Attribution of Last Glacial Maximum precipitation change in Northern Hemisphere monsoon and arid regions

Abstract

Based on reconstructions from geological records, the precipitation during the Last Glacial Maximum (LGM) was markedly different from that of the preindustrial (PI) period. Especially in the terrestrial monsoon regions and arid regions of the Northern Hemisphere (hereafter referred to as NHTMR and NHTAR, respectively), the precipitation is more sensitive to changes in boundary conditions. However, the relative contributions of individual LGM forcings to precipitation in NHTMR and in NHTAR are still unclear. In this study, a series of climate model experiments were carried out to evaluate their contributions. The results showed that, compared with the PI period, the precipitation and area of NHTMR were both reduced in the LGM. In NHTAR, the precipitation was significantly reduced, but there was an increase in total area. Sensitivity experiments demonstrated that a decrease in sea surface temperature and an expansion of the ice sheet were the two principal contributors to lessening NHTMR precipitation, while the decrease in precipitation in NHTAR can be mainly attributed to ice-sheet-induced albedo and topography changes. Comparatively, the ice-sheet albedo effect had a greater impact on precipitation change than the topographic effect. The atmospheric circulation anomalies associated with the individual forcings were the underlying dynamic mechanism that drive the precipitation changes.