World o' lakes

NASA/GSFC/MODIS Rapid Response Team, Jeff Schmaltz

World o' lakes

Eat your heart out, Minnesota. Your license plates boast of 10,000 lakes, but even that’s only a small fraction of the world’s total of about 117 million. Using software to scan approximately 8500 cloud-free Landsat images captured between 1997 and 2003, researchers were able to reliably detect lakes big—such as North America’s Great Lakes, shown, which together contain about 18% of the world’s unfrozen fresh water—and small—down to those covering about 2000 square meters, an area almost the size of two Olympic swimming pools. Excluding Central Asia’s Caspian Sea, the world’s largest enclosed body of water, Earth’s lakes collectively cover about 5 million square kilometers—about 3.7% of the planet’s land area not currently smothered by the ice sheets of Antarctica and Greenland, the researchers report online before print in Geophysical Research Letters. The new census, the first survey of satellite images to count lakes so small, will help scientists better estimate the amount of carbon stored in lake-bottom sediments, as well as the amounts of carbon dioxide and methane released into the atmosphere from lake waters each year, the researchers say.

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