(The iceberg broke up in 2006, and the colony of 1,400 breeding pairs is now recovering robustly).
The iceberg broke off the Ross Ice Shelf, a vast floating carpet of ice on the continent's west side.
It had entered the cracks of an iceberg and frozen there, and, when the iceberg broke up, the clear ice had floated away on the seawater.
Mr. Lazzara said that as the larger iceberg broke off, it apparently hit the ice sheet, causing the second berg to form.
The Ice Centre added to concerns over global warming by reporting on Monday that a monster iceberg broke off in the past weeks from the Thwaites ice tongue into the southern Amundsen Sea.
The part of the Ross Ice Shelf where the iceberg broke away is now the same smaller size it was when the explorers Robert F. Scott and Ernest Shackleton observed it at the start of the 20th century.
For the iceberg, this is not the case, as the outward wave when the time derivative is taken of the emerging iceberg is located only where the iceberg breaks the surface, that is, at the edge of the iceberg.
It replaces the amount of ice each year that is lost by icebergs' breaking off and floating down Lago Argentino.
Icebergs breaking off into the ocean at the mouth of glaciers, and extra ice flowing into floating ice shelves, will return much of the increased snowfall to the sea.
