Mountains in the western United States have lost between 10 and 20 percent of their annual snowpack since the 1980s partly due to human influences, researchers have found. They are predicting a further loss of up to 60 percent over the next three decades, with profound consequences for water supply and hydropower.
The team of scientists, including climate modellers from the Canadian Centre for Climate Modelling and Analysis (CCCma) at the University of Victoria, considered observations from the US Natural Resource Conservation Service Snow Telemetry (SnoTel) network of automated data collection sites located in remote mountain watersheds. The network is used to forecast water supplies. The researchers focused on stations producing data from higher than 1,500 metres and from the post-1981 period. Observations prior to this date were too sparse.
Snowpack is the snow that falls onto the ground and sticks around until spring. The data gathering is automatically performed by special instruments called ‘snow pillows’, which measure the weight of the snow and figure out how much water there would be if were to melt.
These snowpack observations were then checked against two sets of current climate simulations covering a broad region of the western US run in the past rather than the future. One set of simulations included the observed changes in the chemical composition of the atmosphere due to human activities, notably greenhouse gas emissions but also land-use changes and ozone. The other looked at just natural effects, such as volcanic eruptions and solar activity.
They found that the real-world observations were in keeping with their computer model results only if the observed changes in the chemical composition of the atmosphere due to human activities. Absent these anthropogenic changes, there is not likely to be such snowpack loss.
Based on the accuracy of these models and the current state of the snowpack, the researchers reckon that the region can expect up to a further annual maximum snowpack loss of 60 percent over the next 30 years, a relatively short period.
This could be a major problem, as the melting snow is a key source of the water in streams.
“The projected losses have serious implications for the hydropower, municipal and agricultural sectors in the region,” said lead researcher John Fyfe, whose findings were reported last week in Nature Communications. Forest vulnerability to fire could also be increased, and forest productivity, and carbon storage in forests could be diminished.
Natural decade-to-decade variability may offset some of this human-caused snowpack loss. But the researchers say that the greatest concern is that this natural variability also has the potential to substantially enhance this near-term decline as well.
Despite the warning over hydropower, the paper is about the US and the situation for that country faces potentially bigger impacts on this front than British Columbia.
Given the recent heavy snowfall experienced in many urban areas of British Columbia, many people might think that the 2016-17 winter offered some respite from the snowpack decline. However, despite the breaching of single-day snowfall records right across the province, snowpack was actually about 79 percent of normal, according to the BC River Forecast Centre.
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