Download Increasing Variability of River Discharge in Northern Canada

Global Warming and its Effect on Snow/Ice/Glaciers
Encyclopedia of Snow, Ice and Glaciers
V. P. Singh, P. Singh, and U. K. Haritashya (eds.)
Springer
Stephen J. Déry
Environmental Science and Engineering Program
University of Northern British Columbia
3333 University Way
Prince George, BC, Canada, V2N 4Z9
E-mail: [email protected]
Tel: + 1 250 960 5193
Fax: + 1250 960 5845
2
2
GLOBAL WARMING AND ITS EFFECT ON SNOW/ICE/
GLACIERS
3
Synonyms
4
Impact of climate change on the cryosphere
5
Definition
6
7
8
Global warming. Rising air temperatures on a global scale.
Global warming and its effect on snow/ice/glaciers. Rising air temperatures on a global scale
that are modifying components of the cryosphere, including snow, ice and glaciers.
9
Introduction
1
10
11
12
13
14
15
16
17
18
19
20
One of the most notable manifestations of global warming is its impact on snow, ice and
glaciers. The cryosphere, defined as the portion of the earth system where water, soils, and
other natural materials occur in the frozen form, is a prominent indicator and integrator of
climate change as a contraction in its spatial extent, volume, and duration is particularly
sensitive to rising air temperatures. Components of the cryosphere such as snow, ice, and
glaciers play a major role in the global climate system through their distinct characteristics
such as their high albedo values that induce strong positive feedbacks on warming (Déry and
Brown, 2007) and their insulating properties that decouple the atmosphere with the
underlying land surface or water (Stieglitz et al., 2003). Further, the cryosphere forms
important and reliable reservoirs of freshwater, contributing water resources to a large
fraction of the global population (Barnett et al., 2005).
21
Observational Evidence of Change
22
23
24
25
26
27
28
29
30
31
32
33
There is mounting observational evidence that global warming is leading to modifications in
the state of the cryosphere. For instance, Déry and Brown (2007) report a 5% decline in snow
cover extent in the Northern Hemisphere between 1972 and 2006 based on satellite
measurements. Brown (2000) reconstructs the snow cover extent data prior to the satellite era
and finds a decreasing trend in Northern Hemisphere snow cover extent over the period
1915-1997. Brown and Braaten (1998) and Curtis et al. (1998) find declining snow depths
across most of Canada and Alaska during the 20th century. Mote et al. (2005) document a
widespread decline in snow mass in the North American Cordillera from 1925 to 2000 in
response to rising surface air temperatures. Ye et al. (1998) report decreasing (increasing)
snow depths in the zonal band 50-60oN (60-70oN) in Eurasia from 1936 to 1983. Stone et al.
(2002) document a 20th century trend toward earlier snowmelt in Alaska whereas Ye and
Ellison (2003) and Vaganov et al. (1999) observe an opposite trend in northern Eurasia.
34
35
Global warming also influences the different forms of ice found in oceans, lakes or rivers.
Observational records point to later freezing (trend of 5.8 days per century) and earlier
3
36
37
38
39
40
41
42
43
44
45
breakup (trend of 6.5 days per century) of lake and river ice across the Northern Hemisphere
from 1846 to 1995 (Magnuson et al., 2000). Sea ice in the Arctic declined in extent by about
3% per decade whereas sea ice in the Antarctic increased spatially by 1.3% per decade over
1978-1996 (Cavalieri et al., 1997). This observed asymetric response of sea ice extent to
global warming is consistent with global climate model (GCM) simulations. The annual
minimum in Arctic sea ice extent, typically reached in mid-September, attained an
unprecedented low value of 4.2 × 106 km2 in 2007 (Maslanik et al., 2007). The rapid retreat
in Arctic sea ice is outpacing all of the scenarios predicted by GCMs (Stroeve et al., 2007).
