Earth’s iron heart can melt, plus Atlantic weather and more ice thinning in this week’s news

Deep ocean jets drive Atlantic weather Regular weather patterns in the tropical Atlantic are driven by deep ocean currents, not the winds and other atmospheric factors that cause El Ni±o and similar cycles. An international research team now finds evidence that 4.5-year cycles in temperature, precipitation and winds are driven by deep jets in equatorial waters that carry energy upward. These fast-paced currents appear to originate “in the abyss (perhaps as deep as several thousand meters),” the researchers report online May 19 in Nature , and vary independently of the seasons. — Janet Raloff Arctic ice still thinning Year-old ice floating on the Beaufort Sea is 20 to 30 centimeters thinner this year than in the last two, new aircraft- and satellite-based analyses find. On May 6, researchers from the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, completed a six-week stint flying the polar skies from Alaska to Norway with a host of sensors. An electromagnetic ice-thickness gauge, towed 15 meters above the sea surface, found that Beaufort ice north of Alaska and Canada was 1.4 meters thick. That’s 18 percent thinner than in 2009, meaning the ice probably will not survive this coming summer, concludes AWI’s Stefan Hendricks. — Janet Raloff Core meltdown Even the Earth’s inner iron heart can be coaxed to melt. A team of scientists based in England, India and the United States has calculated how heat flows around the boundary between the innermost core, which is solid iron, and the outer core, which is liquid. The simulations suggest that heat transferred from shallower in the Earth can sometimes get all the way down to the inner core, melting it in places. The work, which appears in the May 19 Nature , helps explain the existence of a long-puzzling layer 150 kilometers above the inner-core boundary, and sheds light on how the fluid outer core generates Earth’s magnetic field. — Alexandra Witze

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