According to National Snow & Ice Data Centre, in the last thirty years, scientists have observed a series of unusual ice shelf collapses on the Antarctic Peninsula. Although it is not unusual for ice shelves to calve large icebergs, that process normally takes months to years, as cracks slowly form in the ice. Following a calving, ice shelves generally recover over a period of decades.

In recent years, ice shelves on the Antarctic Peninsula and along the northern coast of Canada have experienced rapid disintegration. In 2004, a scientist concluded that although the remaining Larsen C region, which is the furthest south, appears to be relatively stable for now continued warming could lead to its breakup within the next decade and news reports in summer of 2016 are suggesting that this process has begun.

The Larsen Ice Shelf is a long, fringing ice shelf in the northwest part of the Weddell Sea, extending along the east coast of the Antarctic Peninsula from Cape Longing to the area just southward of Hearst Island. About 350m thick long-running split in the Larson C ice shelf grew suddenly in December and now just 20km of ice is keeping the 5,000 sq. km piece from floating away.

In late August 2016, sunlight returned to the Antarctic Peninsula and unveiled a rift across the Larsen C Ice Shelf that had grown longer and deeper over the austral winter. Satellites spotted it in natural-colour imagery. By November, the arrival of longer days and favourable weather made it possible for scientists to take a closer look.

On November 10, 2016 scientists photographed the growing rift running along the Larsen C ice shelf, showing it running about 70 miles long with a width of more than 300 feet, and a depth of a third of a mile.

By December 2016, the rift had extended to the point where only 20 kilometres (12 miles) of unbroken ice remained and calving was considered to be a certainty in 2017. After calving, the broken fragment will have an area of about 5,000 square kilometres and 350 metres thick, making it among the largest icebergs ever recorded. For comparison, the predicted iceberg’s area is one quarter the size of Wales, or greater than the combined areas of the US states of New Hampshire and Vermont.

The photographs show close and wide views of the rift from the vantage point of NASA’s DC-8 research aircraft. NASA scientist John Sonntag snapped the photos on November 10, 2016, during an Operation IceBridge flight. The mission, which makes airborne surveys of changes in polar ice, completed its eighth consecutive Antarctic deployment later that month.

The rift in Larsen C measures about 100 meters (300 feet) wide and cuts about half a kilometre (one-third of a mile) deep — completely through to the bottom of the ice shelf. While the rift is long and growing longer, it does not yet reach across the entire shelf. When that happens, Larsen C will shed an iceberg about the size of Delaware.

Researchers based in Swansea say the loss of a piece a quarter of the size of Wales will leave the whole shelf vulnerable to future break-up. They have been tracking the rift in Larsen C for many years, watching it with some trepidation after the collapse of Larsen An ice shelf in 1995 and the sudden break-up of the Larsen B shelf in 2002.

‘If it doesn’t go in the next few months, I’ll be amazed,’ project leader Prof Adrian Luckman, from Swansea University, reports BBC.

‘There hasn’t been enough cloud-free Landsat images but we’ve managed to combine a pair of Esa Sentinel-1 radar images to notice this extension, and it’s so close to calving that I think it’s inevitable.’ Prof Luckman says that would put the iceberg among the top 10 biggest that have been recorded.

It is believed that climate warming has brought forward the likely separation of the iceberg but the scientists say they have no direct evidence to support this. However, they are concerned about how any break-off will impact the rest of the ice shelf, given that its neighbour, Larsen B, disintegrated spectacularly in 2002 following a similar large calving event.

‘We are convinced, although others are not, that the remaining ice shelf will be less stable than the present one. We would expect in the ensuing months to years further calving events, and maybe an eventual collapse — but it’s a very hard thing to predict, and our models say it will be less stable; not that it will immediately collapse or anything like that’ said Prof Luckman.

As it floats on the sea, the resulting iceberg from the shelf will not raise sea levels. But if the shelf breaks up even more, it could result in glaciers that flow off the land behind it to speed up their passage towards the ocean. This non-floating ice would have an impact on sea levels.

According to estimates, if all the ice that the Larsen C shelf currently holds back entered the sea, global waters would rise by 10cm.

There are few certainties right now apart from an imminent change to the outline of Antarctica’s icy coast.

‘The eventual consequences might be the ice shelf collapsing in years to decades, even the sea level contribution of this area is not on anybody’s radar; it’s just a big geographical event that will change the landscape there.’ said Prof Luckman.

Cracks and calving of ice from the front of an ice shelf are normal. Shelves are fed by glaciers and ice streams coming from the interior of the continent. They advance into the ocean until a calving event takes place. The shelf front retreats and then advances again. The whole cycle can occur over the span of a few decades.

But calving that happens faster than a shelf can re-advance can mean trouble for an ice shelf. For example, large and frequent calving events at Larsen B proceeded that shelf’s final period of rapid disintegration, which occurred in just six weeks in 2002.

Ice shelves float, so they do not directly contribute to sea level rise. They are important, however, because they buttress land ice and keep it inland. If a shelf disintegrates, glaciers that feed it can flow more quickly out to sea—a process that directly increases sea level.