Runoff from irrigation has moved so much water from land to sea that Earth’s rotation might have measurably shifted.
Computer simulations suggest that from 1993 through 2010, irrigation alone nudged the North Pole by about 78 centimeters, researchers reported in the June 28 Geophysical Research Letters. That would make irrigation the second largest contributor to polar drift after the ongoing rebound of Earth’s surface following the retreat of glaciers since the last ice age.
Researchers have long known that the North Pole wanders across the Arctic seascape in a circle a few meters in diameter. Seasonal weather patterns cause part of this cyclical drift, and long-term variations in the temperature and salinity of ocean water help drive a 14-month-long oscillation dubbed the Chandler wobble (SN: 4/15/03).
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