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Greenland and Antarctica are home to most of the world's glacial ice

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that accumulates on land– including its only two ice sheets.

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That’s why scientists focus their energy here first

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when looking for answers about sea level rise.

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Here’s a concerning reality:

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Combined, the two regions contain enough ice,

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that if it were to melt all at once,

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sea levels would increase by nearly 215 feet.

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Rising Waters: Out-of-Balance Ice Sheets

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Now, that isn’t going to happen anytime soon,

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but even a few feet of sea level rise (much less 215)

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would be disastrous for the planet’s coastal communities.

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For most people, these processes are happening so far away

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that’s hard to imagine how melting at the poles even occurs.

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Let’s lay some groundwork:

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A healthy glacier is one that accumulates the same amount of snowfall and it loses.

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It’s a system in balance.

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Unfortunately, today’s glaciers and ice sheets are not in balance.

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Here’s what that actually looks like:

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In Greenland, when warm summer air melts the surface of a glacier,

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the meltwater drills holes down through the ice.

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It makes its way down to the bottom of the glacier

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where it runs between the ice and the bedrock,

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and eventually shoots out in a plume at the base of the glacier.

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The meltwater plume is lighter because it doesn't contain salt

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– it’s freshwater.

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It rises toward the surface,

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mixing warm, salty ocean water upward in the process.

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The warm water then rubs up against the bottom of the glacier,

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causing even more of the glacier to melt.

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This often leads to calving,

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where ice cracks and breaks off into large icebergs.

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In addition to melting caused by warm air and a warm ocean,

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Antarctica faces another challenge: the bedrock itself.

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Researches often split Antarctica into two regions: east and west.

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Unlike East Antarctica, the bedrock that makes up West Antarctica

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is below sea level, which means it’s actually underwater.

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Warmer water has an easier time seeping in between the continental shelf

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and the ice sheet, melting the ice from below.

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This causes the ice shelves to thin and break off into the ocean.

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Melting and ice loss have accelerated at both poles in recent years.

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The more we learn about this complicated process,

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the more accurately we'll be able to predict sea level rise far into the future.

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