WhiteCAP_Plan_01SEPT..

Northern Climate ExChange WhiteCAP Draft Plan
4.0 Climate and Whitehorse
The city of Whitehorse is located in the Upper Yukon-Stikine Basin climate region of
Yukon (Whal et al, 1987). This climate region is influenced by the St Elias/Coast
Mountain Ranges, which create a rain shadow. This rain shadow influences the amount
of precipitation that falls in the region, typically 200 to 325mm per annum (Yukon
Ecoregions Working Group, 2004). Mean annual temperature for the region is -1°C to -
2°C (Yukon Ecoregions Working Group, 2004). The northwest-southeast orientation of
the valley in which Whitehorse has been developed ensures the city is the most
consistently windy location in the region (Whal et al, 1987).
This section summarizes the climate of Whitehorse. Past trends in precipitation and
temperature are provided. As well, climate projections through to the 2050’s are
provided. Trends and projections are compared to climate normal from 1961-1990.
Projected climate changes to the Whitehorse area were generated by the Scenarios
Network for Alaska Planning (SNAP). SNAP is located at the University of Alaska-
Fairbanks. The trend analysis was completed by NCE over the winter of 2010.
4.1 Past Climate Trends in the Whitehorse Area
Climate has been changing in Whitehorse. It is clear from meteorological data going
back to the 1940’s that temperature has been warming, especially in winters. Winter also
has the greatest variability in temperature. Break up has been arriving earlier, freeze up
later and growing degree days have been increasing. Past climate trends give us a
context from which to evaluate local climate and also a sense whether or not the climate
has been changing. Trends can be compared against projections of future climate, such
as those provided in the next section. Where the trend agrees with projections, our
confidence in knowing the future climate increases. Where the trends disagree with
projections, our confidence decreases.
Whitehorse is semi-arid. While there has been a small increase in precipitation over
recent decades, there is already a great deal of variability in precipitation and therefore,
the trend is difficult to discern. Further, some data from recent decades has been lost.
Non-parametric trend analysis (thus avoiding biases associated with missing data) show
that winter precipitation is trending down. The trends for temperature and precipitation
are provided in Table 4.1.
Flow data is available for the Yukon River at Whitehorse. Warming trends and the
melting of the glaciers which feed the Upper Yukon Basin have increased lake levels in
the system above Whitehorse but have not resulted in appreciable increase in overall
annual flow of the Yukon River through Whitehorse. Seasonal variation in flow has
changed, but this is most likely to be as a result of hydrological control systems operated
by Yukon Energy and not a change in the climate system. Flooding is not typically
associated with peak flow in summer, but is instead related to both freeze up (and ice
damming) and spring melt (especially in heavy snow years with rapid melt onset).
Standard meteorological data show a decreasing trend for wind at Whitehorse. However,
more detailed research using weather balloons show a clear increase in wind. This
contradiction is likely explained by changes to the horizon as trees have grown up or
been replaced by buildings. Both trees and buildings will break the wind and affect
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