In July 2017, a trillion-ton iceberg (designated A68) the size of Delaware broke off from Antarctica’s Larsen C ice shelf, creating one of the largest recorded icebergs and reducing the ice shelf by 12%. The calving followed decades of warming on the Antarctic Peninsula (the fastest-warming region on the continent) and the earlier collapses of Larsen A (1995) and Larsen B (2002). While iceberg calving is natural, the scale and frequency of Larsen ice shelf disintegrations raised concerns about Antarctica’s stability and its contribution to sea level rise as warming accelerates ice sheet losses.

The Calving Event

Scientists tracked a growing rift in Larsen C since 2010, watching it extend across the ice shelf at accelerating rates. In July 2017, the rift finally severed completely, releasing an iceberg 5,800 sq km in area and 200+ meters thick. The iceberg drifted north into the South Atlantic, slowly fragmenting over subsequent years. Because the Larsen C ice shelf was already floating (displacing its weight in water), the calving itself didn’t raise sea levels—the concern was what happens next: without ice shelf buttressing, land-based glaciers behind Larsen C could flow faster into the ocean, contributing to sea level rise.

Ice Shelf Collapse Precedents

Larsen A ice shelf disintegrated in 1995, followed by Larsen B’s dramatic collapse in 2002 (shattering into thousands of icebergs over weeks). Post-collapse, glaciers previously held back by these ice shelves accelerated 2-8 times their original speeds, contributing to sea level rise. The pattern suggested ice shelves act as critical “corks” slowing glacier flow; once removed, glaciers speed up. Larsen C’s 2017 calving didn’t trigger immediate collapse, but scientists monitored for signs of accelerated weakening.

Climate Change Attribution

The Antarctic Peninsula warmed ~3°C over the 20th century (far above global averages), driven by changing atmospheric and ocean circulation patterns linked to human-caused climate change. Warmer air temperatures melted ice shelf surfaces, creating meltwater that trickled into crevasses, widening them (meltwater expansion as it refreezes can fracture ice). Warmer ocean currents eroded ice shelves from below. While individual calving events aren’t directly attributable to climate change, the multi-decade trend of ice shelf thinning, rift expansion, and collapses aligns with warming predictions.

A68’s Journey

Iceberg A68 became a minor celebrity, tracked by satellites as it drifted north toward South Georgia island (threatening penguin and seal colonies if it grounded and blocked their feeding routes). By 2020, A68 fragmented into smaller icebergs (A68a, A68b, etc.), which eventually melted in warmer waters by 2021. The brief existence of one of Earth’s largest icebergs symbolized Antarctica’s changing dynamics under a warming climate.

Sources: European Space Agency Sentinel satellite imagery (July 2017), British Antarctic Survey press releases, Nature Climate Change Antarctic ice shelf research, NASA ICESat-2 ice monitoring