Life on a floating ice shelf is precarious enough, but when a massive crack is heading your way, you know you鈥檙e in trouble. This nightmare scenario is what鈥檚 forcing the UK鈥檚 newest research station in Antarctica to relocate.
Halley VI opened in 2013 to much fanfare due to its space-age design. It鈥檚 built as eight modules on skisso that it can be towed to a new location if the ice conditions change.
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The British Antarctic Survey (BAS) research station has been gathering atmospheric data since 1956 鈥� measurements from Halley led to the discovery of the hole in the ozone layer in 1985. It is located on the Brunt ice shelf, a floating slab of ice some 150 to 250 metres thick attached to the Antarctic landmass and extending out into the sea.
All five of Halley鈥檚 predecessors had to be abandoned after becoming buried in the snow or getting too close to the edge of the shelf. But the threat now facing Halley VI is different.
Ice shelves commonly feature crevasses. Extremely large cracks occasionally form when the shelf breaks in the summer but then partially heal in the winter as the sea freezes and snow accumulates. These cracks sometimes begin to grow again, which can lead to vast icebergs breaking off into the ocean.
This happened in 1998, when a huge section of the nearby Filchner-Ronne ice shelf broke off, creating a massive iceberg 144 kilometres long and 48 km wide with the unoccupied German base Filchner trapped on top. And in 2013, a massive iceberg roughly the size of New York City calved off at Pine Island Glacier on the opposite side of the Antarctic.
鈥淎ll ice shelves do this. It鈥檚 a natural event,鈥� says Hilmar Gudmundsson, a glaciologist at the BAS. 鈥淏ut it鈥檚 difficult to say exactly when and how large these events will be. It鈥檚 a bit like trying to predict an earthquake.鈥�
The Brunt ice shelf has a number of prominent cracks, including one called Chasm 1. It鈥檚 a massive feature 鈥� more than 50 m deep, 30 km long and 1 km wide in parts 鈥� that formed 30 years ago but remained dormant. Then, in 2012, the area round the tip of the chasm began to change and satellite measurements confirmed that the crack had started to grow. It鈥檚 not clear why this happened, but Gudmundsson says there is no evidence that it is related to global warming.
The crack is extending in the direction of Halley VI at a rate of 1.7 km a year, and is 8 km away from the base. 鈥淲e don鈥檛 know what will happen,鈥� says Gudmundsson. 鈥淚t might stop growing, but we can鈥檛 exclude the possibility of a big calving event.鈥�
The main concern is that Chasm 1 will grow so much that it makes it impossible to relocate the base in the future. That鈥檚 why a move is now underway.
The station has recently began its brief summer season after nine months of winter isolation, and during this time, preparations will be made for the move. The bulldozers needed to tow the modules will be brought in by ship in the coming months 鈥� assuming it can get through the heavy sea ice common here. If all goes to plan, the relocation will take place in a year鈥檚 time.
鈥淲e鈥檒l break down the base into individual modules and each will be towed to a new site. That鈥檚 the simplistic version anyway,鈥� says Adam Bradley, Halley鈥檚 station leader. The move is going to be complex and costly, with many technical challenges. For example, the modules are so heavy that even small slopes pose an issue, so the route must be carefully chosen. 鈥淥ne of the jobs is to define the maximum slope angle that we can tow these things up,鈥� Bradley says.
The exact location of Halley VI鈥檚 new home will be decided in a few months after extensive surveys of the terrain have taken place, but it will be on the other side of Chasm 1, perhaps 20 to 30 km away.
鈥淭hat gets us into a safer zone,鈥� says Bradley. But this site will bring new logistical challenges, as it鈥檚 further from the coast and all supplies arrive by ship.
Until the base can be moved, however, Gudmundsson will be keeping a close eye on Chasm 1, via satellite images and GPS.
Read more: 鈥�Zeros to heroes: How we almost missed the ozone hole鈥�; 鈥�Driller thriller: Antarctica鈥檚 tumultuous past revealed鈥�
Image credits from top: Antony Dubber, British Antarctic Survey; Tom Welsh
This article appeared in print under the headline 鈥淗uge crack forces early move for Antarctic base鈥�
