Centennial-scale shifts in the position of the Southern Hemisphere westerly wind belt over the past millennium

Abstract

Abstract. We present the first high-resolution (sub-annual) dust particle dataset from West Antarctica, developed from the West Antarctic Ice Sheet (WAIS) Divide deep ice core (79.468° S, 112.086° W), and use it to reconstruct past atmospheric circulation. We find a background dust flux of ∼4 mg m−2 yr−1 and a mode particle size of 5–8 μm diameter. Through comparison with other Antarctic ice core particle records, we observe that coastal and lower-elevation sites have higher dust fluxes and coarser particle size distributions (PSDs) than sites on the East Antarctic plateau, suggesting input from local dust sources at lower elevations and sites closer to the coast. In order to explore the use of the WAIS Divide dust PSD as a proxy for past atmospheric circulation, we make quantitative comparisons between mid-latitude zonal wind speed and the dust size (coarse particle percentage, CPP) record, finding significant positive interannual relationships. Using our CPP record, and through comparison with spatially distributed climate reconstructions from the Southern Hemisphere (SH) middle and high latitudes, we infer latitudinal shifts in the position of the SH westerly wind belt during the Medieval Climate Anomaly (MCA; ∼950–1350 C.E.) and Little Ice Age (LIA; ∼1400–1850 C.E.) climate intervals. We suggest that the SH westerlies occupied a more southerly position during the MCA, and shifted equatorward at the onset of the LIA (∼ 1430 C.E.) due to cooler surface temperatures and a contraction of the SH Hadley cell.