EXTENDED RECORDS OF PAST CLIMATE FROM EASTERN NORTH AMERICAN TREE-RINGS

We are developing a network of drought-sensitive tree-ring chronologies from eastern North America, derived primarily from two species of long-lived conifer, eastern red cedar (Juniperus virginiana) and northern white cedar (Thuja occidentalis). Aside from the spatially restricted bald cypress (Taxodium distichum), these two species represent the best opportunity for developing a network of climate-sensitive tree-ring records that cover the past 500-1000 years for the eastern US. The first chronologies from this project have been incorporated into a tree-ring network used by Cook et al. (1999) to reconstruct drought across North America, thus allowing for the extension of the reconstructions back to AD 1500 or earlier in regions where it was not previously possible to do so. Paleoclimatic perspective on drought is vital to understanding the nature and causes of drought, especially the severe multi-year events. Our Cedar Knob chronology from West Virginia, for example, gives the rare opportunity to look at tree-growth/climate relationships over the past 1500 years. Notably, there are periods of low frequency variability suggestive of the Medieval Warm Period and Little Ice Age, respectively. We have also developed chronologies from Wisconsin, New Hampshire, Pennsylvania, and Virginia that span from 500 to 1000 years, extended through the use of "sub-fossil" wood in the form of standing-dead stems and downed and buried logs. We have identified sites in Maine, Vermont, Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Kentucky and North Carolina where old cedar trees have either been reported or where terrain types match criteria developed for this project. In this paper we discuss the current status of the network, and explore the spatiotemporal characteristics of climate and drought across the eastern US for the past 500 years and more. We explore the regional expression of climate anomalies such as drought through time, and analyze decadal to multi-centennial variability suggestive of Medieval Warm Period (MWP) and Little Ice Age (LIA) type signatures.

References Cook, E.R., Meko, D.M., Stahle, D.W., and Cleaveland, M.K. 1999. Drought reconstructions for the continental United States. Journal of Climate 12:1145-1162.