Movement of Antarctic Icebergs Helped Drive the Onset of Ice Ages

Nature, January 13

Ice ages have long been associated with small periodic changes in the Earth’s orbit around the sun, but how and why such changes could trigger an ice age has remained an enigma.  Now, one possible explanation has arisen: under a specific orbital setting, Antarctic icebergs travel, and melt further and further away from Antarctica. This has made the Southern Ocean saltier, while the Atlantic Ocean became fresher. This large shift in freshwater distribution causes large-scale changes in ocean currents and circulation, with the result that global oceans absorb larger amounts of CO2, decreasing atmospheric concentrations and reducing global mean temperature, triggering an ice age. For the past 1.6 million years, ice ages have always been preceded by the same conditions. Today, although Antarctica is calving icebergs more than ever before, the rapid warming of the Southern Ocean would likely prevent this specific feedback mechanism, as icebergs melt primarily within the Southern Ocean; and modeling instead tends to predict feedbacks that would speed up ice sheet loss on Antarctica instead.

https://www.nature.com/articles/s41586-020-03094-7

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