Submarine measurements reveal a 42% decline in Arctic sea ice draft thickness over a period
of 40 years ending in the 1990s (Rothrock et al., 1999).
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
In response to rising air temperatures and changing precipitation regimes, glaciers worldwide
are experiencing a general trend toward negative mass balances (Dyurgerov and Meier, 2000;
Oerlemans, 2005). Regional declines in glacier extent and volume include the Rockies and
Coast Mountains of North America, the Andes of South America, the European Alps and the
Asian Himalayas. Glaciers are particularly sensitive to changes in summertime air
temperatures that drive ablation and wintertime precipitation that forms accumulation. Strong
modifications in either of these seasonal quantities may alter the mass budget of glaciers.
Discharge of ice from outlet glaciers of Greenland doubled in the period 1996-2005 (Rignot
and Kanagaratnam, 2006) while surface melt and ablation expanded to record levels in
response to global warming (Tedesco et al., 2008). In the Southern Hemisphere, global
warming has not affected the overall mass balance of the Antarctic ice sheet owing in part to
its colder environment than the Greenland ice sheet. However, the collapse of the Larsen ice
shelf near the Antarctic Peninsula in January 1995 along with the subsequent acceleration of
ice discharge and calving provide some evidence of a growing importance of climate change
in the area (Rott et al., 1996; Rignot et al., 2004).
61
Future projections
62
63
64
65
66
67
68
69
70
71
72
73
74
75
A number of studies have examined the impacts of global warming on the potential future
state of the cryosphere. In general, simulations of 21st century climate by GCMs project
decreases in the spatial extent, volume and duration of many components of the cryosphere.
Frei and Gong (2005) and Déry and Wood (2006) project declines in the extent and duration
of the Northern Hemisphere snow cover. Räisänen (2008) and Déry and Wood (2006) also
report potential reductions in the seasonal accumulation of snow, particularly in the midlatitudes whereas high-Arctic regions may experience increases in seasonal snow mass.
Simulations of the future state of the global climate system project abrupt declines in sea ice
extent and thickness, with the potential of an ice free Arctic Ocean by the middle of the 21st
century (Holland et al., 2006). Rising summertime air temperatures suggest that glaciers may
disappear altogether in the Alps by 2100 (Zemp et al., 2006) and contribute substantially to
rising sea levels (Meier et al., 2007). Enhanced melting of the Greenland ice sheet and
potentially the Antarctic ice sheet will further advance sea level rise (Alley et al., 2005). Thus
global warming is anticipated to contribute to a shrinking cryosphere in the coming decades.
4
76
Repercussions of change
77
78
79
80
81
82
83
84
Changes in the cryosphere have profound environmental, biological and societal
repercussions (Barnett et al., 2005). As an example, mass wasting of glaciers has significant
implications on downstream freshwater resources and hydrological processes. Glacier
recession in western Canada has led to declines and phase shifts in late summer streamflow
(Stahl and Moore, 2006; Déry et al., 2009). This has important ramifications for populated
downstream areas such as the arid Canadian Prairies that are now subject to an impending
water crisis (Schindler and Donahue, 2006). Furthermore, glacier and ice sheet melt
contributes to rising sea levels and potential changes in ocean currents (Alley et al., 2005).
85
86
87
88
89
90
91
Modifications in snowpack characteristics also affect ecological processes such as the
duration of the growing season (Vaganov et al., 1999), and on plant productivity, density,
and distribution. Changes in snowpack accumulation influence prey-predator relationships
(Stenseth et al., 2004) and the feeding habits of mountain caribou and other ungulates
(Kinley et al., 2007). The potential collapse in the populations of polar bears in the Arctic
(Durner et al., 2009), emperor penguins in Antarctica (Jenouvier et al., 2009), and other
species forms another potential consequence of a shrinking cryosphere.
