NASA satellite images show two cracks running across the Antarctic Brunt Ice Shelf which could break off and create a 1,700 km-iceberg.
The rift, known as the 'Halloween crack' first appeared in October 2016, and is spreading to the east. It is set to meet another fissure that had been stable for 35 years but is now accelerating north at a rate of 2.5 miles a year.
Once that happens, the shelf will release an iceberg measuring approximately 660 square miles (1,700 square km), larger than all of London's boroughs combined (607 miles squared) and twice the size of New York. This is likely to happen in a matter of weeks and it will be the biggest iceberg to separate from the Brunt Ice Shelf since 1915.
Depending on where the cracks merge, the stability of the entire shelf could be jeopardised, Joe MacGregor, a glaciologist at NASA's Goddard Space Flight Centre told Earth Observatory: "If the [cracks] merge upstream (south) of the McDonald Ice Rumples, then it's possible that the ice shelf will be destabilised."
Impacts of climate change
Impacts of climate change
Flooding on the pitch at Brunton Park, home of Carlisle United Football Club. Record rain fall in Cumbria caused flooding to several areas of Carlisle, causing houses to be evacuated by emergency services. (Photo by Colin McPherson/Corbis via Getty Images)
Disappearing coast caused by rising sea levels Happisburg Norfolk UK. (Photo by: Avalon/UIG via Getty Images)
CUMBRIA, UNITED KINGDOM - DECEMBER 10: Acres of farmland seen completely submerged in flood waters in the Lyth Valley, near levens on December 10, 2015 in Cumbria, England.
Storm Desmond crashed into the UK, producing the UK's highest ever 24 hour rainfall total at 341.4mm. It flooded the Lyth Valley, drowning many farms and houses. Several periods of subsequent heavy rain have kept the Lyth Valley inundated, with no sign of respite.
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Canada, Nunavut Territory, Repulse Bay, Polar Bear (Ursus maritimus) swimming past melting iceberg near Harbour Islands
A flooded bank of the Seine in front of the Alexander III bridge on January 26, 2018, as the River Seine, which runs through the French capital Paris, is expected to reach a peak of up to 6.2 metres (20.3 feet) on a scale used to measure its levels by January 27, making it four to five metres above its normal height. The Seine continued its relentless rise flooding quays with muddy water and putting museums on an emergency footing as record rainfall pushed rivers over their banks across northeastern France. (Photo by Michel Stoupak/NurPhoto/Sipa USA)
Locals point to the bridge in Tadcaster, North Yorkshire, which has collapsed following recent flooding, as Storm Frank begins to batter the UK on its way towards flood-hit areas.
Bees gather on a hive in Merango, Illinois, U.S., on Monday, Sept. 10, 2018. Beekeepers in the U.S. reported an increase in honeybee deaths over the last year, possibly the result of erratic weather patterns brought on by a changing climate. Photographer: Daniel Acker/Bloomberg via Getty Images
Dead coral reefs in shallow water which were killed during the mass coral bleaching event, which is relating to climate change. Bleaching of coral colonies is caused by warming of sea temperature and most likely combined with other environmental stresses causing coral to expel symbiotic zooxanthellae algae, which could even lead to coral death.
A protest in the Osney area of Oxford claiming climate change is to blame for the floods ravaging the country this summer.
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The long-term future of Antarctic ice shelves will have an important influence on sea level rise around the globe. A report released by scientists last year stated that Antarctic ice is melting at a record-breaking rate, accelerating threefold in the last five years, and now poses a major threat to coastal cities.
Unless there are major reductions greenhouse gas emissions, scientists say that Antarctica's melting ice should add more than 25cm to total global sea level rise by 2070.