The British Antarctic Survey’s Halley VI research station will shut down for the second winter in a row due to growing cracks in the ice sheet where it sits, reports Nicola Davis at The Guardian.

The decision was made based on satellite data of two cracks that are active on the Brunt Ice Shelf floating over the Weddell Sea. One is a crack that was dormant for 30 years before it began to spider northward in 2012, quickening its rate over the last seven months. The other is currently over 30 miles long, and has been dubbed “The Halloween Crack” since it first appeared in October 2016. It has since crossed the resupply trail for the research station. Seventy people typically work at the remote base in the summer and 14 hang on for the long, cold winter. But the appearance of the cracks has forced the station to shutter its doors between March and November of 2018.

“The safety of our staff is our priority in these circumstances,” Jane Francis, director of the British Antarctica Survey tells Davis. “Because access to the station by ship or aircraft is extremely difficult during the winter months of 24-hour darkness, extremely low temperatures and the frozen sea, we will once again take the precaution of shutting down the station before the 2018 Antarctic winter begins.”

As Jonathan Amos at the BBC reports, in February the research station was moved 14 miles inland on the ice shelf to ensure it was not on the wrong side of the cracks if they continued to extend. But at this point, the station will stay put. “We are not going to move the station any further—we believe that the station is actually in the optimal place on the ice shelf now,” David Vaughn, British Antarctic Survey's director of science tells Davis.

This isn’t the first time that the moving ice has interfered with the research station. And it definitely won't be the last. Since 1956, the BAS has had a permanent presence on the Brunt ice shelf, beginning with the Halley I station. As the ice shelf has calved icebergs into the sea and slowly spread out toward the Antarctic ocean, the stations moved with it, becoming uninhabitable. In 2012, Halley VI was deployed, a modular station on legs and skis that looks like a futuristic train. Because the ice shelf moves at least a quarter mile toward the ocean each year, the skis allow the researchers to occasionally reposition the station. The legs allow the Halley VI to be raised above the snow, which eventually engulfed its predecessors.

According to a press release, over the decades the Halley station has played a key role in collecting climate and weather data as well as detecting the hole in the ozone layer. In recent years, researchers at the station have studied solar radiation and its impacts on Earth. The winter closures disrupt that continuous sampling, so Amos reports, the researchers are hoping to get a kerosene generator up and running that will be able to keep automated instruments going throughout the winter, though Vaughn says the system is just a prototype and may not be able to withstand the snow, sub-zero temperatures and strong winds.

It’s almost inevitable that a big chunk of the ice shelf will calve off, though the researchers are fairly certain the Halley Station is currently in a safe spot. “Eventually we expect the ice from [the previous site] to part company with the ice shelf and float off as an iceberg – but the question is essentially when is that going to happen, and whether there would be other changes in the ice shelf that we haven’t predicted that would [result],” Vaugn tells Davis.

The researchers don’t believe the calving is caused by climate change. Instead, in a recent study in the journal The Cryosphere, researchers suggest that an area of the shelf called the McDonald Ice Rumples are buttressing the ice sheet. If the cracks interact with that area, it could rapidly speed up ice calving on the shelf, similar to an event that took place in the 1970s.