Degrees of Change – Ice, Snow and Sea
2.0 The NRTEE’s Degrees of Change diagram: Illustrating the Impacts of Climate Change in Canada
Ice, Snow and Sea
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This category includes major reservoirs of water, each with different properties and functions for natural processes shaping life on Earth as we know it. On a global level, expanses of snow cover, land ice (including mountain glaciers), and sea ice provide a reflective surface that helps regulate the amount of energy from the sun that reaches the Earth’s surface. Oceans perform regulating functions as well, acting as vast reservoirs of heat from the atmosphere, redistributing excess heat toward the poles, and absorbing extra carbon from the atmosphere. Warming of the Earth’s surface since pre-industrial times has raised global sea levels, from a combination of the expansion of water in oceans and melting ice caps, mountain glaciers, and blocks of ice from land-based ice sheets (e.g., Antarctica and Greenland). Roughly a third of atmospheric carbon resulting from human activity has ended up in the global ocean. Ice in permafrost terrain locks in methane (a powerful greenhouse gas), serving as a climate regulating function. Thawing of permafrost also releases water and other compounds, influencing natural processes such as river hydrology.
For Canada, the significance of this category is two-fold. First, vast expanses of snow cover, land ice, sea ice, and permafrost within Canada’s territory, and our access to three oceans means that it’s important for us to understand how changes to our landscape and seascape contribute to global climate change. According to some estimates based on glacier inventories, ice covers just over 200,000 km² of Canada’s land mass.[8] Permafrost underlies half of Canada’s land surface.[9] Second, ice, snow, and our long coastline are also part of our national identity, influencing activities of Canadian households, communities, and businesses. We cover these linkages in impact categories below. Examples include reliance on permafrost stability for the integrity of infrastructure in parts of Canada’s North, and on snow conditions for winter recreation in several Canadian regions.
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What we can expect
SIGNIFICANT REDUCTIONS IN ARCTIC SEA ICE.
The past 30 years saw the extent of summertime sea ice in the Arctic decline by about 10% per decade, compared to the 1979 to 2000 average, and in 2007 it was 30% below average (see Box 4).[10] Global climate models project a 50% reduction in the extent of summertime sea ice and in concentrations in the Canadian Arctic at global temperatures between 2 and 3°C above pre-industrial averages,[11] with reductions in sea ice happening at an accelerating rate at global temperatures above 2°C.[12] Other research suggests that a completely ice-free Canadian archipelago is unlikely by 2050[13], with models projecting an ice-free Arctic ocean in late summer by the end of the 21st century (3 to 5°C over pre-industrial levels).[14] However, the observed decreases in summertime sea-ice extent have taken place faster than climate models projected,[15] so the declining trend in Arctic sea ice toward ice-free summer conditions could occur sooner and to a greater extent than either anticipated or presented here.
This transformation of the Arctic has immediate implications for marine and land-based plants and animals, for northern peoples and their livelihoods, and for national security. In addition, disappearing Arctic sea ice means that the Arctic Ocean is absorbing more solar energy, further contributing to global climate warming.
INCREASING DEPTH OF SEASONAL THAW IN PERMAFROST TERRAIN.
Over the past 60 years, air temperatures in the Mackenzie Valley region of the Northwest Territories have increased more than any other climate region in Canada, with implications for ground temperatures and the integrity of permafrost. Indeed, in this same region, the depth to which the ground thaws in the summer could increase 15 to 40% over the next century, in response to global climate warming of 3 to 4°C.[16] Permafrost terrain overlain by a thick layer of organic material, such as soil and vegetation, will see smaller changes in thaw depth.
Almost all glaciers in Canada are already retreating. Glaciers in British Columbia and Alberta have shrunk in area by an average of 0.55% per year between 1985 and 2005.
[17] This recent shrinkage is not just due to global climate warming but also to natural variability on the scale of decades in the way moisture is distributed across the region.[18] Increases in global temperatures of about 2 to 4°C could reduce the volume of western mountain glaciers by over 50%.[19] Smaller glaciers may well disappear over the next 100 years,[20] with summer melting outstripping any modest gains in snow and ice accumulated in winter in some locations.[21]
Over much of Canada, warmer average temperatures since the 1980s have prompted snow to melt earlier in the spring and reduced the depth of snow cover.[22] In the Pacific Northwest, a greater proportion of winter precipitation is falling as rain than has been the case in the past, reducing the mountain snowpack.[23] At global temperatures on average about 3°C higher than pre-industrial levels, climate models project an increase in snow accumulation in Canada’s high Arctic in response to warmer air and more open water.[24]
Global sea levels have risen an estimated 0.17 m since 1870.[25] Recent estimates suggest that global sea-level rise could reach between 0.50 m and 1 m by the end of the century,[26] corresponding to global temperatures between about 2.5°C and 5°C above pre-industrial levels. Other research shows the possibility of global sea-level rise exceeding 1.5 m also by 2100.[27] The effects of this sea-level rise will vary by location. Actual changes in sea levels depend on local physical properties: whether land is subsiding or facing uplift. Coastlines particularly sensitive to the effects of sea-level rise include those with low relief and low resistance to erosion, those exposed to high-energy waves, and those with large ranges between high and low tides. Projected rates of sea-level rise will have direct impacts on communities and ecosystems in low-lying coasts throughout Canada, particularly in the Atlantic coast, the Beaufort Sea coast, and part of the lower mainland of British Columbia. Coastal ecosystems, such as wetlands and marshes, are already facing “coastal squeeze,” with human development creating a barrier to natural migration inland.
