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 destabilises. 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's because they can be more easily eaten away by warm water underneath.
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 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. However, 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. That is not unusual. Iceberg calving is a natural part of ice sheet behaviour, even though human-caused climate change makes the loss of ice shelves much more likely. What was unprecedented, the authors argue, was what happened in late 2022, when they suggest the front of the glacier was grounded - resting on the seabed - rather than floating.
In just two months, Hektoria retreated by 8.2km. That would be nearly ten times faster than any grounded glacier recorded before, according to the study, published in Nature Geoscience. 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.
Scientists stress that while the situation at Hektoria underscores the sensitivity of Antarctic glaciers, more data and observations are crucial to discern patterns that could affect global sea levels in the future.
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's because they can be more easily eaten away by warm water underneath.
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 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. However, 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. That is not unusual. Iceberg calving is a natural part of ice sheet behaviour, even though human-caused climate change makes the loss of ice shelves much more likely. What was unprecedented, the authors argue, was what happened in late 2022, when they suggest the front of the glacier was grounded - resting on the seabed - rather than floating.
In just two months, Hektoria retreated by 8.2km. That would be nearly ten times faster than any grounded glacier recorded before, according to the study, published in Nature Geoscience. 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.
Scientists stress that while the situation at Hektoria underscores the sensitivity of Antarctic glaciers, more data and observations are crucial to discern patterns that could affect global sea levels in the future.
