Overflatepåsmelting

Overflatepåsmelting, known in English as surface melt, refers to the process where snow or ice on the Earth's surface melts due to incoming solar radiation or warm air temperatures. This phenomenon is a crucial component of the cryosphere's response to climate change.

Surface melt occurs when the energy balance at the surface favors melting. This typically happens when air temperatures rise above freezing, but can also be influenced by increased absorption of solar radiation, often due to darker surfaces or impurities like dust and soot. The rate of melting is influenced by factors such as snow or ice albedo, surface temperature, humidity, wind speed, and the duration of warm conditions.

The meltwater produced can either drain into the snowpack or ice, refreeze, or flow away as surface runoff. In glaciers and ice sheets, surface melt is a primary contributor to mass loss, alongside iceberg calving. The meltwater can also form supraglacial lakes and rivers on the ice surface, which can then drain through crevasses and moulins to the glacier bed, potentially lubricating its movement and accelerating its flow.

On land, surface melt in snowpack is a major source of freshwater for rivers and ecosystems, particularly in mountainous regions. However, increased melt rates can lead to floods, landslides, and impacts on water availability downstream. Understanding and quantifying surface melt is therefore vital for climate modeling, hydrological forecasting, and assessing the vulnerability of polar regions and mountain environments.