What we can do about it
The effects of warmer global temperatures are most observable on our physical environment, including ice, snow, and sea levels. Broadly speaking, we can do little to reduce the effects of a changing climate on these systems in Canada, other than limit global climate change itself. A few examples do exist of technologies developed or practices adopted to resist or adapt to changes in ice systems driven by warmer temperatures. In Canada’s North, governments and industry have taken measures to inhibit permafrost warming and minimize ground settlement underlying major infrastructure projects, including the installation of “thermosyphons.” Some northern residents reliant on frozen waterways for travelling, fishing and hunting activities have started using maps containing satellite images of up-to-date ice conditions to guide their decisions.[28] The effectiveness of technologies such as these and the feasibility of their continued application will depend on the extent of change in the physical environment and the rate at which change takes place.
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Footnotes
8 Natural Resources Canada, 2004, “Glaciers and Icefields,” The Atlas of Canada, http://www.atlas.nrcan.gc.ca/site/english/maps/freshwater/distribution/glaciers/1 as cited in Statistics Canada (2008).
9 Atlas of Canada – Permafrost map (http://atlas.nrcan.gc.ca/site/english/maps/environment/land/permafrost
10 Lawrence et al. (2008); see also trend data from the National Snow and Ice Data Center at http://nsidc.org/arcticseaicenews/
11 Reading Figure 10.13 in Meehl et al. (2007), using an A2 or A1B scenario, we see a projected 50% reduction in summertime (July-August-September) ice extent relative to the period 1980 to 2000 around 2070 (central estimate), which corresponds to a global average temperature increase (from pre-industrial) of about 2.7°C using a central estimate from Figure 10.5 (Meehl et al. [2007]) (Dr. Greg Flato, personal communication, March 24, 2010). Sou and Flato (2009) find ice concentrations in the Canadian Arctic Archipelago to decrease by 45% by 2050 under a SRES A2 scenario, which corresponds to a best estimate of about 2.2°C (likely range 1.8-2.7), according to IPCC AR4 WGII Technical Summary Figure TS4. The NRTEE chose the 50% reduction in sea-ice extent to highlight a threshold that might resonate with readers.
12 National Academy of Sciences (2010), page 27.
13 Sou and Flato (2009).
14 Estimates for ice-free Arctic summers range from 2037 to 2100 (Wang and Overland [2009], Boe et al.[ 2009], Arzel et al.[ 2006], as cited in National Academy of Sciences[ 2010]).
15 Stroeve et al. (2007).
16 Woo et al.( 2007). This study used scenarios A2 and B2; ~3.5°CC lies between the best estimates of those two scenarios in 2100 (2090s), within a range of 3.1-4.2°C.
17 Bolch et al. (2010). Bolch et al’s (2010) inventory of western Canadian glaciers suggests that glaciers in British Columbia and Alberta respectively lost −10.8±3.8% and −25.4%±4.1% of their area over the period 1985–2005. The region-wide annual shrinkage rate of −0.55% per year is comparable to rates reported for other mountain ranges in the late twentieth century. We position this impact statement at 0.6°C due to the difference in the global average temperature between the degrees of change diagram’s pre-industrial baseline and 1985–2005, the period of Bolch et al’s study.
18 M. Demuth (Natural Resources Canada), personal communication, April 1, 2010.
19 Schneeberger et al.( 2003) project an average 60% loss in volume of a sub-set of glaciers in the northern hemisphere by 2050 under a global temperature rise consistent with a transient 2 x CO2 equivalent corresponding to a IS92a emissions scenario. This subset includes glaciers in Alaska and northwest US. The global temperature rise over pre-industrial levels corresponding to 550 parts per million for the 2050s is a best estimate of about 2.1°C (range of 1.6-2.3°C), reading from Figure TS4, Technical Summary, IPCC (2007) WGII.
20 Walker 7 Sydneysmith( 2008); Matulla et al, (2009). Continued shrinkage of smaller glaciers is likely to continue beyond 2050 and may well result in total loss of some glaciers: “Most of BC’s glaciers are losing mass and many will disappear in the next 100 years” (Walker and Sydneysmith [2008], page 341 – Box 1).
21 Focusing on the Peyto Glacier in Alberta, Matulla et al. (2009) conclude that moderate increases in winter snow and ice accumulations will not compensate for increased summer melt, leading to net wastage and potential disappearance of the glacier by 2100 (all scenarios range for 2090s is 2.5-4.8°C over pre-industrial levels, reading off Figure TS4, Technical Summary, IPCC (2007) WGII).
22 Zhang et al. (2010). This is a technilca report that fed into the Canadian Biodiversity: Ecosystem Status and Trends 2010 report, a collaborative effort of the federal, provincial, and territorial governments of Canada. For further information, see http://www.biodivcanada.ca/default.asp?lang=En&n=E0DDE11F-1#X-201010191259305
23 Mote (2006).
24 Räisänen (2008); Brown and Mote (2009); Dr. Ross Brown, personal communication, March 29, 2010. Räisänen (2008) used an A1B scenario for the 2080s, which is associated with best estimate of 3.3°C in the 2080s (likely range: 2.6-4.3°C).
25 Solomon et al.( 2007), TS18 – Bindoff et al. (2007) in Solomon et al.
26 National Academy of Sciences (2010), page 123 indicates an estimated range of global sea-level rise in 2100 of about 0.5 to 1m (using an A1B scenario). For that same scenario, Horton et al. (2008) project a global sea-level rise of 0.62 to 0.88m from 2001–2005 levels by 2100.
27 Vermeer & Rahmstorf (2009) project a sea-level rise of 0.97 to 1.56m above 1990 levels by 2100, based on global warming driven by an A1B scenario of global emissions. Pfeffer et al. (2008) conclude “that sea-level rise in the 21st century is very unlikely to exceed 2m.”
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