As ice caps melt, Earth’s rotation is slowing down, and that’s making our days ever so slightly longer. Shrinking glaciers are affecting both the rotation rate and axial tilt of the Earth, by redistributing all that once-frozen water around the world. As water shifts from poles toward the equator, our planet’s midsection is becoming a wee bit wider. And that extra girth is causing the Earth to brake—in the same way that a spinning skater can slow herself down by sticking her arms out.
http://gizmodo.com/the-bizarre-reason-earths-rotation-will-slow-down-this-1747632959