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Glaciers 28
Like snowmelt, glaciers are also an important contributor to water resources. Yet, contrary
to snowmelt, their influence extends from seasons to decades. During the late summer,
when
rivers typically experience low flows and ecological requirements are high, glacier
runoff may be a large faction of the streamflow.
According to the IPCC, global glacier loss will continue throughout the 21st century because
increased melt rates will exceed supplements from increased snowfall. 29 More specifically,
based on the IPCC IS92a (or “business‐as‐usual”) scenario, glacier surface area globally is
expected to decrease by 38 % and 34 % by 2025 and 2050, respectively. 30 Given the data
limitations, the behavior of glaciers in the XGCA watersheds is hard to predict with
any certainty. Adding to the lack of data explained above, another key challenge is that due
to the presence of more than 10,000 glaciers in Western Canada, projected changes cannot
be made with fully dynamic glaciological models for all glaciers, although these models may
serve well for projecting changes at individual glaciers. What is clear, though, most of
BC’s glaciers are losing mass and many will disappear in the next century. 31 This will
undoubtedly
influence river discharges and temperature in a negative way in the
XGCA.
A strong example is provided in Figure 8, where projections for Bridge glacier highlight
substantial reductions of its mass area by up to 20 percent by the 2050s even without
further warming of the current climate. The figure also shows a subsequent marked
reduction (37%) in the mean August (summer) stream flow from approximately 2005 to
2145, even when based on a continuation of the present climate. When the present climate
was substituted with projected warmer temperatures in the applied models, the glacial
trends got even stronger. These projected changes will be the result of the projected
increases
in air temperature and prevalence of precipitation falling as rain rather than
snow. 32
It should be noted that the Bridge glacier is located in the southern BC, so it is not of direct
relevance to the water bodies of the XGCA. This projection is still alarming, though, as the
Bridge glacier covers the largest fraction of watershed area in BC. In addition, these results
suggest that for most of BC the phase of increased streamflow that generally follows climate
warming has passed and continued reduction in glacier area will lead to decreased
streamflow. In other words, the future will see less water in the water bodies.
28 This section is based solely on PCIC (2007revised 2009), unless other source
is stated.
29 IPCC Technical Summary for the Fourth Assessment Report
30 Bush, A., and Pollock, T. (2009); Personal Communication (Nov. 2009).
31 Walker, I.J. and Sydneysmith, R. (2008).
32 Stahl, K., Moore, R.D., Shea, J.M., Hutchinson, D. and Cannon, A., (2007 in press).
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