ANNUAL BALANCE OF NORTH
CASCADE GLACIERS 1984-2005
CIRMOUNT 2006, Mount Hood, OR Mauri
S. Pelto, Environmental Science, Nichols
College, Dudley MA 01571
peltoms@nichols.edu
Why Measure Glacier
Mass Balance?
„
„
„
„
Mass balance is the dominant control
of future terminus behavior.
Annual mass balance is the best
measure of annual climate and its
impact on a glacier.
Mass balance Is viewed as one of the
most sensitive natural recorders of
climate by the IPCC.
Annual balance is what we determine
on North Cascade glaciers. This is the
mean net change in glacier thickness
measured on a fixed date each year. It
is reported as an average value of
snow or ice lost in meters of water
equivalent gained or lost. It is
determined at the end of the melt season.
Field Observation Program
„
„
„
„
Annual balance measured on 10
glaciers beginning in 1984.
Two glaciers Lewis and Spider
Glacier melted away in 1990 and
1995 respectively.
Emphasis is on high
measurement density and using
the same methods at the same
location on the same date each
year.
Repeat Longitudinal Profile
mapping on each glacier, to
provide an independent check on
cumulative mass balance change.
Lynch Glacier
Measurement
network: Each dot is a measurement
point.
Geographic characteristics of each
glacier.
GLACIER
ASPECT
AREA
ACCUMULATI
(km2)
ON1
TO DIVIDE
2
ELEVATION
(m)
Columbia
SSE
0.9
DS, DW, AV
15km west
1750-1450
Daniels
E
0.4
DS, WD
1km east
2230-1970
Easton
SSE
2.9
DS
75km west
2900-1700
Foss
NE
0.4
DS
At Divide
2100-1840
Ice Worm
SE
0.1
DS, AV
1 km East
2100-1900
Lower
S
0.8
DS,WD
West 55 km
1850-1460
Lyman
N
0.5
DS, AV
2 km East
2100-1850
Lynch
N
0.7
DS,WD
At Divide
2200-1950
Rainbow
ENE
1.6
DS,AV
70 km West
2040-1310
Curtis
SC
Yawning
N
0.3
DS
At Divide PC
2100-1880
Table 1. The geographic characteristics of the fourteen glaciers where annual balance has
been monitored annually. Accumulation sources: wind drifting = WD, avalanche
accumulation = AV, direct snowfall = DS.
Measurement of snow
accumulation: We rely on Probing
and Crevasse stratigraphy to
determine the thickness of the
residual snowpack layer from the
previous winter.
Probing relies on driving a probe
through the relatively soft snowpack
from the previous winter. The snow-firn
that survived the previous summer or
blue ice under that snow is much harder,
and cannot be penetrated. This
discontinuity provides a reliable point
measure of snow depth.
Measurements are made in August and
again at the end of the ablation season.
Crevasse Stratigraphy
„
Annual snowlayer
thickness is visible
much like tree rings.
providing a two
dimensional
measurement of
snowpack thickness
and thus is more
accurate than point
measurements from
probing or snowpits.
Only vertically walled
crevasses can be
used. The layer can be
traced from crevasse
to crevasse and
checked via probing.
The crevasse is a
natural incision
through the snow layer
versus an artificial one
provided by snowpits
or probes.
Crevasse Stratigraphic :
The
annual layers provide a two dimensional
view of the annual layer.
Ablation is measured by emplacing
stakes into the glacier and measuring
the change in height above the glacier
surface on several occasions each
summer.
Glacier Annual Mass
Balance
„
„
„
Annual balance of North Cascade glaciers
strongly correlated from glacier to glacier,
annual range averages approximately 1m.
Mean annual balance from 1984-2005 has
been –0.52 m/a.
The cumulative mass balance thickness
loss of 12.5 m represents a 20-40% loss of
glacier volume.
The annual balance records indicate the high
degree of correlation between nine North
Cascade glaciers including South Cascade
Glacier observed by the USGS
N o r t h C ascad e G lacier A nnual B alance
3
2
C o lumb ia
D aniels
1
F o ss
Ice W o r m
0
Lo wer C ur t is
Lynch
-1
R ainb o w
-2
Y aw ning
-3
East o n
So ut h C ascad e
-4
Year
Cross Correlation Coefficients of annual
mass balance
Columbia
Daniels
Foss
Ice Worm
Lower Curtis
Lynch
Rainbow
Yawning
Easton
South Cascade
Mean
Correlation
Col
1
0.85
0.9
0.86
0.93
0.86
0.94
0.92
0.93
0.83
Dan
0.85
1
0.95
0.95
0.93
0.96
0.92
0.95
0.98
0.97
Foss
0.9
0.95
1
0.93
0.95
0.98
0.95
0.97
0.98
0.78
IW
0.86
0.95
0.93
1
0.93
0.91
0.92
0.9
0.97
0.84
LC
0.93
0.93
0.95
0.93
1
0.94
0.97
0.97
0.97
0.78
Lyn
0.86
0.96
0.98
0.91
0.94
1
0.94
0.97
0.97
0.75
Rain Yawn East SC
0.94 0.92 0.93 0.84
0.92 0.95 0.98 0.97
0.95 0.97 0.98 0.78
0.92 0.9 0.97 0.84
0.97 0.97 0.97 0.78
0.94 0.97 0.97 0.75
1 0.95 0.99 0.76
0.95
1 0.99 0.81
0.99 0.99 1 0.94
0.76 0.81 0.94
1
0.9 0.95 0.94 0.92 0.94 0.93 0.93 0.94 0.97 0.85
Cumulative annual balance of
North Cascade glaciers 19842005
North Cascade Glacier Cumulative Annual Balance
2
0
-2
-4
-6
-8
-10
-12
-14
Years
Lower Curtis Glacier:
An avalanche
fed cirque glacier that has a southern orientation.
