The Hektoria Glacier on the Antarctic Peninsula retreated by at least 8 kilometres in 2 months, a rate nearly 10 times faster than previously measured for a grounded glacier, according to a study published in Nature Geoscience and reported by the Australian Science Media Exchange.
This record-breaking retreat may be explained by a minimally studied glacier destabilisation process that could occur in similar settings, the authors suggest.
Grounded – or non-floating – glaciers in polar regions generally retreat no more than a few hundred metres per year. The retreat of glaciers, meanwhile, contributes to sea level rise as they melt. Therefore, understanding how quickly polar glaciers can retreat and what factors influence their retreat rate is important for accurately forecasting sea level rise with global warming.
Naomi Ochwat and colleagues observed that the February 2022 to August 2023 period coincided with a series of earthquakes recorded in the region, the waveforms of which were consistent with icebergs calving from a grounded glacier. They propose that the extreme retreat rate resulted from the glacier retreating onto an ice plain, a flat area of bedrock that the glacier rests on near where the glacier transitions from grounded to floating.
As the grounded glacier thinned, the whole ice plain region became exposed to buoyant forces from the ocean, which caused it to go afloat and promoted further calving. The authors note that ice plains have been identified elsewhere and argue that mapping the topography beneath glaciers around Greenland and Antarctica is important to evaluate the potential for similar sudden glacier destabilisations and their impact on sea level rise.