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DATA OBSERVATIONS
Mass Balance
The annual balance record shows a markedly positive trend from 1946–1988 period. The mean
annual balance for the 42-year period is 0.42 m/a, representing a total thickening of 17.5 m w.e or
20 m in total ice thickness. From 1988–2005 mass balance changed significantly and has been
slightly negative averaging –0.17 m/a, a 3 m w.e. loss, or 3.3 meters of glacier thickness change
(Figure 2). A comparison of surface height change along Profile 4 from 1993–2004 and mean
surface balance yield –3.5 m and –2.7 m respectively. The next task in this research program is to
determine the height changes at survey location along additional profiles over an extended period,
thus providing additional surface balance data each year.
m we
20
18
16
14
12
10
8
6
4
2
0
-2
1946
1949
1952
1955
1958
1961
Juneau Icefield Mass Balance
Taku Cumulative bn Taku bn
1964
1967
1970
1973
1976
Year
Figure 2. Annual and cumulative mass balance of the Taku Glacier 1946–2005.
With the distribution of annual balance more accurately mapped in the lower neve section of the
glacier based on the 1998, 2003 and 2004 combined snowpit and probing measurements, mean
annual surface flux was determined both for the glacier region above Profile 4 and Profile 7,
summing the products of the area observed between each 0.2 m mass balance interval and the
annual balance for that interval. The surface flux accumulating above at Profile 4 was calculated to
be 5.5 × 10 8 m 3 a –1 , and 1.90 × 10 8 m 3 a –1 above Profile 7.
256
1979
1982
1985
1988
1991
1994
1997
2000
2003
2
1.5
1
0.5
0
-0.5
-1
-1.5