Westerly wind shifts drove Southern Hemisphere mid-latitude peat growth since the last glacial

Extratropical peatlands in the Southern Hemisphere preserve detailed information on climatic and environmental change going back millennia. They are particularly valuable for understanding the evolution of the mid-latitude southern westerly winds (SWW), which play a major role in driving regional temperature and precipitation patterns, Antarctic sea-ice extent and ocean carbon fluxes. Here we investigate the timing and drivers of peatland initiation across the southern mid-latitudes after the Last Glacial Maximum (21,000 years ago) and test how this might relate to past changes in the SWW. We radiocarbon-date basal peats from the Falkland Islands and collate published basal peat radiocarbon ages from peat-forming regions south of 35° S. Using kernel density estimate models, we find distinct latitudinal phases of post-glacial peat initiation that suggest that peat growth is sensitive to variations in SWW position through their influence on moisture availability, temperature and dust deposition. A peak in peat growth in regions north of 52.5° S during the Antarctic Cold Reversal (14,700–12,800 years ago) suggests an equatorward migration of the SWW, coinciding with a slowdown in atmospheric CO₂ increases. In light of recent SWW intensification and poleward migration, our findings highlight the potential for ongoing changes in the Southern Hemisphere climate and carbon fluxes under continued anthropogenic heating.