CGRG Bibliography of Canadian Geomorphology
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Author : Freymueller, J.T.; Larsen, C.F.; Motyka, R.J.; Sato, T.; Miura, S. and Sun, W.
Date : 2011.
Title : Glacial isostatic adjustment in Alaska and British Columbia.
Publication : American Geophysical Union (AGU) Fall Meeting 2011. December 5-9, 2011. San Francisco, California. USA.
Issue : C34A-03.
Page(s) :
Abstract
The glaciers and icefields of coastal Alaska and British Columbia have lost an enormous amount of ice since the end of the Little Ice Age (LIA), with the collapse of the Glacier Bay Icefield alone equivalent to 8 mm of global sea level rise. Rapid mass wastage continues today, and both the total mass loss and present rates are generally well constrained. We have studied the mass changes and the Earth’s response to it through a combination of glacial history observations, dating of raised shorelines, small aircraft laser altimetry, DEM differencing, permanent and temporary tide gauge data, GPS, and relative and absolute gravity change. Our observations show that extreme uplift in southeast Alaska began about 1770 AD, with relative sea level (RSL) change as large as 5.7 m, and rapid present-day uplift. We observe uplift rates >30 mm/yr in two regions, Glacier Bay and the area of the Yakutat Icefields, and regional uplift rates >10 mm/yr over a large area. Tide gauge records show that rapid uplift has persisted for decades. One site near Harlequin Lake, SE of Yakutat, has uplifted >80 mm/yr over the last two years due to extreme localized ice mass wastage. The known ice load history explains the present day uplift and gravity change rates well, given an Earth model consisting of an elastic lithosphere with a thickness of 54 (45–65) km over a low viscosity asthenosphere 110 km thick and a higher viscosity upper mantle. The upper mantle viscosity is assumed from larger-scale studies because the scale of the ice load is not small enough to make models sensitive to this value. The best estimate for asthenosphere viscosity is 6 (4.0–12.0) * 10^18 Pa-s, which is quite similar to the value estimated from postseismic deformation studies 800 km to the west in the region of the 1964 Prince William Sound earthquake.
Bibliography of Canadian Geomorphology