Climate Variability and Glacier Morphometry, British Columbia, Canada
1,2
1
Erik Schiefer and Brian Menounos
Natural Resources and Environmental Studies Institute and Geography Program, UNBC (menounos@unbc.ca)
2
Current address: Department of Geography, UBC (schiefer@geog.ubc.ca)
Climate data representing upper accumulation zone conditions were joined to the glacier database using the
maximum elevation vertex coordinates as a scale-free interpolation point for each glacier polygon within the BC
inventory. We use this appended data to describe climatic conditions at glacier headwalls for the two to three decade
period prior to the TRIM mapping. A small decrease in monthly temperatures and a large decrease in autumn-winter
precipitation are observed for increasingly continental glacier regions (Figure 3).
A) Hindcast temperature and precipitation variability during the Little Ice Age (LIA); and
B) Predict how glaciers will respond to future climate scenarios for the decade 2020.
600
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
E
500
400
300
200
DATA SOURCES
100
0
mm J F MA M J J A S O N D
600
1
2
Yukon
60°N
N.W.T 120°W
3
sk a
Alberta
Al a
Pacific
Ocean
130°W
ice
3000 m
Mass balance sites:
1 - Gulkana
2 - Wolverine
3 - Lemon Creek
4 - Peyto
5 - Place
6 - Helm
7 - Sentinel
8 - South Cascade
9 - Blue
0 m a.s.l
Long-term (>20 yr)
1 mass balance record
4
50°N
5
6
7
9
U.S.A
8
For our analyses, we utilized large-scale (1:20,000) digital
extents of ice cover and a 25 m digital elevation model
(DEM) for BC, both of which were produced from aerial
photography acquired during the mid 1980s (TRIM data Geographic Data BC, 2002). We developed an automated
procedure to identify glacier outlets based on relief
characteristics of the ice extent boundaries and applied a
flowshed algorithm to extract individual glacier
topographies (Schiefer et al., submitted). The resultant
inventory contains 12,031 glaciers distributed through all
the major mountain ranges of BC (Figure 1, Table 1).
Measures of glacier morphometry, including planimetric and
hypsometric parameters, were extracted and incorporated
within the glacier inventory.
Figure 1. Ice coverage for BC and monitored
glacier locations for the region (>20 year record).
Hypsometric shading shows extent and relief of
BC.
Table 1. BC glacier inventory summary by mountain region.
Region
Abr.
total
glacier % of
area TRIM
ice
(km2)
number with area
exceeding
total
number
of
glaciers
0.5
km2
5
km2
50
km2
max.
area
(km2)
max.
length
(km)
max.
relief
(km)
min.
elev.
(m)
St. Elias
E
2928
68
478
331
58
13
451
59b
2.5
171
North Coast
NC
8549
81
2983
2030
253
23
244
47
3.0
5d
Central Coast
CC
1937
80
1898
1288
25
0
19
13
1.7
351
South Coast
SC
7145
89
3183
2167
221
12
492a
51
3.6c
148
Insular
I
22
77
45
16
0
0
2
2
0.7
968
Skeena
S
618
86
565
345
15
0
15
9
1.2
1029
North Rockies
NR
432
87
388
244
7
0
24
13
1.5
1460
Central Rockies CR
335
79
218
147
14
0
16
9
1.7
1168
South Rockies
SR
1043
80
650
356
45
0
44
14
2.2
1106
Columbia
C
1998
85
1623
912
69
0
28
13
2.1
1206
totals: 25008
82
12031
7836
707
48
Prominent glaciers: aKlinaklini Glacier, bTweedsmuir Glacier, cFranklin Glacier, dGrand Pacific Glacier
Spatial interpolations combined with elevation adjustments have been developed for generating scale-free climate
normal data (1961-1990), including both mean monthly temperature and precipitation, for western Canada (Wang et
al., 2006). We find these procedures useful for compiling down-scaled climate data within the remote and
mountainous terrain of BC (Figure 2).
20°C
1350 mm
-8°C
15 mm
Figure 2. Examples
of monthly, scale-free
climate data extracted
for all of BC.
500
600
500
Mean Jan precipitation
S
400
300
200
100
0
mm J F MA M J J A S O N D
°C
°C
600
500
NC
400
300
200
100
0
mm J F MA M J J A S O N D
400
300
200
100
0
mm J F MA M J J A S O N D
500
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
CR
400
300
200
100
0
mm J F MA M J J A S O N D
°C
CC
400
300
200
100
0
mm
°C
600
600
500
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
NR
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
J F MA M J J A S O N D
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
600
°C
mm
500
Figure 3. Locations of
inventoried glaciers exceeding
5 km2 in area (color coded by
region listed in Table 1).
Climographs show mean
climatic conditions (1961-1990)
at glacier heads.
