Southward shifts and enhancements of the westerlies over the Tibetan Plateau during North Atlantic cooling events.

Variations in mid-latitude westerlies have an important influence on climate change, but their impact on the Tibetan Plateau (TP) since the Last Glacial Maximum is still debated, due to shortage of direct proxies reflecting the variations in the westerlies. Here we present an exotic (Cedrus) pollen record from the interior of the TP since 26.5 cal ka BP to reconstruct the changes in westerlies. Combined with its modern distribution, the Cedrus pollen in our record is considered to reflect the change in the intensity and position of the westerlies. Increased Cedrus pollen inputs are consistent with cooling phases during the Heinrich Stadial (HS) 2, HS 1a, HS 1c and Younger Dryas, suggesting that the westerlies were abruptly enhanced and southward-shifted, which can be attributed to the increased equator-to-pole temperature gradients and sea ice advance. Our record over the TP is in agreement with other reconstructions from the lower altitudes suggests a synchronous change in the westerlies at different levels. • A direct proxy for variations in the westerlies over the Tibetan Plateau was presented. • We reconstructed the variations in the westerlies since the LGM. • The Cedrus pollen record was a direct evidence for variations in the mid-upper westerlies. [ABSTRACT FROM AUTHOR]