changes the shape of the ocean on the Earth."
When the wobble shifts, the oceans shift as a whole, as if you were shaking a mound of Jello at the Thanksgiving table.
That's part of the story, but something else happens too.
Many ice sheets and glaciers are so massive, they produce a significant gravitational field, almost as if they were small versions of the moon. The force is tiny, but it does attract nearby ocean water.
"So what happens when the ice melts," says Larour, "is that there is less of it, so the ocean recedes away from the mass of ice."
https://www.npr.org/2017/11/24/566280048/the-sea-level-threat-to-cities-depends-on-where-the-ice-melts-not-just-how-fast
A warming climate is melting a lot of glaciers and ice sheets on land. That means more water rolling down into the oceans.
But the oceans are not like a bathtub. The water doesn't rise uniformly.
To understand why, think of the earth as a spinning top. When huge ice sheets — some are two miles thick — start to melt, it actually affects the Earth's rotation.
"What happens is when you change the mass of the ice," explains Eric Larour, who studies the frozen parts of the planet, "the modification itself makes the wobble change, and this in turn changes the shape of the ocean on the Earth."
When the wobble shifts, the oceans shift as a whole, as if you were shaking a mound of Jello at the Thanksgiving table.
That's part of the story, but something else happens too.
Many ice sheets and glaciers are so massive, they produce a significant gravitational field, almost as if they were small versions of the moon. The force is tiny, but it does attract nearby ocean water.
"So what happens when the ice melts," says Larour, "is that there is less of it, so the ocean recedes away from the mass of ice."
https://www.npr.org/2017/11/24/566280048/the-sea-level-threat-to-cities-depends-on-where-the-ice-melts-not-just-how-fast
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