Giant iceberg breaks off in front of UK station

In front of the Brunt Ice Shelf

An archive photograph of the broken leading edge of the ice

A large iceberg roughly the size of Greater London broke off from Antarctica near England’s Halley research station.

Sensors on the surface of the Brunt Ice Shelf confirmed the split late Sunday GMT.

At Halley, 21 staff currently maintain the base and operate its scientific instruments.

They are not in any danger and will continue their work until they are picked up early next month.

The British Antarctic Survey (BAS) operates the station in a reduced role in anticipation of calving.

Halley is located about 15 km from the fracture line.

BAS has a number of GPS devices that transmit information about ice movements in the area back to the agency’s headquarters in Cambridge.

Halley

Britain has had a research station on the Brunt Ice Shelf since 1957.

Authorities will review the satellite imagery as it becomes available. They will want to see that unexpected instabilities do not arise on the remaining ice shelf platform holding Halley.

A similarly sized iceberg known as A74 calved further east in February 2021. At the time, it was thought that his breakup could initiate the latest breakup, but these events are beyond any precise guess.

Antarctica region map

Antarctica region map

Where exactly is this place?

It is on the Brunt Ice Shelf, a floating outcrop of glaciers that flows from the Antarctic continent to the Weddell Sea. On a map, the Weddell Sea is the portion of Antarctica directly south of the Atlantic Ocean. Brunt is on the east side of the sea. Like all ice shelves, it will periodically ice the icebergs. This is the last iceberg, and before the A74, the last major piece to come out of Brunt was in 1971.

Was escape expected?

Absolutely. It’s not just the timing. Scientists are constantly watching for any major rift in Brunt and have noticed that a particular rift – dubbed Abyss One – is starting to reopen after decades of dormancy. Recent years have seen the expansion of Abyss One accelerate, resulting in the complete separation of a block of ice now about 150-200 m thick.

Abyss One

Cliff One is the main fracture line running along the ice shelf.

What now for Halley station?

The British base consists of a series of modules on skis that allow it to be transported away from the front edge of the ice shelf. When Chasm One was seen coming back to life, the decision was made to shift Halley 23km “upstream” – this mission was completed in early 2017. Had this displacement not taken place, Halley would now be sitting in a very dangerous position in separation. iceberg.

What about the people in the region?

During the Antarctic winters, BAS was removing all its personnel from Halley. He didn’t want to have to evacuate people at a time of year when the polar night lasted 24 hours and the weather conditions could be terrible. This can be done quickly and safely if the Austral post, i.e. the small crew currently on station, needs to be removed.

How big is the new iceberg?

Estimates suggest it’s about 1,550km² – about 600 square miles. This is great in every way. It’s the size of a city. The job of naming the icebergs falls to the US National Ice Center. Because the new block is in the Antarctic quadrant extending from 0 degrees longitude to 90 degrees West, it will bear the letter “A” in its designation. It is likely to be called the A81. “81” refers to its place in the major calving sequence in the region. The similar-sized iceberg that split off from Brunt east of Halley was called A74.

McDonald's Ice Flaps

McDonald Ice Rumples helped fix and stabilize the ice

What happens next?

Calving large icebergs from a shelf structure can cause an acceleration in ice flow. Before calving, Brunt was flowing westward at a rate of about 3m/day. If it experiences an acceleration now, it could affect the behavior of other cracks in that area. In particular, scientists are watching very closely a crack they call Halloween Crack. It is located north and east of Halley and radiates away from the base. Researchers will want to observe his reaction, if any. Much will depend on what will be called McDonald’s Ice Rumples, a so-called raised seafloor area that grabs the underside of the Brunt rack and normally helps it snap into place.

Is this climate change in action?

No. Calving icebergs at the front edge of an ice shelf is a very natural behavior. The shelf likes to maintain a balance, and the ejection of icebergs is a way to balance the accumulation of snowfall and the influx of more ice feeding land glaciers. Unlike the Antarctic Peninsula on the other side of the Weddell Sea, the scientists did not detect climatic changes in the Brunt region that would significantly alter the natural process described above. What’s more, estimates suggest that Brunt reached its greatest size at least 100 years before birth. Famed explorer Sir Ernest Shackleton recorded a much smaller shelf structure when the ill-fated Imperial Trans-Antarctic Expedition passed by in 1914-1917. It was definitely time for an important calving.

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