View article

Global hydroclimate significantly differed from modern climate during the mid-Holocene (6 ka) and Last Glacial Maximum (21 ka). Consequently, both periods have been described as either a partial or reverse analogue for current climate change. To reconstruct past hydroclimate, an offline paleoclimate data assimilation methodology is applied to a dataset of 130 lake status records which provide relative estimates of water level measured using percentile units. The proxy observations are integrated with the climate dynamics of two transient simulations (TraCE-21ka and HadCM3) using a multivariate proxy system model (PSM) which estimates relative lake status from available climate simulation variables. The resulting DAMP-21ka (Data Assimilation of Moisture Patterns 21,000–0 BP) reanalysis reconstructs annual lake status and precipitation values at 500-year resolution and represents the first application of the methodology to global hydroclimate on timescales spanning the Holocene and longer. Validation using Pearson’s correlation coefficients indicates that the reconstruction (0.33) is more skillful, on average, than model simulations (0.10), particularly in portions of North America and East Africa where data density is high and proxy-model disagreement is prominent during the Holocene. Results of the PSM and assimilation are used to evaluate climatic controls on lake status, spatiotemporal patterns of moisture variability, and proxy-model disagreement. During the mid-Holocene, wetter conditions are reconstructed for North and East Africa, Asia, and southern Australia, but, in contrast to the model prior, negative anomalies are observed …