Juan M Lora , Daniel Enrique Ibarra 

While the climate evolution of North America during the last deglaciation has received considerable attention, few detailed model–data comparisons of the deglacial hydroclimate have been conducted at the continental scale. Here we use a transient climate simulation of the last deglaciation and a synthesis of hydroclimate proxies from across the continent to broadly assess the moisture budget and its evolution, including the primary components and mechanisms for changes, and evaluate the level of agreement between model and data in order to inform areas of major discrepancy for attention in future work. At the broadest scale, the simulation indicates that North America was wetter than modern through much of the last deglaciation, with the exception of the Pacific Northwest. This was principally due to increased moisture convergence by the mean flow over the west of the continent, and by transient eddies over the east. We find that the simulation demonstrates considerable skill in comparison to proxy records in the coastal Southwest and Pacific Northwest, with limited success in other regions. The highest disagreement occurs in the North-central region, where the model and data disagree on the sign of changes. In addition, we find that the areas of agreement coincide with regions whose hydroclimate is dominated by winter precipitation. In addition, regions of disagreement are those where summer precipitation is predominant, and where the model suggests dynamical changes are important. These results illustrate the impact of the ice sheet on the atmospheric dynamics, and therefore the importance of its accurate reconstruction, as well as that of model resolution. Our analysis and synthesis provide context for future transient climate simulations, and suggest numerous areas of priority for future research.