A Moisture Balance Reconstruction for the Drainage Basin of Albemarle Sound, North Carolina

Abstract

Freshwater discharge into Albemarle Sound and many other large estuaries can have a major impact on the physical and biological properties of the estuary. Earlywood (EW) and latewood (LW) width tree ring chronologies recently developed from ancient trees and sub-fossil logs found at Devil's Gut of the Roanoke River, North Carolina, were used with new EW and LW width data from Blackwater River, Virginia, to reconstruct the July Palmer Hydrological Drought Index (PHDI) over the drainage basin of Albemarle Sound from 934 to 2005. This reconstruction is based on a principal component regression using millennium-long chronologies of both EW and LW widths, calibrated and verified against instrumental July PHDI from 1895 to 1985. The reconstruction provides a lengthy representation of inter-annual to multi-decadal growing season moisture variability that directly affects water quality in the Albemarle Sound estuarine ecosystem. Single-year drought and wetness extremes were more common in the modern instrumental period (1895-2005), but prolonged droughts reconstructed during the Medieval and Early Colonial eras were more severe and sustained than the reconstructed or observed droughts during the twentieth century. Several abrupt transitions between decadal drought and wetness regimes are reconstructed, especially during the Medieval Era. Composite analysis of lower-magnitude sub-decadal regime shifts in the instrumental record during the twentieth century indicates that major changes in mid-latitude circulation over the Northern Hemisphere may have been involved in these longer decadal transitions between moisture regimes over Albemarle Sound in prehistory. © 2013 Coastal and Estuarine Research Federation.

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Estuaries and Coasts

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