EXTENDING THE TREE RING RECORD AND GLACIER CHRONOLOGY FOR THE COLUMBIA GLACIER, ALASKA

Tree-ring and radiocarbon chronologies from the retreating margin of the Columbia Glacier, Alaska sampled in 2005 CE showed the margin of the tidewater glacier was advancing at this location about 1050 CE. Since 2005 the tidewater margin has split and retreated an additional 6 km. Overrun wood recovered from this newly exposed land will add additional tree-ring dates to the more than 300 dates on logs from the Bay that reveal a millennium-long advance followed by the dramatic, ongoing retreat initiated in ~1980 CE and now that totals more than 20 km.

The timing of the tree-ring dated glacier chronology from Columbia Bay is consistent with tidewater glacier cycle as put forth by Austin Post and others, in part based on observations at Columbia Glacier. Samples from the buried forests that have now emerged from beneath the glacier will extend the ring-width tree ring chronology and will modify the current tree-ring based reconstructions for the region. Ongoing research intends to investigate the possibility of divergence occurring during the Medieval Warm Period (MWP) about ~ 1000 CE. In addition to building on the past database these newly discovered and dated tree-rings will allow further research on the nature and variability of the Medieval Warm Period and perhaps offer insights into why this tidewater glacier was advancing during the MWP.