Taku Glacier, Southeast Alaska, U.S.A.: Late Holocene History of a Tidewater Glacier

Abstract

Taku Glacier is the largest glacier draining the Juneau Icefield, and reaches tidewater near the mouth of the Taku River. Taku Glacier historically calved icebergs into a 100-m-deep tidal basin but presently terminates on its shoal moraine and outwash apron. Radiocarbon dates, dendrochronology, and investigations of lateral moraines indicate that five major cycles of growth and recession of Taku Glacier occurred during the last 3000 yr. The timing of advances and retreats between 3000 and 2000 yr ago appear asynchronous with nearby glaciers. Those between 2000 and 100 yr ago generally coincide with land-terminating Juneau Icefield glaciers, suggesting these events were driven by changes in glacier mass balance caused by regional climatic fluctuations. However, a retreat of Taku Glacier ca. 1650 yr BP preceded retreats at nearby glaciers by about 200 yr. In addition, since 1890 Taku Glacier has advanced 7.3 km, during a period when virtually all nearby land-terminating glaciers have been retreating. The history of Taku Glacier shows that the behavior of tidewater glaciers can reflect climatic changes occurring over sustained periods of time (>100 yr), but that intrinsic dynamic instabilities may cause retreats and advances unrelated to climate shifts.