Meltwater

Meltwater is water released from the melting of snow and ice. It is a key component of the hydrological cycle, arising from snowpack, glaciers, ice sheets, or frozen lakes as temperatures rise or during precipitation events. Meltwater can reach streams and rivers as surface runoff, or move within or under ice through features such as moulins and crevasses, eventually contributing to proglacial rivers or lakes.

Sources and processes: Seasonal snowmelt from high-latitude or high-altitude regions generates large volumes of freshwater during spring and early summer. Glacier melt releases water continuously as temperatures rise. Rain-on-snow events can rapidly increase meltwater formation. Albedo changes when snow and ice melt reduce surface reflectivity, accelerating warming and melt.

Hydrological significance and effects: Meltwater sustains river flow during dry periods and supports aquatic ecosystems. It transports nutrients and sediments, shapes proglacial lakes, and can influence groundwater recharge. In some regions, large meltwater inputs affect ocean salinity and circulation patterns.

Climate change and variability: Warming temperatures generally increase melt rates and glacier retreat, altering the timing and volume of meltwater. Early-season surges can raise flood risk, while long-term changes affect water availability and ecosystem dynamics. Meltwater from land ice contributes to sea level rise as glaciers lose mass.

Measurement and research: Scientists monitor meltwater production using stream gauges, satellite imagery, and radar or lidar topography; modeling helps predict discharge and its ecological and climatic impacts.