snowline

The snowline is the boundary in a mountainous region where snow-covered ground ends and snow-free ground begins for a given period, typically defined by the extent of snow persisting through the warm season. It varies with latitude, climate, and season, and it is higher in warmer, sunnier areas and lower in cooler, wetter ones. In temperate mountains, the snowline shifts seasonally, being higher in summer and lower in winter.

Two related concepts are often used: the seasonal snow line, which denotes the altitude where snow remains through the summer, and the permanent snow line (also called the equilibrium line altitude on glaciers), which marks the altitude above which snow persists year-round.

Multiple factors influence the snowline, including temperature, precipitation patterns, solar radiation, wind, and terrain aspects such as slope and orientation. Latitude also plays a major role. Snowlines are measured and monitored using field observations, aerial surveys, and remote sensing, with maps and models tracking their changes over time.

The snowline has practical and scientific importance. It affects regional hydrology by regulating meltwater and river discharge, influences glacier dynamics and watershed ecology, and serves as a climate indicator: an upward shift in the snowline over time is commonly associated with warming trends. Changes in snowline altitude can impact water resources, habitat, and alpine technologies such as hydroelectric power.