The recent rapid retreat of an Antarctic glacier could be unprecedented, a new study suggests, a finding which could have major implications for future sea-level rise.
The researchers found that Hektoria Glacier retreated by more than 8km (5 miles) in just two months in late 2022.
The authors believe it could be the first modern example of a process where the front of a glacier resting on the seabed rapidly destabilises. 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 unraveling the causes is like a 'whodunnit' mystery, according to study lead author Naomi Ochwat, research affiliate at the University of Colorado Boulder and post-doctoral researcher at the University of Innsbruck.
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. But the bay vacated by the ice shelf was eventually filled with sea-ice 'fastened' to the seabed, helping to partly stabilise Hektoria. That was until early 2022, when the sea-ice broke up.
What followed was further loss of floating ice from the front of Hektoria, as large, flat-topped icebergs broke off or 'calved', and the ice behind sped up and thinned.
This extraordinary change, the authors say, could be thanks to an ice plain - a relatively flat area of bedrock on which the glacier lightly rests. Upward forces from the ocean water could 'lift' the thinning ice essentially all at once, they argue - causing icebergs to break off and the glacier to retreat in quick time.
'Glaciers don't usually retreat this fast,' said co-author Adrian Luckman, professor of geography at Swansea University. 'The circumstances may be a little particular, but this rapid retreat shows us what may happen elsewhere in Antarctica where glaciers are lightly grounded, and sea-ice loses its grip,' he added.
But other researchers have contested the study's findings. The controversy surrounds the position of the 'grounding line' or 'grounding zone' - where the glacier loses contact with the seabed and starts to float in the ocean. Dr. Frazer Christie, glaciologist, stated that the precise location of Hektoria Glacier's grounding line was difficult to ascertain, making the study’s conclusions uncertain.
Overall, while there is disagreement over the specifics of Hektoria's retreat, the urgency to monitor and understand the swift changes occurring in Antarctica is universally acknowledged by scientists.
The researchers found that Hektoria Glacier retreated by more than 8km (5 miles) in just two months in late 2022.
The authors believe it could be the first modern example of a process where the front of a glacier resting on the seabed rapidly destabilises. 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 unraveling the causes is like a 'whodunnit' mystery, according to study lead author Naomi Ochwat, research affiliate at the University of Colorado Boulder and post-doctoral researcher at the University of Innsbruck.
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. But the bay vacated by the ice shelf was eventually filled with sea-ice 'fastened' to the seabed, helping to partly stabilise Hektoria. That was until early 2022, when the sea-ice broke up.
What followed was further loss of floating ice from the front of Hektoria, as large, flat-topped icebergs broke off or 'calved', and the ice behind sped up and thinned.
This extraordinary change, the authors say, could be thanks to an ice plain - a relatively flat area of bedrock on which the glacier lightly rests. Upward forces from the ocean water could 'lift' the thinning ice essentially all at once, they argue - causing icebergs to break off and the glacier to retreat in quick time.
'Glaciers don't usually retreat this fast,' said co-author Adrian Luckman, professor of geography at Swansea University. 'The circumstances may be a little particular, but this rapid retreat shows us what may happen elsewhere in Antarctica where glaciers are lightly grounded, and sea-ice loses its grip,' he added.
But other researchers have contested the study's findings. The controversy surrounds the position of the 'grounding line' or 'grounding zone' - where the glacier loses contact with the seabed and starts to float in the ocean. Dr. Frazer Christie, glaciologist, stated that the precise location of Hektoria Glacier's grounding line was difficult to ascertain, making the study’s conclusions uncertain.
Overall, while there is disagreement over the specifics of Hektoria's retreat, the urgency to monitor and understand the swift changes occurring in Antarctica is universally acknowledged by scientists.
