An Antarctic glacier’s astonishingly rapid retreat, occurring over just two months in late 2022, has left scientists puzzled, prompting a deep dive into the underlying causes. The Hektoria Glacier saw its front recede by approximately 8km (5 miles), a phenomenon that a recent study suggests could be the first observed instance of a grounded glacier rapidly destabilizing.
Researchers propose that Hektoria might represent a new type of glacial behavior where the glacier’s front, resting on the seabed, becomes unstable. This process, if widespread, could significantly accelerate sea-level rise globally. However, this interpretation is not universally accepted, with some scientists arguing that the glacier’s front was already floating, making the observed changes dramatic but not entirely unprecedented.
Solving the ‘Whodunnit’
The extent of Hektoria Glacier’s change is undisputed, with satellite data revealing a retreat of about 25km (16 miles) between January 2022 and March 2023. The study’s lead author, Naomi Ochwat, described the investigation into the causes as a “whodunnit” mystery.
The glacier’s unusual behavior is linked to the collapse of the Larsen B ice shelf in 2002, which had been acting as a natural barrier. Its absence accelerated Hektoria’s movement and caused thinning. While the bay was later filled with sea ice anchored to the seabed, partly stabilizing Hektoria, this ice broke up in early 2022.
The study suggests that the glacier’s retreat was amplified by an ‘ice plain’—a flat seabed area where the glacier lightly rested. Ocean water could have lifted this thinning ice, causing rapid iceberg calving and accelerating the retreat. Co-author Adrian Luckman highlighted the significance of this potential mechanism, stating, “Glaciers don’t usually retreat this fast,” and suggesting it could be a precursor to similar events in other parts of Antarctica.
This process, if confirmed, is particularly significant as it has not been observed in modern times, though seafloor evidence suggests it may have occurred in Earth’s past. The implications for sea-level rise are considerable, potentially affecting areas like the Thwaites Glacier, often dubbed the “doomsday” glacier due to its vast ice volume.
Other Scientists Unconvinced
Despite the compelling findings, some researchers express skepticism regarding the study’s conclusions. The primary point of contention lies in pinpointing the exact location of Hektoria Glacier’s grounding line—the boundary where the ice transitions from resting on the seabed to floating. Glaciologist Frazer Christie noted the difficulty in obtaining accurate satellite radar data in this dynamic region, leading to significant debate within the scientific community.
Christine Batchelor, a senior lecturer in physical geography, explained that if the glacier section was indeed floating, the event would be classified as iceberg calving from an ice shelf, a more common occurrence. She added, “I think the mechanism and rate of retreat proposed are plausible in Antarctic ice plain settings, but because of uncertainty about where the grounding zone was located at Hektoria, I am not fully convinced that this has been observed here.”
Regardless of the precise mechanism at Hektoria, there is widespread agreement that Antarctica is undergoing rapid changes, exceeding previous expectations. Anna Hogg, a professor of Earth observation, emphasized the need for more satellite data to better monitor and understand these accelerating changes and their impact on global sea levels.