Arctic cryosphere and Milankovitch forcing of Great Basin paleoclimate.

Although Great Basin paleoclimate history has been examined for more than a century, the orbital-scale paleoclimate forcings remain poorly understood. Here we show - by a detailed phasing analysis of a well-dated stalagmite δ18O time series - that Great Basin paleoclimate is linearly related to, but lagged, the 23,000 yr precession cycle in northern hemisphere summer insolation by an average of 3240 years (-900 to 6600 yr range) over the last two glacial cycles. We interpret these lags as indicating that Great Basin climate is sensitive to and indirectly forced by changes in the cryosphere, as evidenced by fast and strong linkages to global ice volume and Arctic paleoclimate indicators. Mid-latitude atmospheric circulation was likely impacted by a northward shifted storm track and higher pressure over the region arising from decreased sea ice and snow cover. Because anthropogenic warming is expected to reduce northern hemisphere snow and ice cover, continued increase in atmospheric greenhouse gases is likely to result in warming and drying over coming centuries that will amplify a warming trend that began ~2400 years ago.