Canada's Yuri Nazarkin carves Star Wars character C-3PO (R) and R2-D2 for the ice sculpture festival in Liege, Belgium, November 13, 2015. (Photo by Eric Vidal/Reuters)

A reindeer is seen as people visit ice sculptures illuminated by coloured lights at the Harbin Ice and Snow Festival to celebrate the new year in Harbin on January 4, 2017. (Photo by Nicolas Asfouri/AFP Photo)

Five hundred replicas of the Stormtrooper characters from "Star Wars" are placed on the steps at the Juyongguan section of the Great Wall of China during a promotional event for "Star Wars: The Force Awakens" film, on the outskirts of Beijing, China, October 20, 2015. (Photo by Jason Lee/Reuters)

A replica of the Wall-E character is remotely controlled with a mobile phone by Bolivian student Esteban Quispe, 17, in Patacamaya, south of La Paz, December 10, 2015. Quispe built the Wall-E robot using materials he obtained from a rubbish dump in the town located in the Andean highland region. He hopes to mechanize agriculture in Patacamaya by making use of robots that operate on solar energy, Quispe told Reuters. (Photo by David Mercado/Reuters)

West Berliners crowd in front of the Berlin Wall as they watch East German border guards demolish a section of the wall on November 11, 1989. (Photo by Gerard Malie/AFP Photo)

An inmate with a tattoo of Santa Muerte (The Saint of Death) reacts in the Topo Chico prison, during a media tour, in Monterrey, Mexico, February 17, 2016. The director of a prison in northeast Mexico where 49 people died in a riot this week was accused of murder and detained, along with two others, a state prosecutor said on Saturday. (Photo by Daniel Becerril/Reuters)

The Greenland ice sheet is a vast body of ice covering 660,235 sq miles, roughly 80% of the surface of Greenland. It is the second largest ice body in the world, after the Antarctic Ice Sheet. Some scientists predict that climate change may be near a "tipping point" where the entire ice sheet will melt in about 2000 years. If the entire 2,850,000 cubic kilometres (683,751 cu mi) of ice were to melt, it would lead to a global sea level rise of 7.2 m (23.6 ft).

An climber ascends a silo covered in ice in Cedar Falls, Iowa, United States, January 17, 2016. The owners have connected hoses to the top of the silo and spray it with water in winter months to freeze the exterior for climbing. (Photo by Jim Young/Reuters)