190 Quaternary Geology and Geomorphology (Posters)

Tuesday, 18 October 2005
1:30 PM - 5:30 PM

DENDROGLACIOLOGICAL LITTLE ICE AGE ADVANCE HISTORY OF THE LAND LOBE GLACIER, SOUTHCENTRAL ALASKA

Paper number: 190-11
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

Tree-ring dating a collection of 30 logs and over 170 tree cores from 20 sites including 9 new sites, provides calendar dates and significantly updates previous tree-ring studies at the Land Lobe Glacier, a distributary land-terminating glacier from Columbia Bay, Southcentral Alaska. New data shows the Land Lobe Glacier, which is now retreating, advanced near its ice margin as early as AD 1777 and scaled up a major bedrock knob over a distance of less than 0.5 km in just over 90 years. The glacier reached its Little Ice Age (LIA) terminal position between 1857 and 1869 AD. These dates are constrained by spectacularly preserved forests from the recently deglaciated forefield that were killed or damaged by the advancing ice. The glacier remained near its LIA maximum until the retreat of the neighboring iceberg-calving Columbia Glacier captured much of the Land Lobe's drainage area initiating its stagnation and retreat.

Extensive sampling in 2005 along a flowline recovered multiple logs and cores with outer growth rings preserved. Average advance rates for the Land Lobe of approximately 5 meters per year are significantly less than the 20-40 m/yr. rates of the Columbia Glacier determined from similar dendroglaciological evidence. Based on a rate of 5 m/yr the Land Lobe would have taken 1500 years to advance from its confluence with Columbia Glacier to its terminal LIA position.