When an Antarctic glacier was sparked into rapid retreat three years ago, it left scientists scratching their heads as to what might have caused it.
Hektoria Glacier retreated by more than 8km (5 miles) in just two months in late 2022 - and now a new study claims to have the answer.
The authors believe that Hektoria could be the first modern example of a process where the front of a glacier resting on the seabed rapidly destabilizes. That could lead to much faster sea-level rise if it happened elsewhere in Antarctica, they say.
But other scientists argue that this part of the glacier was actually floating in the ocean – so while the changes are impressive, they are not so unusual.
Floating tongues of glaciers extending into the sea – called ice shelves – are much more prone to breaking up than glacier fronts resting on the seabed.
That Hektoria has undergone huge change is not contested. Its front retreated by about 25km (16 miles) between January 2022 and March 2023, satellite data shows.
But unravelling the causes is like a 'whodunnit' mystery, according to study lead author Naomi Ochwat, research affiliate at the University of Colorado Boulder.
The case began way back in 2002 with the extraordinary collapse of an ice shelf called Larsen B in the eastern Antarctic Peninsula. About 3250 sq km (1250 sq miles) of ice shelf was lost, roughly the size of Cambridgeshire or Gloucestershire.
Larsen B had been effectively holding Hektoria Glacier back. Without it, Hektoria's movement sped up and the glacier thinned. That was until early 2022, when the sea-ice broke up.
Following this, further loss of floating ice from the front of Hektoria led to large, flat-topped icebergs breaking off or 'calving'. But the unprecedented nature of the retreat suggests that the front of the glacier was resting on the seabed rather than floating at one point.
This extraordinary change could be attributed to an ice plain, according to the study. This has never been observed in the modern world, but similar markings on the seafloor hint it may have triggered rapid ice loss in the Earth's past.
The implications are dire, as such processes could escalate the rate of sea-level rise, especially if similar phenomena occur in larger glaciers like the infamous Thwaites.
Despite assertions from fellow scientists contesting the study’s interpretation of the glacier's grounding line, the need for data and monitoring remains critical to fully understand these changes and their ramifications for sea levels.
