The rise and fall in global ice cover is a function of climate change, when global surface temperatures are low, more ice accumulate on land, and sea level drops. And when temperature increases, melting of glaciers and ice sheet leads to rise in sea level.
Changes in glaciers and global warming over the last few decades can be best explained with the above images. The retreat of Alaska’s Colombia Glacier between 1980 and in 2005, and The Arapaho Glacier in the Rocky Mountains in Boulder County, Colorado between 1898 and 2003.
Section of Tidewater glacier, Columbia Glacier Alaska.
The Columbia is a tidewater glacier (terminates in water that contributes to sea-level rise mostly through iceberg calving). The Columbia Glacier flows down from the Chugach Mountains and into Prince William Sound about 40 miles west of Valdez, Alaska. Since the Columbia began retreating around 1980, the terminus—the ending edge—has retreated approximately 15 kilometers. Although the glacier is a big contributor to sea-level rise, its retreat is not directly tied to increased global temperatures and melting. Climate change may have given it a little initial nudge, but the processes that accelerated its disintegration were more physical than thermal.
The Arapaho is an alpine glacier that contributes to sea-level rise through melting. The retreat of mountain glaciers, on the other hand, is directly tied to increasing temperatures and melting. The Arapaho Glacier in the Rocky Mountains in Boulder County, Colorado, has shrunk dramatically since it was photographed in 1898. Measurements collected since 1960 suggest the glacier has thinned by more than 40 meters in 2003.
Compared to the contribution of tidewater glaciers, the volume of water added to the sea from melting alpine glaciers is very small.
Images courtesy of Tad Pfeffer, Institute of Arctic and Alpine Research, University of Colorado. Detailed image credits: 1) Columbia Glacier c. 1980 by Austin Post, U.S. Geological Survey, 2) Columbia Glacier 2005 by Tad Pfeffer, Institute of Arctic and Alpine Research, University of Colorado, 3) Arapaho Glacier 1898 by R.S. Brackett, published in Waldrop, R.S. (1964) Arapaho Glacier: A Sixty Year Record. University of Colorado Studies, Series in Geology, No 3, and 4) Arapaho Glacier 2003 by Tad Pfeffer.