°C
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
SR
100
0
500
SC
400
300
200
100
0
mm
600
°C
mm
J F MA M J J A S O N D
500
J F MA M J J A S O N D
400
300
200
100
0
J F MA M J J A S O N D
B) N Coast-St Elias
Β
σ
Intercept
1410 13
Spr-Sum temp. -140 10
Aut-Win prec.
106 10
Percent slope
17
3
Glacier order
157 23
Shape index
192 26
2
n=326, Adj. R =0.72, σest=
P
***
***
***
*
**
**
282 m
.P<10
-3
*P<10
-6
**P<10
-9
***P<10
-12
0.6
0.4
0.2
0
Table 2. Change of monthly mean temperature
or precipitation (individually by season and region)
required to explain LIA maximum glacier reliefs.
B C
Region
A
B C
Region
Region
N
Spr-Sum temp.
Aut-Win precip.
S-C Coast (A)
323
-1.93 ± 0.16 °C
352 ± 25 mm
N Coast-St Elias (B)
249
-1.35 ± 0.14 °C
171 ± 19 mm
Columbia-Rocky (C)
109
-1.73 ± 0.17 °C
114 ± 14 mm
Research in the southern Coast and Rocky mountains
indicates that the majority of outermost LIA moraines were constructed during cooler conditions of the 1700s and early
1800s AD (Luckman and Wilson 2005; Koch et al., 2007). Our results suggest that the high elevation terrain of BC
experienced colder late LIA temperatures than has been reported for the extratropical Northern Hemisphere based on
tree ring widths (Cook et al., 2004). Our estimated temperature anomalie for the LIA maximum is similar to that
reported for the southern Rocky Mountains based on maximum latewood density records (Luckman and Wilson 2005).
The glacier-climate models can be similarly used to estimate potential equilibrium glacier reliefs for glaciers subject to
a modified climate regime. For BC mountain regions, ensemble GCM projections of mean monthly Mar-Aug
temperature and Sep-Feb precipitation for the 2020s generally range up to a 2°C increase in temperature and up to a
20 mm increase in precipitation (Barrow et al., 2004). The effect of increased glacier ablation by a 2°C increase in
Mar-Aug temperature greatly exceeds the increase of glacier accumulation caused by a 20 mm increase in Sep-Feb
precipitation (Table 3). Predicted reductions of glacier relief for a 2°C temperature increase range between 292 and
308 m for the South-Central Coast Mountains and between 313 and 356 m for the Columbia-Rocky Mountains
depending on the amount of precipitation change. These statistical models do not account for changing glacier slope,
morphometry, or head elevation. The temporal influence of these additional controls must be considered for a more
detailed or more long-range projection of future glacier conditions.
°C
We regress glacier extent - represented by relief, and measures of glacier morphometry - against seasonal climate
variables. Climate variables include mean monthly autumn-winter precipitation (dm) and spring-summer temperature
(°C), used as indices for ice accumulation and ablation respectively. Morphometric variables, used to account for
topographic controls on glacier relief, include surface slope (%), glacier order (analogous to stream order), and a
shape index of accumulation to ablation zone width. Glacier net mass balance records (Figure 1) reveal a slight
negative, average net mass balance for the 1961 to mid 1980s period (Figure 4). Our assumption that glaciers were in
a near steady-state condition is not entirely unreasonable, which is required to use glacier extent to infer climatic
conditions. Results for three amalgamated glacier regions are summarized below for glaciers >5 km2 in area. Glacier
relief is reduced by 140 to 178 m per degree increase in Mar-Aug monthly temperature and extended by 82 to 216 m
per decimeter increase in Sep-Feb monthly precipitation between regions. Relief is greater for steeper, higher order,
and more 'top-heavy' glaciers.
P
***
***
*
*
***
*
261 m
0.8
GCM-BASED PREDICTION
MODELING
A) S-C Coast
Β
σ
Intercept
1425 17
Spr-Sum temp. -154 11
Aut-Win prec.
82 14
Percent slope
16
3
Glacier order
244 26
Shape index
184 35
n=246, Adj. R2=0.70, σest=
1.0
°C
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
C
2
The models relating glacier relief to climatic and morphometric
variables can be used to infer potential climate conditions during the
LIA since former glacier extent can be reconstructed from terminal
moraines. We digitized the most downvalley LIA position for glaciers
which exhibited discernable end moraines from orthorectified,
Landsat imagery. LIA maximum glacier relief was estimated for those
positions using the TRIM topography (change in the uppermost
glacier elevation is assumed to be negligible). At the time of the
TRIM mapping, most glaciers had retreated ~2 km upvalley and
ascended ~200 m (Figure 5). Glaciers which coalesced with another
of comparable size at the LIA maximum were excluded from this
analysis because morphometric attributes may have been
significantly altered. Observed LIA glacier reliefs can be explained by
a Mar-Aug temperature decrease of between 1.35 to 1.93°C or a
Sep-Feb monthly mean precipitation increase of between 114 and
352 mm depending on region (Table 2).