ALPI-Annual Balance
6
5
4
3
ALPI
2
1
ALPI
0
-1
-2
-3
-4
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
Annual Balance
ENSO- Annual Balance
1.50
1.00
ENSO
0.50
ENSO Annual
0.00
-0.50
-1.00
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
Annual Balance
PDO-Annual Balance
2
1.5
PDO
1
0.5
Series1
0
-0.5
-1
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
Annual Balance
0.50
1.00
1.50
2.00
Forecasting rules:
Rule 1. If both PDO and MEI are positive, than glacier
mass balance will be negative. This rule works in all
14 years it is applicable.
Rule 2. If PDO is negative and MEI is equilibrium or
negative, mass balance will be equilibrium or positive.
This rule is successful in 13 of 15 years.
Rule 3. If PDO is positive and MEI is neutral the
glaciers will have an equilibrium or negative balance.
The rule is correct in 4 of 5 years.
Rule 4. If PDO is negative and MEI is positive the
glacier balance will be negative. This is true in 5 of 6
years
Rule 5. If PDO is positive and MEI is negative glacier
mass balance will be negative. This rule provides an
accurate result in 3 of 4 years.
Table 4. The mean value of winter PDOW
(October-April) and winter MEIW (OctoberApril). Glacier mass balance from South
Cascade Glacier 1960-1986, combined South
Cascade and NCGCP data 1987-2005 (bn). The
relative phase: positive, >0.2 (p), negative, <-0.2
(n) and equilibrium -0.2 to -0.2 (e), for PDOW,
MEIW indices and glacier annual balance.
Year
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
PDOW
0.34
0.30
-1.64
-0.62
-0.83
-0.63
-0.42
-0.73
-0.54
-0.74
0.78
-1.44
-1.56
-0.27
-1.10
-0.45
-1.40
1.05
0.34
-0.16
0.70
0.87
0.31
0.87
1.38
0.73
0.91
1.78
1.23
-0.52
-0.30
-1.37
0.40
0.66
1.05
-0.50
0.59
0.28
1.30
-0.58
-1.16
-0.04
-0.67
1.51
0.54
0.39
MEIW
-0.17
-0.23
-0.79
-0.71
0.41
-0.64
1.06
-0.52
-0.68
0.54
0.34
-1.38
-0.74
1.41
-1.70
-0.85
-1.55
0.49
0.81
0.29
0.75
0.15
-0.07
2.68
-0.07
-0.45
-0.15
1.29
0.98
-1.16
0.26
0.33
1.61
0.80
0.52
0.99
-0.48
-0.20
2.46
-0.93
-0.95
-0.48
-0.05
0.91
0.34
0.65
bn
-0.5
-1.1
0.2
-1.3
1.2
-0.17
-1.03
-0.63
0.01
-0.73
-1.2
0.6
1.43
-1.04
1.02
-0.05
0.95
-1.3
-0.38
-1.56
-1.02
-0.84
0.08
-0.77
0.12
-1.2
-0.71
-2.56
-1.64
-0.71
-0.73
-0.2
-2.03
-1.23
-1.6
-0.69
0.1
0.63
-1.86
1.02
0.38
-1.57
0.55
-1.1
-1.7
-2.9
PDOW
p
p
n
n
n
n
n
n
n
n
p
n
n
n
n
n
n
p
p
e
p
p
p
p
p
p
p
p
p
n
n
n
p
p
p
n
p
p
p
n
n
e
n
p
p
p
MEIW
e
n
n
n
p
n
p
n
n
p
p
n
n
p
n
n
n
p
p
p
p
e
e
p
e
n
e
p
p
n
p
e
p
p
p
p
n
n
p
n
n
n
e
p
p
p
bn
n
n
p
n
p
e
n
n
e
n
n
p
p
n
p
e
p
n
n
n
n
n
e
n
p
n
e
n
n
n
n
p
n
n
n
n
e
p
n
p
p
n
p
n
n
n
Rule#
3
5
2
2
4
2
4
2
2
4
1
2
2
4
2
2
2
1
1
NA
1
3
3
1
3
5
3
1
1
2
4
2
1
1
1
4
5
5
1
2
2
NA
2
1
1
1
Result
yes
yes
yes
no
no
yes
yes
no
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
NA
yes
yes
yes
yes
no
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
no
yes
yes
yes
NA
yes
yes
yes
yes
Accumulation zone of
Columbia Glacier, August 2005
Easton Glacier
„
The largest glacier observed, extending from
1600 to 2900 m.
Columbia Glacier Negative balance
in 2005
„
The lowest glacier with the terminus at 1415 m
and the head of the glacier at 1700 m. It is
heavily avalanche fed.
Columbia Glacier positive mass
balance 2002
Conclusions
„
„
„
The mean annual balance of
-.41 m
has led to an average mass loss of 8.5
m and thinning of 9.5 m.
Recent annual balance have shown
exceptional interannual variability and
an increasingly negative trend.
PDO, ENSO and ALPI are poorly
correlated with annual balance
statistically. However, as predictors
based on principal mode they are in
certain situations good predictors.
For example they point to negative
balances in 2005.