Columbia Glacier, Alaska: Changes in velocity 1977–1986

Abstract

The Columbia Glacier, a grounded, iceberg-calving tidewater glacier near Valdez, Alaska, began to retreat about 1977. Drastic retreat occurred in 1984, and by early 1986, retreat amounted to 2 km. The glacier has thinned more than 100 m since 1974 at a point 4 km behind the 1974 terminus position. Between 1977 and 1985 the lower glacier ice velocity increased from 3-8 m/d to 10-15 m/d. Ice velocity in the region 0.5 km above the terminus was highest near the time the glacier was most receded (late fall), and lowest near the time of maximum length (early summer), for years 1977-1982. Velocity in the region 52-57 from the head of the glacier was highest in mid-spring, and lowest in early fall from 1977 to 1985. Through the years 1983-1985, the dates of maximum and minimum velocities within 0.5 km of the receding terminus tended toward the dates of the 52-57 km maximum and minimums. This occurred because as the terminus receded, it was no longer strongly influenced by the reverse slope of the terminal moraine shoal. Velocities near the terminus fluctuated by 2-3 m/d during summer and fall, when liquid water input was variable, and were relatively constant during winter. Hourly variations in ice velocities are controlled by liquid water input to the glacier hydraulic system and tide stage. Velocity increases near periods of high surface water input and decreases during periods of high tide as a result of hydrostatic back pressure.

Short-term variations in calving of a tidewater glacier: LeConte Glacier, Alaska, U.S.A.

“…On Columbia Glacier, this seasonal pattern has been attributed to seasonal variations in speed, with a 3 month lag between maximum speed and maximum length (Krimmel and Vaughn, 1987;Krimmel, 2001). On LeConte Glacier, where ice influx is nominally constant, this is not the case.…”

Short-period observations of speed, strain and seismicity on Ice Stream B, Antarctica

“…A correlation between marine tides and strain would suggest that tide was affecting the basal water pressure and therefore the flow of the ice stream. A tidal effect on speed was observed on Columbia Glacier, Alaska (Krimmel and Vaughn, 1987;WaIters and Dunlap, 1987) . Also, we found a good correlation between tide and speed on lower J akobshavns Isbne, Greenland (Echelmeyer and Harrison, 1989) .…”

A preliminary forecast of the advance of Hubbard Glacier and its influence on Russell Fiord, Alaska

“…Seasonal changes observed on Columbia Glacier have included minor advances during late winter or early spring and terminal retreats during fall (Krimmel and Vaughn, 1987). Changes in the terminus position of Hubbard Glacier are recorded by field surveys, time-lapse photography ( fig.…”