92
93
94
95
96
97
98
99
Furthermore, cryospheric changes influence socioeconomic and recreational activities. The
potential opening of the Northwest Passage in the Canadian Archipelago may lead to
increased shipping activity in the high Arctic. Warmer winters have led to shorter periods
with river ice covers in northern Canada, impeding commercial transport on ice roads
(Hinzman et al., 2005). Tourism may suffer from the degradation of glaciers in many regions
including Waterton National Park in the Canadian Rocky Mountains (Scott et al., 2007).
Outdoor recreational activities such as skiing and ice skating may also be curtailed owing to
reduced or unreliable snow/ice packs (Elsasser and Bürki, 2002; Visser and Petersen, 2009).
100
Summary
101
102
103
104
105
106
107
108
Rising air temperatures are inducing dramatic changes in the state of the cryosphere. Global
warming has led to a general decline in the presence of snow, ice and glaciers over the past
decades. Future projections of climate suggest that changes in the cryosphere will intensify
and accelerate over the 21st century in response to continued global warming. The
disappearance of snow, ice and glaciers will reduce freshwater storage on the land surface,
leading to diminishing water resources in many areas. Given the increasing demands for
freshwater, changes in the cryosphere driven by global warming may pose serious challenges
to humans and ecosystems in the 21st century.
109
Stephen J. Déry
110
Bibliography
111
112
Alley, R. B., P. U. Clark, P. Huybrechts, and I. Joughin (2005), Ice sheet and sea-level
changes. Science, 310: 456-460.
5
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
Barnett, T. P., J. C. Adam, and D. P. Lettenmaier (2005), Potential impacts of a warming
climate on water availability in snow-dominated regions. Nature, 438: 303-309.
Brown, R. D. (2000), Northern Hemisphere snow cover variability and change, 1915-97.
Journal of Climate, 13: 2339-2355.
Brown, R. D., and R. O. Braaten (1998), Spatial and temporal variability of Canadian
monthly snow depths. Atmosphere-Ocean, 36: 37-54.
Cavalieri, D. J., P. Gloersen, C. L. Parkinson, J. C. Comiso, and H. J. Zwally (1997),
Observed hemispheric asymmetry in global sea ice changes. Science, 278: 1104-1106.
Curtis, J., G. Wendler, R. Stone, and E. Dutton (1998), Precipitation decrease in the western
Arctic, with special emphasis on Barrow and Barter Island, Alaska. International Journal
of Climatology, 18: 1687-1707.
Déry, S. J., and R. D. Brown (2007), Recent Northern Hemisphere snow cover extent trends
and implications for the snow-albedo feedback. Geophysical Research Letters, 34:
L22504, doi:10.1029/2007GL031474.
Déry, S. J., and E. F. Wood (2006), Analysis of snow in the 20th and 21st century
Geophysical Fluid Dynamics Laboratory coupled climate model simulations. Journal of
Geophysical Research, 111: D19113, doi:10.1029/2005JD006920.
Déry, S. J., Stahl, K., Moore, R. D., Whitfield, P. H., Menounos, B. and Burford, J. E., 2009:
Detection of runoff timing changes in pluvial, nival and glacial rivers of western Canada.
Water Resources Research, 45: doi:10.1029/2008WR006975.
Durner, G. M., D. C. Douglas, R. M. Nielson, S. C. Amstrup, T. L. McDonald, I. Stirling, M.
Mauritzen, E. W. Born, O. Wiig, E. DeWeaver, M. C. Serreze, S. E. Belikov, M. M.
Holland, J. Maslanik, J. Aars, D. A. Bailey, and A. E. Derocher (2009), Predicting 21st
century polar bear habitat distribution from global climate models. Ecological
Monographs, 79: 25-58.
Dyurgerov, M. B., and M. F. Meier (2000), Twentieth century climate change: Evidence
from small glaciers. Proceedings of the National Academy of Sciences of the United
States of America, 97: 1406-1411.
