Radar satellites got their first good look at Antarctica’s new mega iceberg this weekend.
The EU’s Sentinel-1 and the German TerraSAR-X spacecraft both had passes over the 1,290 square kilometers (500 square miles) block, informally named “A74”.
Their sensors showed the mountain was moving fast away from the Brunt Ice Shelf – the floating platform from which it calved on Friday.
The good news is that no disturbance has been felt in the nearby base of the UK.
The Halley research station is located just over 20 km from the fault line, but GPS stations installed around the facility have sustained stability.
“We did not think there would be a reaction simply because the ice around Halley is slightly separated from the area that produced A74; it is not a good way to transfer voltage to the ice under the station.” explains Dr Oliver Marsh of the British Antarctic Survey (BAS).
“Since Friday’s calving, we’ve had a lot more high-precision GPS data measuring centimeter changes across a range of baselines, and none of this shows anything different from what happened before calving,” he told BBC News . .
Halley is currently mot. In part this is because of Covid; very little Antarctic science is currently being undertaken. But it’s also because BAS was waiting to see how the Brunt ice shelf would behave when mountains started calving from the platform.
A74 was the result of several cracks that developed in the Brunt – some over many years, some very recently. Friday’s calving could very well be the first in a series of breakaways during the coming days and weeks.
Of particular interest now is the section of the Brunt west of Halley. It is almost completely cut through several wide gorges and ravines, and is only held in place by a very thin piece of ice pinned to the seabed in a place known as the McDonald Ice Rumples.
If it gives in, there could very well be a reaction near Halley, with the ice under the station at a rapid pace.
But whether this section will really calve is anyone’s guess.
“I do not think there has been a major calving there since Halley was founded in the late 1950s. Smaller pieces came down, but the ice front was a bit further than it is now,” Dr Marsh said.
A small team briefly entered Halley in January and early February to do essential maintenance and to examine the station’s automated instruments, including the spectrophotometer that measures the behavior of the earth’s ozone “hole”.
One of the group’s tasks was to elevate the Brunt’s GPS units on solar power above the fallen snow. Two of them are now traveling with the new mountain as it drifts to sea.
It was indeed the data of these pair that BAS first warned on the calving when they reported that they moved about 100 meters within an hour between 08:00 and 09:00 GMT. Previously, the ice only moved about 8 m per day.
The German TerraSAR-X image (DLR) at the top of this page was obtained in support of the Research Vessel Polarstern, which operates in the region. The ship scientists, led by the Alfred Wegener Institute (AWI), study interactions in Lake Weddell between the ice, the ocean and the atmosphere.
Where exactly is it?
It is on the Brunt Ice Shelf, which is the floating protrusion of glaciers that flowed from the land into the Weddell Sea. On a map, Lake Weddell is the part of Antarctica directly south of the Atlantic Ocean. The Brunt is on the east side of the sea. Like all ice racks, it will calve icebergs regularly. The last major piece to come down in this area was in the early 1970s.
How big is the new mountain just?
It is estimated that it is approximately 1,299 sq km. Greater London is about 1,500 sq km; the Welsh county of Monmouthshire is about 1,300 sq km. It is large anyway, though not as large as the sample A68 mountain that calved in July 2017 from the Larsen C ice shelf on the west side of Lake Weddell. It was originally about 5,800 square miles, but has since shattered into very small pieces.
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