Title: Centennial-Scale Shifts in the Position of the Southern Hemisphere Westerly Wind Belt Over the Past Millennium
Author: Koffman, B.G., Kreutz, K.J., Breton, D.J., Kane, E., Winski, D., Birkel, S.D., Kurbatov, A. and Handley, M.
Periodical: American Geophysical Union, Fall Meeting 2013, abstract #PP31D-1892

The Southern Hemisphere (SH) westerly winds are a major driver of regional and global climate, yet their behavior on decadal to centennial timescales during the late Holocene remains poorly understood. 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. In addition, we present automatic weather station and ERA-Interim reanalysis data in order to characterize local and regional-scale atmospheric circulation. We use correlations with reanalysis zonal wind speed to calibrate the dust size distribution record over the period 1979-2002, finding significant positive interannual relationships (r = 0.3-0.5, p < 0.1). Using our coarse particle percentage record (defined as number of particles mL-1 [4.5-15]/[1-15] µm diameter *100), and through comparison with spatially distributed climate reconstructions from the 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.) in response to high-latitude SH cooling and a contraction of the SH Hadley cell.

Year: 2013