The Greenland ice sheet is a large body of ice that covers approximately 80% of the surface of Greenland. At 1.7 million square kilometres (3 times the size of the province of Alberta) it is the second largest ice body in the world. The Greenland ice sheet is however much smaller than the Antarctic ice sheet. The ice sheet is 2,400 kilometres long. These ice sheets are huge, and store a significant fraction of the world's fresh water.
In the past the Earth has often had less ice and at times had even more ice. For example, during the Pleistocene Ice Age, almost one third of the Earth’s land was covered by glacial ice. Today, about one tenth of the Earth’s land is covered by glacial ice. Right now, the Antarctic and Greenland ice sheets combined contain more than 99% of the freshwater ice on Earth.
The Greenland ice sheet interacts more intensely with the ocean than the Antarctic ice sheet. The annual snow accumulation rate is more than double that of Antarctica. Glacial melt happens across about half of the Greenland ice sheet, but melting is much more isolated on the far western part of Antarctica. Greenland's ice shelves break up much faster than those surrounding Antarctica.
Greenland ice sheets caused the land under them to sink; mainly the ice has depressed the central area of Greenland. If the continental glaciers were to abruptly disappear, the landscape in Greenland would change drastically. Greenland, the largest island in the world, would become an archipelago, which is a chain of small islands only connected by waterways.
Melting ice sheets contribute to rising sea levels. As ice sheets in Greenland melt, they raise the level of the ocean, putting coastal habitats at risk of being flooded. Melting ice sheets also reduce the ocean’s salinity. Tons of fresh water is added to the ocean every day by melting ice sheets. Large additions of freshwater change the ocean ecosystems. Organisms, such as coral, depend on saltwater for survival. Some corals can’t adjust to a higher freshwater concentration habitat. Thermohaline circulation, the ‘ocean conveyor belt’, would be radically altered by melting ice sheets. This circulation regulates nutrient rich water from polar regions throughout the world's oceans in a long, slow loop. Circulation is dependant on the relationship between water with different densities. Melting ice sheets would increase the amount of warm and freshwater in polar marine ecosystems. This would slow ‘deep water formation’, the development of cold, saline, nutrient rich water on which entire marine ecosystems depend. According to the United Nations, sea ice may decrease by 25% within the next century.
The video below is a lecture from Prof. David Archer, Department of Geophysical Sciences at the University of Chicago, talking about the Greenland Ice Sheet: