CLIMATE VARIABILITY IN NORTH AMERICA DURING THE FIRST MILLENNIUM AD AND POSSIBLE LINKS TO THE MIDDLE-LATE WOODLAND TRANSITION IN THE MIDWEST

Climate proxy records from coastal and near coastal sites along the North Pacific and ocean records along the California coast indicate that the interval spanning AD 400 through 800 had large variations in temperature with decades centered on AD 600 as possibly the coldest in the past two thousand years. The strong linkage between the North Pacific and the Midwest via the Pacific North American teleconnection pattern (PNA) offers a means to climatically compare the two regions.

Decreased sea surface temperatures in the Pacific have been implicated in forcing sustained drought in North America; significant cooling may also lead to an expansion of the polar front, which reroutes moisture laden air masses. Paleohydrometeorological indicators suggest that some parts of North America has experienced more severe droughts and wet periods during the first millennium AD than in recent centuries. Dendroclimatic evidence from the Midwest show sustained dry periods between AD 600 and 700 and radiocarbon-dated alluvial sequences suggest increased alluviation during this time possibly forced by larger moisture variability leading to landscape instability. Lake and tree-ring records from surrounding regions show variously increased moisture or drought.

This broad interval spanning AD 400 through 800 coincides with the transition from the Middle Woodland to Late Woodland periods, which is characterized by the Hopewell to Mississippian shift in cultures. Here we assess the hypothesis that climate change had an impact on the cultural shift by compiling paleoclimate records for key regions in North America and comparing them with the Archaeological record through the first millennium AD.