Recent paleoclimate proxy records developed from minerals precipitated in California caves suggest that the central Sierra Nevada foothills experienced large variations in precipitation during the last deglaciation, including an increase in precipitation coincident with the Younger Dryas cold period (~12.9 to 11.5 ka). From 16.5 to 8.6 ka, isotopic and geochemical proxies from the Moaning Cave stalagmite indicate drier and possibly warmer conditions during Northern Hemisphere warm periods and wetter and possibly colder conditions during Northern Hemisphere cool periods. Linkages between northern high-latitude climate and precipitation in the Sierra Nevada suggested here imply that, under conditions of continued global warming, this drought-prone region may experience a reduction in Pacific-sourced moisture.

To better understand these variations, we use a transient simulation of the climate evolution from the Last Glacial Maximum (21,000 years ago) to the early Holocene (10,000 years ago) with the coupled atmosphere-ocean general circulation model, the Community Climate System Model version 3 (CCSM3). With realistic time-varying boundary conditions and forcings, the model successfully simulates the deglacial climate evolution of the North Atlantic region, including the collapse of North Atlantic Deep Water. The transient simulations were originally made using a low resolution version of the model but to better resolve details about California, selected time period restarts were regridded to a higher resolution and rerun for short time slices. This provides additional details necessary to compare with the proxy data.