The British Antarctic Survey closed its Halley base for another winter.
The team left the station, leaving about 80% of the experiments they would normally do during the polar night operating on automatic.
The closure is the result of constant uncertainty about the stability of the ice near Halley, which is likely to break at sea.
BAS believes the base is far enough away not to be affected, but does not want people to be there just in case.
Sending airplanes to evacuate personnel in the dark of winter and in bad weather is an unnecessary risk.
This is the third winter on the trot now that Halley has been closed.
The base is on the Brunt ice shelf – the floating protrusion of the glaciers that flow from the Antarctic into the Weddell Sea.
Periodically, this platform will receive icebergs and there is currently a large opening that will create a particularly large block – roughly the size of Greater London.
But when that happens, no one can say.
"What really matters is what happens upstream of the abyss where Halley is located," explained BAS chief scientific officer David Vaughan.
"We have a network of about 15 GPS stations across the ice shelf around Halley, and their data is transmitted to us every day with a day late. And although, yes, by the crack, there are changes – by Halley, we actually saw very little ice deformation, "he told BBC News.
There has been a permanent research station at Brunt since the late 1950s. The buildings underwent several upgrades with the latest installation with legs and skis. This allows the entire segmented structure to be moved.
In 2017, BAS tractors dragged the base 23 km from the water's edge to put it in a safer place. It was a smart move, because without the relocation, Halley would now be sitting on the wrong side of the abyss.
Glaciologists continue to use satellite images of the region to monitor the behavior of the abyss. The situation has been somewhat complicated by the appearance of an additional fissure, dubbed the Halloween Crack, which moves in a different direction.
The way events unfold will largely depend on what happens in a shallow water area known as the McDonald Ice Rumples.
This collision at the bottom of the Weddell Sea acts as a fixation point that retains and stabilizes the 150m thick Brunt shelf. Just where the abyss breaks the rumples – and it has about 4.5 km to go – will almost certainly influence the upstream ice reaction.
Halley is extremely important to BAS activities.
In addition to serving as a launching pad for deep-sea Antarctic incursions, it gathers essential weather and climate data.
Famously, it played a critical role in research that identified the ozone "hole" in 1985, and in recent years has also become an important center for the study of solar activity and the impacts it has on Earth.
The research team has worked hard to try to keep the observations, even if they themselves are not present.
An important solution is the installation of a micro-turbine – a kind of "jet engine in a box". This is providing the power for automated instrumentation, including the Dobson photodetecograph that keeps an eye on the ozone layer.
Conducting experiments in Antarctica without people is a challenge because of the adverse conditions.
If the micro-turbine air intake is blocked with snow or ice, and no one is around to remove the obstruction, the machine will shut down and the instruments will be offline.
But the jet engine has been running without incident for several weeks, and Professor Vaughan believes that if the system proves its capacity, it can become a very useful technology in other places in Antarctica.
"We can use it in the field in places where it is too difficult or too expensive to go through wintering seasons these days," he said.
"Halley's a good test. It's not an easy place to operate."
People will return to the base when sunlight begins to return in the polar south around October / November.
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