Figure 5. Observed horizontal and vertical
changes in glacier termini between estimated
LIA max. position and TRIM glacier extent.
200
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
4
A
300
600
6
1.2
0
400
C) Columbia-Rocky
Β
σ
P
Intercept
1268 23 ***
Spr-Sum temp. -178 19 ***
.
Aut-Win prec.
216 49
Percent slope
18
4
*
.
Glacier order
134 32
.
Shape index
146 42
n=135, Adj. R2=0.69, σest= 166 m
Mean Jul temperature
15.0
10.0
5.0
0.0
-5.0
-10.0
-15.0
-20.0
-25.0
8
Distance of retreat since LIA max (km)
General circulation models (GCMs) predict that high elevations and high latitudes will experience large temperature
increases in this century. Existing and proposed networks of meteorological stations in western Canada are
inadequate to monitor these changes. Glacier fluctuations are a reliable and easily observed terrestrial indicator of
climate change (Paul et al., 2007). We compare contemporary climate fields of British Columbia (BC), Canada to
morphometric parameters of glaciers to develop statistical models that extract a climatic footprint from the glaciers.
The climate-glacier relations are subsequently used to:
LIA RECONSTRUCTION
Reduction of glacier relief since LIA max (km)
GLACIER CLIMATE
Table 3. Mean change in glacier relief by region for Spring-Summer temperature increases up to
2°C and Autumn-Winter monthly precipitation increases up to 20 mm.
Precipitation change
Temperature
change
INTRODUCTION
0 mm
10 mm
20 mm
0 mm
10 mm
20 mm
0 °C
0m
8m
16 m
1 °C
-154 m
-146 m
2 °C
-308 m
-300 m
0 °C
0m
11 m
21 m
-138 m
1 °C
-140 m
-129 m
-292 m
2 °C
-280 m
-269 m
S-C Coast
0 mm
10 mm
20 mm
0 °C
0m
22 m
43 m
-119 m
1 °C
-178 m
-156 m
-135 m
-259 m
2 °C
-356 m
-334 m
-313 m
N Coast-St Elias
Columbia-Rocky
Regression model results by region. Glacier relief (m)
is the dependent variable.
REFERENCES
3
2
Net balance (m)
1
Barrow E., Maxwell B., and Gachon P. 2004. Climate Variability and Change in Canada: Past,
Present and Future. ACSD Science Assessment Series No. 2, Meteorological Service of
Canada, Environment Canada.
1
Cook E.R., Esper J., and D’Arrigo R.D. 2004. Extra-tropical Northern Hemisphere land
temperature variability over the past 1000 years. Quaternary Sci. Rev., 23, 2063-2074.
0
Dyurgerov M. 2002. Glacier mass balance and regime measurements and analysis, 1945-2003,
edited by M. Meier and R. Armstrong. Institute of Arctic and Alpine Research, University of
Colorado.
-1
Geographic Data BC. 2002. British Columbia specifications and guidelines for geomatics,
release 2.0. Victoria, BC, Canada.
Koch J., Clague J.J., and Osborn G.D. 2007. Glacier fluctuations during the past millennium in
Garibaldi Provincial Park, southern Coast Mountains, British Columbia. Can. J. Earth Sci., 44,
1215-1233.
-2
-3
-4
1950
Individual net mass balance
Average net balance record
Average net balance ‘61-’85
1960
1970
1980
1990
2000
Year
Figure 4. Glacier mass balance records for monitoring
sites listed in Figure 1.
ACKNOWLEDGMENTS
This study was supported by a Canadian Foundation for
Climate and Atmospheric Sciences (CFCAS) grant
through the Western Canadian Cryospheric Network
(WC2N). We thank the BC Government for providing the
provincial TRIM and DEM data. Comments provided by
Dan Moore (Dept. of Geography - University of British
Columbia) and Luke Bornn (Dept. of Statistics University of British Columbia) helped guide our analyses
and are greatly appreciated.
Luckman B.H. and Wilson R.J.S. 2005. Summer temperatures in the Canadian Rockies during
the last millennium: a revised record. Clim. Dynam., 24, 131-144.
Paul F., Kääb A., and Haeberli W. 2007. Recent glacier changes in the Alps observed by
satellite: consequences for future monitoring strategies. Global Planet. Change, 56: 111-122.
Schiefer E., Menounos B., and Wheate R. 2007. Recent volume loss of British Columbian
glaciers, Canada. Geophys. Res. Lett., 34, L16503.
Schiefer E., Menounos B., and Wheate R. Submitted. A comprehensive inventory of glaciers
and glacier morphometry, British Columbia, Canada. J. Glaciol.
Wang T., Hamann A., Spittlehouse D. and Aitken S. N. 2006. Development of scale-free climate
data for western Canada for use in resource management. Int. J. Climatol., 26: 383-397.
WC2N
AGU 2007 Fall Meeting
Paper Number: GC41A-0094