Scientists have taken a new look beneath one of East Antarctica’s most closely watched glaciers, finding that part of its bed may lie substantially higher than previous maps suggested.
Denman Glacier has attracted particular attention because models have placed it above an extraordinarily deep trough, with estimates suggesting the bed could reach between 2.6 and 3.5 kilometres below sea level. The glacier also contains enough ice to raise global sea level by more than 1.5 metres if it were to melt completely.
But new measurements from the Denman Terrestrial Campaign challenge the existing picture.
Researchers deployed geophysical instruments directly on the glacier, including equipment using a technique known as magnetotellurics. By measuring natural variations in the Earth’s electric and magnetic fields, the technique can help distinguish ice from the rock, sediment and water beneath it.
The results suggest that, along the central section surveyed, the bed is about 1,600 metres below sea level, with an uncertainty of around 200 metres. That is more than a kilometre shallower than estimates from widely used models. The measurements were made along a transect about 50 kilometres upstream of Denman’s grounding line.
A shallower bed could indicate the presence of a previously poorly resolved topographic high beneath the glacier. Such a feature might potentially provide a natural obstacle to retreat. But the researchers also detected electrically conductive areas beneath the ice, interpreted as water-rich sediments or material. These conditions could reduce friction and make it easier for the glacier to slide.
The finding therefore does not settle the question of Denman’s future. Researchers were able to measure only parts of the trough, and further observations will be needed to establish its wider shape. Instead, the study demonstrates how much remains hidden beneath the Antarctic ice, and why better observations of that landscape matter for projections of future ice loss and sea-level rise.