3.4 Phase changes, including vapor diffusion
Radiation and conduction are processes that transfer thermal energy. Each induces changes in snowpack between solid ice, liquid water, and water vapor.
Melting is a phase change from solid ice to liquid water. As ice melts, it absorbs a great deal of energy from the surrounding environment, which significantly slows the warming of the snowpack. As a result, the temperature rise in a warming snowpack stalls at 0°C (the melting point) as ice changes to water. | ![]() |
Freezing is a phase change from liquid water to solid ice. As water freezes, it actually releases heat, which significantly slows the cooling of the snowpack. | ![]() |
Sublimation is a phase change from ice directly to water vapor. It occurs most commonly and quickly at the surface of a snowpack on dry, sunny days. Sublimation absorbs much more energy from the surrounding environment than melting, creating a shallow, stable layer just above the snowpack. This occurs despite the sunny conditions and inhibits the melting of the pack. | ![]() |