The deglaciation of the mountains of Mexico and Central America

Abstract

The last deglaciation is an interval of marked changes in the climate system. The records of glaciation of tropical mountains offer unique opportunities to assess the timing of changes and the sensitivity of tropical climates to global and regional atmospheric phenomena. Here we summarize the existing knowledge on the glacial history of the highest mountains of the Trans Mexican Volcanic Belt (19.5°N) and Central America (Cuchumatanes in Guatemala, 15.5°N; Cerro Chirripó in Costa Rica, 9.5°N), focusing on the transition from the last local glacial maximum (LLGM) to the early Holocene, with some emphasis on records supported by cosmogenic nuclide dating. The LLGM in the mountains of Mexico (20-14 ka) and Central America (~21-18 ka) overlaps with the final part of the global Last Glacial Maximum (26.5-19 ka). A depression of the equilibrium line altitude (ELA) of glaciers of 1500-1000 m with respect to modern values is indicative of 9-6°C cooling. Deglaciation in Costa Rica started by 18 ka, while in Mexico glaciers remained at or near their maximum position until ~15 ka, probably due to the influence of Heinrich event 1. Glacier retreat commenced at 15-14 ka in central Mexico and accelerated from 14 to 13 ka, in coincidence with the Bølling-Allerød warming. A standstill or advance took place from 13 to 10.5 ka in Mexico. In Costa Rica, undated moraines formed between 18 and 10 ka. Full deglaciation across the region is recorded at ~10 ka, except on the mountains of central Mexico >4,200 m, and can be explained by a rise of the ELA of 300 to 450 m (warming of ~2-3°C) relative to the LLGM. In general, the deglacial records of central Mexico and Central America seem to be controlled by temperature. However, the temporal pattern of deglaciation of Costa Rica is similar to that of the northern tropical Andes, while the one from central Mexico is in agreement with the chronology of the western USA.