Radar satellites took their first good look at Antarctica’s new mega-iceberg over the weekend.
The EU Sentinel-1 spacecraft and Germany’s TerraSAR-X spacecraft passed over the 1,290 km2 (500 square miles) block, informally called “A74”.
Its sensors showed that the iceberg moved away quickly from the Brunt ice shelf – the floating platform it left on Friday.
The good news is that no disturbance was felt at the neighboring UK base.
The Halley research station is located just over 20 km from the fracture line, but the GPS stations installed around the facility have reported continued stability.
“We don’t think there would be a reaction simply because, glacologically speaking, the ice around Halley is slightly separated from the area that produced A74; there is no good way for stress to be transmitted to the ice under the station.” explained Dr. Oliver Marsh of the British Antarctic Survey (BAS).
“Since giving birth on Friday, we have had a lot more high-precision GPS data that measures centimeter changes in voltage across a range of baselines, and none of them show anything different from what was happening before giving birth,” he told BBC News. .
Halley is currently disabled. In part, this is because of Covid; very little Antarctic science is currently being developed. But it’s also because BAS is waiting to see how Brunt’s ice shelf will behave when icebergs start to form on the platform.
A74 was the result of multiple cracks that developed at Brunt – some over many years, others very recently. Friday’s birth may well be the first in a series of breakouts over the next few days and weeks.
Of particular interest now is the Brunt section west of Halley. It is almost entirely cut by several chasms and wide crevices, and is only held in place by a piece of very thin ice that is attached to the seabed in a place known as McDonald Ice Rumples.
If that gives way, there may well be a reaction near Halley, with the ice under the station moving towards the sea at an accelerated rate.
But if this section is really going to give birth, nobody knows.
“I don’t think there has been a big birth there since Halley was created in the late 1950s. Smaller pieces came out, but the ice front was much further back than it is now,” said Dr. Marsh.
A small team briefly went to Halley in January and early February to do essential maintenance and check the station’s automated instruments, including its spectrophotometer that measures the behavior of the Earth’s ozone “hole”.
One of the group’s tasks was to lift the Brunt’s solar-powered GPS units above fallen snow. Two of them now travel with the new iceberg as it travels out to sea.
In fact, it was this pair’s data that first alerted BAS about childbirth on Friday, when they reported that their positions moved about 100m in an hour between 08:00 and 09:00 GMT. Previously, the ice moved only about 8 m a day.
The image of the German space agency (DLR) TerraSAR-X at the top of this page was acquired in support of the Polarstern Research Ship, which is operating in the region. The ship’s scientists, led by the Alfred Wegener Institute (AWI), are studying interactions in the Weddell Sea between the ice, the ocean and the atmosphere.
Where exactly is this?
It is on the Brunt ice shelf, which is the floating ledge of the glaciers that flowed from the land into the Weddell Sea. On a map, the Weddell Sea is that sector of Antarctica directly south of the Atlantic Ocean. The Brunt is on the east side of the sea. Like all ice platforms, it periodically creates icebergs. The last big piece to come out in this area was in the early 1970s.
How big is the new iceberg?
Estimates point to about 1,290 km2. Greater London is about 1,500 km2; the Welsh county of Monmouthshire covers approximately 1,300 km2. This is big by any measure, although not as big as the A68 iceberg monster, which gave birth in July 2017 on the Larsen C ice shelf on the west side of the Weddell Sea. This was originally about 5,800 square kilometers, but has since broken into many small pieces.
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