A mechanism for regional variations in snowpack melt under rising temperature

As the planet warms, mountain snowpack is expected to melt progressively earlier each spring. However, analysis of measurements in the western United States shows that the change in the date when snowpack disappears is not uniform: for 1 degrees C of warming, snowpack disappears 30 days earlier in some regions, whereas there is almost no change in others. Here we present an idealized physical model that simulates the timing of snowpack melt under changing temperature and use it to show that this observed disparity in the sensitivity of snowpack disappearance to warming results from a mechanism related to the sinusoidal shape of the annual cycle of temperature. Applying this model globally, we show that under uniform warming the timing of snowpack disappearance will change most rapidly in coastal regions, the Arctic, the western United States, Central Europe and South America, with much smaller changes in the northern interiors of North America and Eurasia. Warming causes mountain snowpack to melt earlier during local spring. An idealized model suggests that melt date sensitivity to warming depends largely on mean temperature and its seasonal cycle; the largest sensitivities are seen in coastal regions, the Arctic, western United States, Central Europe and South America.

Automated summary

As the planet warms, mountain snowpack is expected to melt earlier in spring, with sensitivity to warming varying across regions. A physical model suggests that the timing of snowpack disappearance is largely influenced by mean temperature and seasonality, with the most significant changes seen in coastal regions, the Arctic, western United States, Central Europe, and South America.