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The sheet of ice that covers Greenland

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contains enough frozen water to raise oceans by 25 feet

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across the globe

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As the planet warms, glaciers melt

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causing sea levels to rise

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But not all of that melt happens at the surface

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In the summertime, rivers and pools of meltwater

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find their way down through the glacier

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to the bed below.

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From there, the water runs beneath the glacier

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until it reaches the ocean.

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Because meltwater contains no salt,

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it weighs less than ocean water

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and rises up the front of the glacier

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in what scientists call a plume.

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Around Greenland, oceans are cold and fresh near the surface

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and warm and salty at depth

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As the plume rises, it draws in the warm, salty water

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metling the glacier face from the bottom up.

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Eventually, a piece of the glacier breaks off

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making an iceberg in a process known as calving.

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As the oceans warm,

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calving speeds up, causing glaciers to retreat

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and flow faster.

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Faster glaciers dump more ice into the oceans

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and drive sea levels higher across the globe.

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