TREE RING EVIDENCE FOR A MEDIEVAL WARM PERIOD IN COLUMBIA BAY, ALASKA

Recent dendroclimatic compilations from Northern Hemisphere temperature-sensitive tree-ring sites support a Medieval Warm Period (MWP) spanning parts of the 8th through 12th centuries AD. A newly-compiled, well-replicated ring-width chronology from Columbia Bay is a record of temperature variation along the maritime southern Alaskan coast and now spans the MWP (AD 774-2000). Over the past two decades the tidewater Columbia Glacier has experienced catastrophic retreat exposing almost 15 km of fjord. The ring-width record here is assembled from living trees and subfossil wood killed by a steady, millennium long glacial advance of the iceberg calving Columbia Glacier margin.

Preliminary dendroclimatic results using Regional Curve Standardization (RCS) techniques to extract a low-frequency climate signal suggest that the multiple decades centered on AD 1050 were warmer relative to the following centuries spanning the Little Ice Age. This warming is consistent with the reconstructed glacial record for the region that shows retracted ice margins during this time.