Mid- to late Holocene centennial-scale shifts of the Southern Hemisphere Westerly winds

Centennial-timescale variability of the Southern Hemisphere Westerly wind belt (SHW) is poorly documented, mainly due to a paucity of long, high-resolution climate records from the Southern Hemisphere. Moreover, the role played by the Southern Annular Mode (SAM), El Niño Southern Oscillation (ENSO) and solar variability in controlling the SHW is not well understood. We present a 7000-year record of grain size end-member modelling and C/N from Lake Lanalhue at 38°S in central Chile as a reconstruction of variations in precipitation and the position of the northern margin of the SHW. Centennial-scale drier/wetter conditions in central Chile were coeval not only with drier/wetter and cooler/warmer conditions in southern Chile, but also with more/less extensive sea ice and cooler/warmer conditions in the Ross Sea, stronger/weaker winds in the Amundsen Sea, and equatorward/poleward shifted SHW in the southwestern Atlantic Ocean. Taken together this indicates centennial-scale variations resembling positive/negative phases of the Southern Annular Mode (SAM + /SAM – ). Drier/wetter conditions were also related to more/less El Niño conditions. Therefore, we suggest that SHW variability in central Chile at a centennial-timescale was related to the ENSO-SAM phasing, i.e. El Niño/SAM + during drier periods and La Niña/SAM – during wetter periods, and ultimately controlled by solar variability, with increased/decreased insolation forcing shifts towards a SAM + /SAM – -like state.