Left panel: A copy of the upper panel of Figure 1 in B2008. It represents linear regression of Δp after the original measurement from three Antarctic stations at mlat >83° S was grouped according to the IMF B_y. Middle panel: Reproduction of the linear regression method using ΔZ_g at ~mlat >70° S. Error bars are plus/minus one standard-error-in-the-mean. Right panel: Scatter plot and linear regression for the ΔZ_g data without the initial five-bin grouping. The upper panel of Figure 1 in B2008 is reproduced with permission from John Wiley and Sons.