Zonally symmetric changes in the strength and position of the Southern Westerlies drove atmospheric CO2 variations over the past 14 k.y.

Abstract

Terrestrial records from 41 to 52 degrees S across the Southern Hemisphere reveal nearly synchronous multimillennial trends in moisture derived from the Southern Westerly Winds (SWW) since 14 ka, pointing to a marked zonal symmetry in SWW changes across a broad swath of the southern middle latitudes. The data suggest a southward shift of the SWW that coincided with a rapid atmospheric CO2 rise starting ca. 12.5 ka, a widespread decline in SWW strength between ca. 10 and 7 ka contemporaneous with an similar to 8 ppm reversal in the deglacial atmospheric CO2 rise, followed by stronger SWW and a steady multimillennial increase in CO2 until the preindustrial maximum. We conclude that zonally symmetric changes in the intensity of the SWW at multimillennial time scales have covaried with atmospheric CO2 variations since 14 ka, and suggest that changes in the SWW-Southern Ocean coupled system have influenced the atmospheric CO2 concentration through wind-driven upwelling of CO2-rich deep waters in the high southern latitudes.