Icebergs Contribute to Sea Level Rise

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When you learned about Archimedes back in elementary school, your teacher probably told you that a floating object displaces an amount of water equal to its own weight. Although an ice cube pokes up out of the water, when it melts, the level of the water should stay the same. Extrapolate this concept to an iceberg floating in the ocean—a bigger version of the ice cube in your water glass—and you would think that melting icebergs shouldn't contribute to sea level rise. Well, you'd be wrong, say geoscientists at the University of Leeds.

In their study, published this week in Geophysical Research Letters, the researchers used satellite observations and a computer model to assess the impacts of melting icebergs. The total amount of floating ice that is turned into ocean water each year is equivalent to 1.5 million Titanic-sized icebergs. Due to differences in the temperature and density of the ice and water (the seawater is warmer and saltier than the icebergs that float in it), when the icebergs melt, the resulting ocean water is 2.6 percent greater in volume than the volume of water that the iceberg had displaced.

Calculated out, the ocean rises by about 49 micrometers each year due to melting icebergs. That's not a lot of sea level rise—sea level globally is rising by about 3 millimeters (or 3,000 micrometers) per year—but the scientists say it deserves monitoring.

Elsewhere in news of rising sea levels, Slate profiles an EPA scientist who warns that beaches on the Eastern seaboard are in danger of disappearing. Is it time to abandon beachfront property?

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