Scientists have found trace sediment in the deepest ice of the South Pole Basin, likely carried downhill by ice flow over a subglacial mountain range and deposited over an estimated 14–30 million years. The discovery reveals variations in basal heat and melting that could help locate the oldest continuous Antarctic ice—potentially extending climate records beyond the current ~800,000-year limit. The work improves understanding of subglacial processes and has implications for sea-level rise and coastal risk.
Unexpected Sediment Found Under Antarctic Ice Could Extend Climate Records by Millions of Years
Scientists have found trace sediment in the deepest ice of the South Pole Basin, likely carried downhill by ice flow over a subglacial mountain range and deposited over an estimated 14–30 million years. The discovery reveals variations in basal heat and melting that could help locate the oldest continuous Antarctic ice—potentially extending climate records beyond the current ~800,000-year limit. The work improves understanding of subglacial processes and has implications for sea-level rise and coastal risk.
12:59 PM, 11/10/2025Science
Unexpected sediment discovered in the South Pole Basin
Researchers building a long-term climate record from Antarctic ice layers have found trace amounts of sediment in the deepest ice of the South Pole Basin, the University of Texas Institute for Geophysics reported via Phys.org. The team says the grains were likely picked up as ice flowed down a subglacial mountain range and were deposited in the basin over millions of years.
"We were not expecting this," said Duncan Young, a research scientist at the University of Texas Institute for Geophysics. "We think that as the ice melted, the basal unit carried small amounts of material from the mountain range and left sediment behind."
Young and his colleagues estimate this process unfolded gradually over roughly 14–30 million years. The finding gives scientists new clues about basal conditions beneath the ice sheet—particularly how geothermal heat and subglacial topography influence melting and sediment transport.
Why this matters for climate research
Ice cores are time capsules: chemical signatures and tiny air bubbles trapped in successive layers record past climate. Because ice accumulates in chronological order—like tree rings—deeper layers represent older climates. Locating areas with the oldest continuous ice could extend our climate record beyond the current oldest sample, which dates to about 800,000 years.
Where bedrock and substrate contain more sediment, higher geothermal heat can produce basal melting and form subglacial lakes. Finding sediment in the South Pole Basin therefore helps researchers identify regions with distinct basal heat flow and melting histories—key information when searching for ancient, undisturbed ice.
Broader implications
Understanding subglacial heat and melting is also relevant to modern environmental concerns. Glacial melt contributes to rising sea levels, which threaten coastal communities by damaging property, lowering property values and increasing insurance costs. Saltwater intrusion from sea-level rise can also harm freshwater ecosystems.
The research team plans to continue mapping how basal heat flow and temperature vary beneath the Antarctic ice sheet. As Young explained, "understanding how the heat flow varies at the base of the ice sheet and what the temperature is there is critical for finding places where the oldest continuous ice might be preserved."