Evolution of moisture transport to the western U.S. during the last deglaciation

We investigate climate dynamics and teleconnections governing moisture transport to the western U.S. during past warm and cool intervals of the last deglaciation using paleoclimate simulations of the Bølling warm (∼14 ka) and Younger Dryas cool (∼12 ka) events. Results suggest that the waning continental ice sheet weakened atmospheric pressure centers in the region leading to a progression from a more sinuous to more zonal Pacific winter storm track throughout the deglaciation. Furthermore, variations in meltwater flux to the Atlantic influenced the meridional temperature gradient over the Pacific and thereby modulated storm track intensity. Changing sinuosity of the storm track may be reflected in broad increases in modeled δ¹⁸O_precip and observed δ¹⁸O_speleothem values from the western U.S. over the last deglaciation, whereas abrupt δ¹⁸O_speleothem shifts are dynamically consistent with the response of storm track intensity to variations in meltwater flux to the Atlantic.