Climatic and hydrologic change associated with desiccation of the Aral Sea, Central Asia

The surface area of the Aral Sea has decreased by ;RegCM2 simulates the mean precipitation observed in central Asia well. A positive precipitation bias over the Aral Sea region has a negligible impact on the simulated water balance of the sea because on-lake precipitation is a very small component of the water budget. The lake model coupled to RegCM2 accurately simulates Aral Sea surface temperatures (SSTs), mid-winter ice fraction, and annual Aral Sea evaporation. The simulated evaporation is, however, greater than observed during summer and less than observed during winter.;Based on a series of experiments in which only the size of the Aral Sea was varied, we found that desiccation is an important source of the observed seasonal changes in SST and P-E. The simulated hydrologic changes are primarily a response to the reduction in lake depth resulting from desiccation. However, desiccation does not lead to a substantial reduction in annual P-E over the Aral Sea. By perturbing the meteorological boundary conditions used to drive the model, we also examined how large scale warming, driven by either enhanced greenhouse gases or natural climatic variability, may have influenced the water balance of the Aral Sea since 1960. Large scale warming is likely an important source of the observed change in annual P-E, but has little influence on the seasonal patterns of changes. Overall, the observed hydrologic changes since 1960 are best explained by a combination of climatic warming and reduction in size of the Aral Sea.