Behold A-74, an enormous iceberg that broke away from the Brunt Ice Shelf in Antarctica late last month. Here’s what we know about the new ‘berg and what could happen next.
Scientists with the British Antarctic Survey reported the birth of the new iceberg on February 26, which they detected with GPS equipment. Christopher Readinger, an ice analyst with the U.S. National Ice Centre, confirmed the iceberg on the following day by analysing satellite photos snapped by Sentinel-1A. The USNIC named the iceberg “A-74,” using a naming convention in which icebergs are named according to the Antarctic quadrant in which they were originally spotted.
A-74 broke off from the Brunt Ice Shelf northeast of the McDonald Ice Rumples, a region characterised by crevasses and rifts produced by an underwater formation that blocks the flow of ice, according to NASA’s Earth Observatory. A prominent feature, known as the Halloween Crack, still cuts into the ice shelf, which it has done since 2016, per the European Space Agency.
At 1,270 square kilometres in size, A-74 is pretty big. That’s about 20 times the size of Manhattan. By comparison, the late, great iceberg A-68 — now a shattered mess off the coast of South Georgia island — was nearly five times bigger when it calved from Antarctica’s Larsen C Ice Shelf in 2017.
That the Brunt Ice Shelf would produce an iceberg of such enormity is not a huge surprise, as BAS glaciologists have been monitoring the area — and documenting various cracks and chasms — for the past couple of years. That said, this is the first major calving of the Brunt Ice Shelf since 1971, according to the European Space Agency. While climate change is driving an increasingly rapid drop in Antarctica’s ice by melting it from above and below, this calving event is likely the result of natural processes playing out.
A-74 is now a free-floating iceberg, but it hasn’t done much with its newfound freedom. Pierre Markuse, a remote sensing expert, said “nothing really new has happened” since the iceberg broke away, and it’s “still very very close to the ice shelf.” Some edges appear to be “crumbling a bit, but nothing major so far,” he explained in a Twitter DM. The lack of movement is making it difficult to predict where A-74 might eventually wander, but scientists have a general sense of the scenarios that could play out.
“Over the following weeks and months, the iceberg could be entrained in the swift southwesterly flowing coastal current, run aground, or cause further damage by bumping into the southern Brunt Ice Shelf.” Mark Drinkwater, an ESA cryospheric remote sensing expert, explained in a statement. “So we will be carefully monitoring the situation using data provided by the Copernicus Sentinel-1 mission.”
A-74 could eventually drift into the Weddell Gyre (which is what happened to A-68), and from there drift far enough north into the Antarctic Circumpolar Current. This will be of relevance to the shipping industry, as the iceberg could produce a dangerous number of fledgling icebergs over the coming months and years.
We’ll be watching.