Elsasser, H. and R. Bürki (2002), Climate change as a threat to tourism in the Alps. Climate
Research, 20: 253-257.
Frei, A., and G. Gong (2005), Decadal to century scale trends in North American snow extent
in coupled atmosphere-ocean general circulation models. Geophysical Research Letters,
32: L18502, doi: 10.1029/2005GL023394.
Hinzman, L. D., N. D. Bettez, W. R. Bolton, F. S. Chapin, M. B. Dyurgerov, C. L. Fastie, B.
Griffith, R. D. Hollister, A. Hope, H. P. Huntington, A. M. Jensen, G. J. Jia, T.
Jorgenson, D. L. Kane, D. R. Klein, G. Kofinas, A. H. Lynch, A. H. Lloyd, A. D.
McGuire, F. E. Nelson, W. C. Oechel, T. E. Osterkamp, C. H. Racine, V. E.
Romanovsky, R. S. Stone, D. A. Stow, M. Sturm, C. E. Tweedie, G. L. Vourlitis, M. D.
Walker, D. A. Walker, P. J. Webber, J. M. Welker, K. S. Winkler, and K. Yoshikawa
(2005), Evidence and implications of recent climate change in northern Alaska and other
Arctic regions. Climatic Change, 72: 251-298.
Holland, M. M., C. M. Bitz, and B. Tremblay (2006), Future abrupt reductions in the summer
Arctic sea ice. Geophysical Research Letters, 33: L23503, doi: 10.1029/2006GL028024.
Jenouvier, S, H. Caswell, C. Barbraud, M. Holland, J. Stroeve, and H. Weimerskirch (2009),
Demographic models and IPCC climate projections predict the decline of emperor
6
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
penguin population. Proceedings of the National Academy of Sciences of the United
States of America, 106: 1844-1847.
Kinley, T. A., T. Goward, B. N. McLellan, and R. Serrouya (2007), The influence of variable
snowpacks on habitat use by mountain caribou. Rangifer, 17: 1-10.
Magnuson, J. J., D. M. Robertson, B. J. Benson, R. H. Wynne, D. M. Livingstone, T. Arai, R.
A. Assel, R. G. Barry, V. Card, E. Kuusisto, N. G. Granin, T. D. Prowse, K. M. Stewart,
and V. S. Vuglinski (2000), Historical trends in lake and river ice cover in the Northern
Hemisphere. Science, 289: 1743-1746, doi: 10.1126/science.289.5485.
Maslanik, J. A., C. Fowler, J. Stroeve, S. Drobot, J. Zwally, D. Yi, and W. Emery (2007), A
younger, thinner Arctic ice cover: Increased potential for rapid, extensive sea-ice loss.
Geophysical Research Letters, 34: L24501, doi: 10.1029/2007GL032043.
Meier, M. F., M. B. Dyugerov, U. K. Rick, S. O’Neel, W. T. Pfeffer, R. S. Anderson, S. P.
Anderson, A. F. Glazovsky (2007), Glaciers dominate eustatic sea-level rise in the 21st
century. Science, 317: 1064-1067.
Mote, P. W., A. F. Hamlet, M. P. Clark, and D. P. Lettenmaier (2005), Declining mountain
snowpack in western North America. Bulletin of the American Meteorological Society,
86: 39-49.
Oerlemans, J. (2005), Extracting a climate signal from 169 glacier records. Science, 308:
675-677.
Räisänen, J. (2008), Warmer climate: Less or more snow? Climate Dynamics, 30: 307-319.
Rignot, E., and P. Kanagaratnam (2006), Changes in the velocity structure of the Greenland
Ice Sheet. Science, 311: 986-990, doi: 10.1126/science.1121381.
Rignot, E., G. Casassa, P. Gogineni, W. Krabill, A. Rivera, and R. Thomas (2004),
Accelerated ice discharge from the Antarctic Peninsula following the collapse of Larsen
B ice shelf. Geophysical Research Letters, 31: L18401, doi: 10.1029/2004GL020697.
