The Southern Ocean bends to Ultramarine’s bow as we glide alongside A23a, the world’s largest iceberg. It’s so unfathomably massive it looks like land. At 3,900 square kilometres, it’s five times the size of New York City, its chiselled escarpments soaring and sprawling to form an aquamarine coastline, dotted with albatrosses. This frosty colossus snapped off Antarctica’s Filchner-Ronne Ice Shelf in 1986 but only broke from the seafloor in 2020 – and it’s been on the move ever since.
“Right now, A23a is being taken by the current,” says Yvonne Cook, Quark Expeditions’ glaciologist. “It’s being pushed to the northeast of the Antarctic continent, towards
