Simulations by CCSM4 support our hypothesized linkages, as the projected future climate changes depict a seasonally varying circulation response hinging on the enhanced warming and resulting geopotential height increases aloft in the Arctic. During boreal autumn and winter, sea ice loss leads to upper-air height increases mainly over the Arctic Ocean with compensating decreases over mid-latitudes, which reduces the poleward gradient. During spring and summer, however, the band of maximum anomalous ridging shifts southward over high-latitude land. This behavior resembles the upper-air circulation changes induced by prescribed reductions in sea ice and snow cover in previous versions of the model. The associated seasonal changes in mid-tropospheric zonal winds exhibit a nearly symmetrical reduction in mid-latitude westerlies in all seasons, suggesting a combination of weaker winds and perhaps a poleward shift in the flow. Weaker zonal winds slow the eastward progression of planetary waves, favoring more persistent weather conditions, thermal isolation of mid-latitude continents, and thus greater seasonality superimposed on an overall warming world. During summer, changes in upper-air geopotential heights are expected to act synergistically with projected reductions in soil moisture in middle latitudes to foster more frequent and intense heat waves and droughts. During winter a slowing and meridional elongation of planetary waves caused by Arctic Amplification favors cold-air outbreaks over the continents, thereby tempering the greenhouse-forced decline in extreme cold events and favoring regionally alternating snowy patterns and abnormal winter warmth that vary from year to year.