Rothrock, D. A., Y. Yu, and G. A. Maykut (1999), Thinning of the Arctic sea-ice cover.
Geophysical Research Letters, 26: 3469-3472.
Rott, H., P. Skvarca, and T. Nagler (1996), Rapid collapse of Northern Larsen Ice Shelf.
Science, 271: 788-792.
Schindler, D. W., and W. F. Donahue (2006), An impending water crisis in Canada’s western
prairie provinces. Proceedings of the National Academy of Sciences of the United States
of America, 103: 7210-7216.
Scott, D., B. Jones, and J. Konopek (2007), Implications of climate and environmental
change for nature-based tourism in the Canadian Rocky Mountains: A case study of
Waterton Lakes National Park. Tourism Management, 28: 570-579.
Stahl, K., and R. D. Moore (2006), Influence of watershed glacier coverage on summer
streamflow in British Columbia, Canada. Water Resources Research, 42: W06201, doi:
10.1029/2006WR005022.
Stenseth, N. C., A. Shabbar, K.-S. Chan, S. Boutin, E. K. Rueness, D. Ehrich, J. W. Hurrell,
O. C. Lingjærde, and K. S. Jakobsen (2004), Snow conditions may create an invisible
barrier for lynx. Proceedings of the National Academy of Sciences of the United States of
America, 101: 10632-10634.
Stieglitz, M., S. J. Déry, V. E. Romanovsky, and T. E. Osterkamp (2003), The role of snow
cover in the warming of arctic permafrost. Geophysical Research Letters, 30: 1721, doi:
10.1029/2003GL017337.
7
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
Stone, R. S., E. G. Dutton, J. M. Harris, and D. Longenecker (2002), Earlier spring snowmelt
in northern Alaska as an indicator of climate change. Journal of Geophysical Research,
107: 4089, doi: 10.1029/2001JD000677.
Stroeve, J., M. M. Holland, W. Meier, T. Scambos, and M. Serreze (2007), Arctic sea ice
decline: Faster than forecast. Geophysical Research Letters, 34: L09501, doi:
10.1029/2007GL029703.
Tedesco, M., X. Fettweis, M. van den Broeke, R. van de Wal, and P. Smeets (2008), Extreme
snowmelt in northern Greenland during summer 2008, Eos Transactions AGU, 89(41),
doi:10.1029/2008EO410004.
Vaganov, E. A., M. K. Hughes, A. V. Kidyanov, F. H. Schweingruber, and P. P. Silkin
(1999), Influence of snowfall and melt timing on tree growth in subarctic Eurasia.
Nature, 400: 149-151.
Visser, H. and A. C. Petersen (2009), The likelihood of holding outdoor skating marathons in
the Netherlands as a policy-relevant indicator of climate change. Climatic Change, 93:
39-54.
Ye, H. C., and M. Ellison (2003), Changes in transitional snowfall season length in northern
Eurasia. Geophysical Research Letters, 30: 1252, doi: 10.1029/2003GL016873.
Ye, H., H. R. Cho, and P. E. Gustafson (1998), The changes in Russian winter snow
accumulation during 1936-83 and its spatial patterns. Journal of Climate, 11: 856-863.
Zemp, M., W. Haeberli, M. Hoelzle, and F. Paul (2006), Alpine glaciers to disappear within
decades? Geophysical Research Letters, 33: L13504, doi:10.1029/2006GL026319.
224
Cross-references
225
226
227
228
229
230
231
232
233
234
235
Cryosphere
Deglaciation
Depletion of snow cover
Glaciers as indicators of climate change
Impact of snow cover and glaciers on runoff
Lake ice
Retreat/advance of glaciers
Sea ice
Streamflow trends in the mountainous region
Thinning of Arctic sea-ice cover
Thinning of glacier (downwasting)