Icecap

An ice cap is a dome-shaped mass of glacier ice that covers less than 50,000 square kilometers (about 19,000 square miles) of land. If the ice cover exceeds this size, the feature is typically described as an ice sheet. Ice caps are formed where snowfall accumulates over many years and remains after summer ablation; the compressed snow gradually becomes ice and thickens, causing the ice to flow outward from the center.

Ice caps are driven by gravity and topography. Their movement is slow and laminar at the core but can develop crevasses, seracs, and moulins at the margins where the ice interacts with bedrock and meltwater. They are distinct from sea ice and from large ice sheets, though their dynamics can influence regional hydrology and local climate. Ice caps also help regulate regional albedo and act as freshwater reservoirs for nearby ecosystems and human use.

Geographically, ice caps occur in polar regions and on high mountains. Notable examples include the Icelandic Vatnajökull complex and various caps in the Canadian Arctic and the European Alps. The exact boundaries and definitions of what constitutes an ice cap can vary by source, with the 50,000 square kilometer threshold commonly used to distinguish ice caps from ice sheets.

Climate-change impacts are evident in many regions: rising temperatures can increase ablation, reduce thickness and extent, and alter meltwater timing. This affects downstream water resources, sea-level contributions from land-based ice, and regional landscapes. Ice caps remain important indicators of climatic trends and hydrological extremes.