Evidence of the Younger Dryas in Central America

Three sites provide records that address whether the Younger Dryas was manifest in Central America. Marine records from Barbados and the Cariaco Basin an discussed, as well as possible climatic forcing mechanisms. Sequences from montane La Chonta Bog, Costa Rica, and lowland Lake Quexil, Guatemala, record a temperature decline of 1.5-2.5 degrees C dated between 11,070-10,400 C-14 years BP and ca. 12,000-10,300 C-14 years BP, respectively. The record from Lake La Yeguada, Panama, does not include cooling, although significant reorganization of local a communities occurred during the Younger Dryas chronozone. Colder tropical SSTs throughout deglaciation contributed to sub-regional climatic variation, more intense monsoonal activity, and cooler air temperatures. However, the temperature reversals are not associated with the coldest tropical SSTs which occurred during meltwater pulses. The temperature reversals appear to be a response to extra-tropical conditions, presumably in the North Atlantic, which suggests that Younger Dryas cooling extended as far south as Costa Rica. In Panama, monsoonal conditions may have blocked cooler temperatures. Precipitation continued to increase throughout deglaciation due to strong forcing by seasonal solar insolation in Central America while desiccation events occurred to the north and south.