A new study by researchers at the National Center for Atmospheric Research (NCAR) shows that as the world warms, mountain snowpack will not only melt earlier, it will also melt more slowly., reports Phys.org.
While the findings appear to be counterintuitive, they do have widespread implications for water supplies, ecosystem health, and flood risk, according to the study, funded by the National Science Foundation, NCAR’s sponsor and published in the journal Nature Climate Change.
“When snowmelt shifts earlier in the year, the snow is no longer melting under the high sun angles of late spring and early summer,” said NCAR postdoctoral researcher Keith Musselman, lead author of the paper. “The Sun just isn’t providing enough energy at that time of year to drive high snowmelt rates.”
Findings by researchers go a long way in explaining recent studies that found average streamflow in watersheds with snow-covered mountains may decline as the climate warms, even while the total amount of precipitation remains the same. The reason for this is that the snowmelt rate directly affects streamflow, according to Science News Online.
When the snowpack seems to linger, melting more slowly, more water is absorbed into the soil, giving plants a bigger opportunity to take up the moisture. But water taken up by plants is water that doesn’t reach the streams, potentially reducing streamflow.
Musselman became interested in the snowmelt rate while doing research in the Sierra Nevada Mountains. He noticed that at lower elevations, the shallower snowpack melted earlier but more slowly than the snowpack at higher elevations. Snowpack at high elevations tends to stick around until early summer when the sun is high and the days have grown longer. When the snowpack melt begins at this elevation, it usually is rapid.
This got Musselman to wondering if snowpack melts would change in the future with a warmer world that is expected to change higher elevation snowpack into what we see in lower-elevation snowpack today. To confirm his observations, he and his colleagues examined a decade’s worth of snowpack data from 979 stations in the U.S. and Canada, then they simulated snowpack for the same period using the NCAR-based Weather Research and Forecasting (WRF) model.
After confirming the output from WRF was in line with the observations, they used computer-generated simulations to investigate snowpack changes in North America at the end of the century if global warming continues unabated.
“We found a decrease in the total volume of meltwater – which makes sense given that we expect there to be less snow overall in the future,” Musselman said. “But even with this decrease, we found an increase in the amount of water produced at low melt rates and, on the flip side, a decrease in the amount of water produced at high melt rates.”
While the study did not investigate the range of implications that could arise out of the findings, Musselman says the impacts could be far-reaching. “We hope this study motivates scientists from many other disciplines to dig into our research so we can better understand the vast implications of this projected shift in hydrologic patterns,” Musselman said.
