Rising global temperatures will most likely result in mountain snowpack melting earlier in the year, but at a slower rate. While that may seem confusing at first, the mechanism is pretty easy to explain. Typically, most snowpack doesn’t start melting until the summer, when the sun in strongest in that region, and then it melts quickly.
But “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 study lead author Keith Musselman. “The Sun just isn’t providing enough energy at that time of year to drive high snowmelt rates.”
But rising temperatures will mean less snowfall generally, so there will be less snow—and that snow will be melting more slowly over a longer period. That means less danger of flashfloods in certain areas, but it can also have a number of negative impacts. For one, slower melting means less water ends up in streams because it gets soaked up by plants instead. This, in turn, means that the streams have less water, which can impact whole ecosystems, as well as urban water supplies that rely on seasonal snowmelt
“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.”
The impacts could reach far beyond the immediate area affected. Reductions in melt rates could mean fewer spring floods—which would be great for infrastructure, but not so good for the ecosystems that depend on those annual floods. The meltwater will likely be warmer, which could affect trout and other fish species.
These are some significant and problematic implications, though how exactly we can deal with such problems remains to be seen. Obviously, this is another piece of evidence in favor of working to combat global climate change.