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NASA is keeping a watchful eye on Greenland, tracking changes in the thick sheet of ice that covers most of the island.

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Why? Well, for the same reason that coal miners used to bring canaries into the coal mines.

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If they stopped singing, it was a warning sign that trouble was coming.

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Greenland's ice sheet is one of Earth's canaries when it comes to global warming.

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Polar regions are more sensitive to a warming Earth than other parts of the world,

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so what happens in places like Greenland, the rest of the Arctic, and Antarctica alerts us to what's in store for the rest of the planet.

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And Greenland's ice can also affect many of us directly.

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You see, Greenland has more land ice than any other place except Antarctica.

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If it all melted, it would raise sea level around 23 feet.

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That's enough to put coastlines throughout the world underwater.

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And in fact, the ice is melting.

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It's far from all gone. That could take centuries.

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But Greenland's ice sheet currently adds about 250 gigatons of water to the ocean every year.

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What's a gigaton? It's a billion tons, which is approximately a block of ice one kilometer square.

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And 250 of these giant Greenland ice blocks melt every year.

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All this extra fresh water from this melting ice could also change circulation patterns in the ocean and in the atmosphere.

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Which means, even if you don't live near the ocean, a melting Greenland could potentially affect your local weather in the future.

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So that's why NASA is monitoring Greenland's ice sheet.

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It's like that canary in the coal mine warning us of trouble.

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By tracking and measuring the changes, we'll all be better prepared for the future.

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NASA Jet Propulsion Laboratory, California Institute of Technology