Chapter 3 - Climate change and melting glaciers

Abstract

Glacier ice, including ice sheets and ice caps, covers about 10% of the Earth's surface and stores 69% of freshwater. Over the last millennium, glaciers reached their maximum extent during the Little Ice Age but began to retreat at the end of the 19th century. Glacier wastage has been accelerating worldwide since the second half of the 20th century. Currently, glaciers across most of the polar and mountain regions have negative mass balance dominated by surface melt. This global trend is attributed to the continuing climatic warming. Glaciers in the Karakoram-Kunlun-Pamir region are a notable exception. Recent advancements in satellite data acquisition enabled more reliable assessments of mass balance of ice sheets. Increasing loss of ice from the Greenland and West Antarctic ice sheets and their peripheral glaciers has been observed since the 1990s. The combined glacier and ice sheet contribution is now the dominant source of global mean sea level rise. The Greenland ice sheet makes the largest contribution followed by a combined input from glaciers. Both significantly exceed that of Antarctica. Alaska, the Canadian Arctic, and the Southern Andes account for the largest contribution from glaciers. Glacier wastage is expected to continue in the future, and in many mountain regions glaciers may disappear or retreat to high elevations. Large uncertainty surrounds future evolution of ice sheets but there is a possibility that the Greenland ice sheet may decline to the point of no recovery.