Palaeoclimate

Sun and wind

Geophys. Res. Lett. http://doi.org/jjf (2012)

Credit: © HEMERA/THINKSTOCK

An equatorward shift of the belt of westerly winds at southern mid-latitudes occurred during the prolonged solar minimum between AD 1645 and 1715, according to an analysis of model simulations and palaeoclimate records.

Vidya Varma of MARUM, University of Bremen, Germany, and colleagues used two transient climate model simulations to assess the effects of the Maunder Solar Minimum on atmospheric circulation, as well as calculating the effect of the reduced solar output on stratospheric ozone content. In the simulations, the solar minimum was associated with a weakening of the wind belt between 40° and 60° S, and a strengthening of winds to the north, linked to oceanographic changes. However, the equatorward shift was strongest in the simulation that included a reduction in stratospheric ozone concentrations, as would be expected from a reduced photolytic production of ozone in the upper atmosphere during solar minima.

A reconstruction of westerly wind intensity over the past millennium from marine sediments also supports a northward shift of the wind belt during prolonged periods of low solar output. The researchers attribute the shift to a combination of stratospheric changes and ocean and sea-ice dynamics.

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Newton, A. Sun and wind. Nature Geosci 5, 762 (2012). https://doi.org/10.1038/ngeo1631

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