According to a new climate change study led by the National Center for Atmospheric Research, it will become more and more difficult to predict water resources in snow-dominated regions by the century's end.
Streamflow will become more variable and unpredictable even in regions that receive the same amount of precipitation. The amount and timing of water resources will become increasingly reliant on periodic episodes of rain as the amount and timing of water dwindles.
The lead author said that water managers will be at the mercy of individual precipitation events instead of having four to six months lead time. Climate change could cause water management systems in snow-dominated areas to be unreliable.
Observations show that the snowpack is falling in many areas.
The study warns that the changes in streamflow are likely to have cascading impacts on the ecosystems that rely on reliable water from snow. Although the changes won't be uniform across regions, more snow-free days and longer growing seasons will put stress on water resources and heighten fire risk.
The study assumes that emissions continue at a high rate. If society succeeds in reducing greenhouse gas emissions, the most severe impacts on the environment will likely be avoided.
The scientists drew on an advanced set of computer simulations to fill in details about the future of water resources, showing the extent to which changes in temperature and precipitation will alter snow accumulate and run off in the Northern Hemisphere. The new study looks at the increasing variability of water resources and not the impacts of climate change.
The study is going to be published in the National Academy of Sciences.
There is a race with predictable outcomes.
The melting of snow in the winter and the precipitation in the spring and summer regulates the flow of water. Scientists have warned for years that the snowpack will become thinner and melt earlier as more precipitation falls as rain instead of snow and as melting occurs at times during the winter.
The Community Earth System Model, version 2, was used by the authors to determine how reduced snowpack will affect water resources. They compared a past period with a future period using a database of simulations. The simulations were done on a computer in South Korea.
The results show how much of the world will see shifts in the timing and extent of water flows by the year 2200. Assuming high greenhouse gas emissions, there will be an average of 45 more snow-free days a year. Changes in sea ice will lead to the largest increases in the midlatitudes.
The largest loss in predictability will be experienced by regions that rely on the most predictable relationships between the snow and the water. The regions include the Rockies, Canadianarctic, Eastern North America, and Eastern Europe. The authors warn that this will make it more difficult to manage freshwater resources.
"We are in a race with predictability when it comes to streamflow because we're trying to improve our forecasts through better data, models, and physical understanding, but these efforts are being canceled by the rapid disappearance of our best predictor: snow." We need to study these topics because we are trying to win it.
The simulations show that the regions of East Asia, the Himalayas, and North America will keep their soil moist because of increased precipitation.
The co-author of the study said that snow-related metrics are critical for informed management of precious water resources. As utilities and civil works agencies plan new infrastructure to adapt to a changing climate, we need to address basic research questions about the changing characteristics of winter snow and resulting streamflow.
More information: Pervasive alterations to snow-dominated ecosystem functions under climate change, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2202393119 Journal information: Proceedings of the National Academy of Sciences
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