Petermann's 30-square-mile calving was the small one: two bigger sections are already cracked

The number neither release prints is the size of the thing being subtracted from. Both give the output instead: three calvings totalling roughly 254 square kilometres, trimming the floating tongue by about 22 percent ^[13]. Read that percentage against the tongue as it stood before Aug. 4 and the tongue was around 1,155 square kilometres, with about 1,078 left now ^[1]. The event that got reported was therefore about 6.6 percent of it ^[2], and the lesser part of what the University of Ottawa team says is queued: the two sections still attached, at 94 and 84 square kilometres ^[11], come to 178 square kilometres, roughly 2.3 times the area that left on Aug. 4 ^[3]. The three figures sum to 254.4, so the published total and the published percentage are internally consistent ^[8].

Thickness differs between the two write-ups only in units. The uOttawa release puts the island at as much as 150 metres ^[6]; Discover says up to 500 feet ^[7], which is the same measurement rounded ^[5]. Treat 150 metres as an upper bound across the whole slab and the island carries on the order of 11 cubic kilometres of ice ^[4], a ceiling rather than a measurement, since the sources give no thickness field.

The detection chain is the part worth keeping. Sentinel-1 showed deterioration along the tongue's centreline on Aug. 3, and by 20:00 UTC on Aug. 4 the island had separated from the eastern side ^[4]. That was not the first warning: in April 2026, researchers stacked radar passes using interferometry and saw deformation and spreading fractures, according to NASA ^[8], about four months of lead on the break itself ^[6]. "We've anticipated this break for years, and seeing it finally happen is remarkable," said Adam Garbo, the uOttawa doctoral student who identified the event ^[10][9].

The comparison figures deserve a caveat the releases do not attach. The team's systematic Sentinel-1 record of the tongue starts in 2019 ^[9], so "largest since 2012" reaches seven years behind the start of their own monitoring ^[10]. Petermann's earlier large breaks came in 2008, 2010 and 2012 ^[18], meaning the quiet interval before this one ran 14 years ^[7]. Discover's framing is that the August event could have passed almost unnoticed without Copernicus Sentinel-1 ^[3], whose radar images through cloud and darkness ^[5]. The public description arrived 22 days after separation, in a release dated Aug. 26 ^[9][20].

Then there is the object itself, drifting out of a tongue that extends into Nares Strait ^[19]. "These are thick blocks of ice that can drift for years," said Abigail Dalton of the Canadian Ice Service, adding that they fracture into smaller, harder-to-track pieces that threaten vessels and resource operations ^[15]. Environment and Climate Change Canada is monitoring its movement and assessing risk to shipping and offshore infrastructure, as it has after previous Arctic ice shelf calvings ^[14]. Anna Crawford of the University of Stirling notes that tabular bergs this size are common around Antarctica and rare in the Arctic ^[16], which is the case for spending observation time on it: what it teaches about calving and deterioration transfers to glacier dynamics, sea-level rise and ocean conditions elsewhere ^[17].