Londoners enjoying the magnificent sight of sun setting perfectly in the middle of London Eye as seen from Greenwich Park in London, England on the warmest day of the year on April 19, 2018. (Photo by London Viewpoints/Rex Features/Shutterstock)

Police officers speak to a woman in Greenwich Park in London, England on April 4, 2020. The Government has announced a lockdown to slow the spread of Coronavirus and reduce pressure on the NHS. (Photo by Alamy Live News)

Women kiss each other as people celebrate outside the Stonewall Inn in the Greenwich Village neighborhood of New York June 26, 2015. The Supreme Court ruled on Friday that the U.S. Constitution provides same-s*x couples the right to marry, handing a historic triumph to the American gay rights movement. (Photo by Eduardo Munoz/Reuters)

A combination photograph shows revelers dressed in "Dia de Muertos" or "Day of the Dead" themes as they pose for photos while taking part in the Greenwich Village Halloween Parade in the Manhattan borough of New York October 31, 2015. (Photo by Carlo Allegri/Reuters)

Heugh Breakwater by Caroline Walker. Winner in the Coastal Views category. (Photo by Caroline Walker/Sea View Photography Competition 2020)

Bradley Hemmings and Jenny Sealey MBE pose for the camera with a Giant Iron Man on the set of Iron Man at the Greenwich and Docklands Festival in St Alfege Park on June 24, 2011 in London, England after they are announced by LOCOG as the Artistic Directors for the Paralympic Games Opening Ceremony. (Photo by Christopher Lee/Getty Images)

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).

The Royal Observatory just announced its Astronomy Photographer Of The Year 2013 winners. Australian photographer Mark Gee was chosen among a thousand amateur and professional photographers around the globe to win the top title. His work is part of an exhibition of the winning photographers, which opened on Sept. 19 at the Royal Observatory Greenwich. The Royal Observatory shared with us the winners and notable mentions of the competition. Their descriptions of the prizewinners can be found below the images.