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2019-12-14. How Monsoons in Africa Drove Glacier Growth in Europe.

posted Jan 5, 2019, 2:28 PM by Alan Gould   [ updated Jan 5, 2019, 2:29 PM ]
By Emily Underwood, Eos/AGU/Geophysical Research Letters. [https://eos.org/research-spotlights/how-monsoons-in-africa-drove-glacier-growth-in-europe] For GSS A New World View chapter 1. Excerpt: A new study shows that low-latitude weather can affect distant glaciers. Around 250,000 years ago, most of North America and northern Europe was covered in glaciers. These massive ice sheets formed over thousands of years and waxed and waned in response to a long list of factors, including wobbles in Earth’s orbit, alterations in the atmosphere, and changing ocean currents. Now, scientists have added another mechanism to that list: distant monsoons. ...During a frigid period of the late Quaternary, large chunks of the European Ice Sheet melted and refroze, temporarily creating large, warm pools of meltwater in the Bay of Biscay, the gulf between Spain and France.  ...distant, low-latitude weather events such as the East Asian monsoon⁠ can impact glaciers far away, at much higher latitudes. To test whether monsoons could explain the European Ice Sheet’s ebb and flow, Kaboth-Bahr et al. examined cores of sediment extracted from the deep seafloor near the Strait of Gibraltar, as well as two other locations. Using the ratio of light to heavy minerals in the sediment as a proxy for the volume and force of water flow at the seafloor, they reconstructed ancient ocean currents dating back 250,000 years. ...when monsoons periodically weakened in northeast Africa, thus drying up the Nile River, the change caused saltier water to rush out of the Mediterranean Sea through the Strait of Gibraltar and into the Atlantic. As this relatively warm, salty water hit the Atlantic, it produced what is known as the Azores Current, a branch of the Gulf Stream that drags warm Atlantic waters toward England and northern Europe. During glacial periods, the pooling of this warm Atlantic water generates the moisture that makes ice sheets grow....