Exploring U.S. drought dynamics using proxies and models in paleoclimate data assimilation

Abstract:

Drought is a topic of vital importance to the western United States, with implications for society and terrestrial ecosystems. To explore drought variations prior to the relatively short instrumental record, we utilize a data assimilation methodology which combines information from proxy data and model output to reconstruct past climate, allowing us to analyze drought over the past millennium. In this data assimilation framework, annually-resolved proxy records provide location-specific information and climate model output quantifies relationships in the climate system, allowing us to create an annually-resolved multivariate climate reconstruction -- the “Last Millennium Reanalysis”. Analysis of this climate reconstruction reveals a significant connection between interannual U.S. drought and the El Niño-Southern Oscillation, as discussed in earlier work, but this connection appears to explain only a small portion of the reconstructed drought variability. Drought in the eastern and central U.S. may also be affected by variations in Atlantic sea surface temperatures, but most drought variability is not easily connected to the primary modes of SST variability. This suggests that intrinsic atmospheric dynamics play a large role in shaping much U.S. drought variability.