HR: 0830h
AN: C11C-0847    [PDF]
TI: Taku Glacier: Proglacial Deformation and Subglacial Erosion
AU: * Kuriger, E M
EM: ekuriger@gi.alaska.edu
AF: Geophysical Institute University of Alaska Fairbanks, 903 Koyukuk Dr, Fairbanks, AK 99775-7320 United States
AU: Motyka, R J
EM: jfrjm@uas.alaska.edu
AF: Geophysical Institute University of Alaska Fairbanks, 903 Koyukuk Dr, Fairbanks, AK 99775-7320 United States
AU: Truffer, M
EM: truffer@gi.alaska.edu
AF: Geophysical Institute University of Alaska Fairbanks, 903 Koyukuk Dr, Fairbanks, AK 99775-7320 United States
AU: Bucki, A K
EM: akbucki@gi.alaska.edu
AF: Geophysical Institute University of Alaska Fairbanks, 903 Koyukuk Dr, Fairbanks, AK 99775-7320 United States
AB: Taku Glacier has advanced about 7~km since 1890 and is continuing its advance today. Located in southeastern Alaska, this glacier flows from the Juneau Ice Field down to sea level. In the last several decades the glacier has bulldozed a berm of marine and fluvial sediments from the fjord bottom; this berm now separates the terminus from tidewater. The force of the advancing glacier is causing large-scale deformation within these sediments. In 2001, a series of thrust scarps began to form in front of a 200~m section of the terminus. These scarps were active for several months and produced a series of bulges that grew to be several meters in height above the surrounding sediments. Ground penetrating radar (GPR) was used to image the internal structure of these bulges. A trench dug into one of the proglacial ridges revealed that a $>$2~m clay/sand layer might have played an important role as a thrust zone during deformation. This layer could also be identified in the GPR returns.\\ Beside these scarp-formed bulges there are numerous indicators of the continued advance. Push moraines along the terminus range in height from 1~m to a towering 10~m. In some areas the advancing ice has dug into the sediments and has lifted the vegetation from below. We also observed up to 1~m thick debris freeze-on layers that, when exposed at the terminus, melt and contribute to the development of some moraines.\\ In addition to these observations we performed a series of radio echo-soundings over a grid that extends about 5~km upglacier. These data are compared with depth measurements made in 1989. Since then the glacier has advanced about 180~m. Within 1~km of the present terminus the glacier has deepened its bed by about 15~m, which indicates an erosion rate of about 1~my$^{-1}$ in this area. This rate agrees with the one observed over the past 100~years. Entrenchment plays an important role in the glacier's dynamics and needs to be taken into account when measuring volume changes.
DE: 1824 Geomorphology (1625)
DE: 1827 Glaciology (1863)
SC: Cryosphere [C]
MN: 2003 Fall Meeting