Atmospheric simulations of southern South America's climate since the Last Glacial maximum

This study investigates the simulated present and past climate of southern South America through the use of the PSU/NCAR MM5 mesoscale model forced by Princeton GFDL global atmosphere-ocean model data. This approach is taken to obtain climate data with sufficiently high resolution to resolve the steep mountain ranges of the southern Andes, which generate large amounts of orographic precipitation. Results indicated that the region experienced northward shifted low level westerlies at and before 9000 years before present and shifts in upper level winds associated with the midlatitude jet culminated about 9000 years ago. A simple energy balance model indicates that the lower equilibrium line altitudes in the southern Andes during the Last Glacial maximum persisted into the early Holocene, resulting in an expansion of the area receiving net snow accumulation, particularly in eastern parts of the Andes mountains. Changes in simulated winds and precipitation in the lee of the southern Andes are consistent with Laguna Potrok Aike climate proxies.