Greenland ice sheet
The Greenland ice sheet is an ice sheet about 1.67 km (1.0 mi) thick on average, and almost 3.5 km (2.2 mi) at its thickest point. It is almost 2,900 kilometres (1,800 mi) long in a north–south direction, with the greatest width of 1,100 kilometres (680 mi) at a latitude of 77°N, near its northern edge. It covers 1,710,000 square kilometres (660,000 sq mi), around 80% of the surface of Greenland, and is the second largest body of ice in the world, after the East Antarctic ice sheet. The acronyms GIS or GrIS are also frequently used in the scientific literature.
| Greenland ice sheet | |
|---|---|
| Grønlands indlandsis Sermersuaq | |
| Type | Ice sheet |
| Coordinates | 76°42′N 41°12′W |
| Area | 1,710,000 km2 (660,000 sq mi) |
| Length | 2,400 km (1,500 mi) |
| Width | 1,100 km (680 mi) |
| Thickness | 1.67 km (1.0 mi) (average), ~3.5 km (2.2 mi) (maximum) |
While Greenland has had major glaciers and ice caps for at least 18 million years, a single ice sheet first covered most of the island some 2.6 million years ago. Since then, it has both grown, sometimes significantly larger than now, and shrunk to less than 10% of its volume on at least one occasion. Its oldest known ice is about 1 million years old. Due to greenhouse gas emissions by humans, the ice sheet is now the warmest it has been in at least the past 1000 years, and is losing ice at the fastest rate in at least the past 12,000 years.
Every summer parts of the surface melt, and ice cliffs calve into the sea. Normally the ice sheet would be completely replenished by the vast winter snowfall. But global warming is melting it two to five times faster than before 1850, and snowfall has not kept up since 1996. If the less stringent Paris Agreement goal of staying below 2 °C (3.6 °F) is achieved, then the melting of Greenland ice alone would add around 6 cm (2+1⁄2 in) to global sea level rise by the end of the century. If there are no efforts to reduce emissions, it would add around 13 cm (5 in) (and up 33 cm (13 in)) : 1302 For comparison, it has so far contributed 1.4 cm (1⁄2 in) since 1972, while the sea level rise from all sources was 15–25 cm (6–10 in)) between 1901 and 2018.: 5
If all 2,900,000 cubic kilometres (696,000 cu mi) of the ice sheet's volume were to melt, it would increase the global sea levels by ~5.1 m (17 ft) all on its own. Global warming between 1.7 °C (3.1 °F) and 2.3 °C (4.1 °F) would likely make this melting inevitable, unless it is then reduced to 1.5 °C (2.7 °F) above preindustrial levels or lower (i.e. through large-scale carbon dioxide removal) However, 1.5 °C (2.7 °F) still causes ice loss equivalent to 1.4 m (4+1⁄2 ft) of sea level rise, and more ice will be lost if the temperatures first exceed that level before coming down. If the temperatures do not decline, the ice sheet will disappear in 1,000 years with very high warming and in around 10,000 years otherwise.