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In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed . (1998). 9780340584316, Arnold. ISBN 9780340584316 (1996). 9780471963455, John Wiley & Sons. ISBN 9780471963455 (2025). 9783642034145, Springer. ISBN 9783642034145
Ice caps significantly affect the geomorphology of the area they occupy. Plastic moulding, gouging and other glacial features become present upon the glacier's retreat. Many lakes, such as the Great Lakes in North America, as well as numerous valleys have been formed by glacial action over hundreds of thousands of years.
The Antarctic and Greenland contain 99% of the ice volume on earth, about of total ice mass.
The shape of an ice cap is determined by the landscape it lies on, as melting patterns can vary with terrain. For example, the lower portions of an ice cap are forced to flow outwards under the weight of the entire ice cap and will follow the downward slopes of the land.
Ice caps accumulate snow on their upper surfaces, and ablate snow on their lower surfaces. An ice cap in equilibrium accumulates and ablates snow at the same rate. The AAR is the ratio between the accumulation area and the total area of the ice cap, which is used to indicate the health of the glacier. Depending on their shape and mass, healthy glaciers in equilibrium typically have an AAR of approximately 0.4 to 0.8. The AAR is impacted by environmental conditions such as temperature and precipitation.
Data from 86 mountain glaciers and ice caps shows that over the long term, the AAR of glaciers has been about 0.57. In contrast, data from the most recent years of 1997–2006 yields an AAR of only 0.44. In other words, glaciers and ice caps are accumulating less snow and are out of equilibrium, causing melting and contributing to sea level rises.
Assuming the climate continues to be in the same state as it was in 2006, it is estimated that ice caps will contribute a 95 ± 29 mm rise in global sea levels until they reach equilibrium. However, environmental conditions have worsened and are predicted to continue to worsen in the future. Given that the rate of melting will accelerate, and by using mathematical models to predict future climate patterns, the actual contribution of ice caps to rising sea levels is expected to be more than double from initial estimates.
Plateau glaciers are glaciers that overlie a generally flat highland area. Usually, the ice overflows as hanging glaciers in the lower parts of the edges. An example is Biscayarfonna in Svalbard.
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