Highlights
- Antarctic ice core evidence suggests the Ross Ice Shelf and West Antarctic Ice Sheet were far smaller during the Last Interglacial warm period about 129,000–116,000 years ago.
- Scientists identified volcanic dust from nearby Antarctic ice-free regions replacing South American dust, signaling major environmental and wind-pattern changes linked to ice sheet retreat.
- Larger, coarse dust particles preserved in the ice point to a local Antarctic source and a more open Ross Sea during warmer conditions.
- Climate simulations support the findings, raising concerns about future West Antarctic Ice Sheet stability and its potential to contribute 3–5 meters of global sea-level rise.
Antarctica’s Ross Ice Shelf and the West Antarctic Ice Sheet may have been far smaller during one of Earth’s most recent warm periods, according to a new study that traced the origin of ancient dust preserved in Antarctic ice. Previous modeling studies suggest that the melting of the West Antarctic Ice Sheet could raise global sea levels by between three and five meters.
The research team found that dust from volcanic and ice-free regions around the Ross Sea replaced dust originating from South America, the dominant source during colder periods. This shift in origin they say reflects significant changes in the Ross Sea environment and regional wind patterns caused by a major retreat of the West Antarctic Ice Sheet.
Published in Nature Geoscience, the study analyzed dust trapped in a coastal Antarctic ice core that captures the Last Interglacial (warm) period, approximately 129,000 to 116,000 years ago. Dust particles carry chemical signatures that reveal their origins, which allows researchers to trace how dust sources around the Ross Sea changed as the climate warmed.
“We found a volcanic signature rarely seen before in Antarctic ice from a warm period, and it was really perplexing at first,” said coauthor Sarah Aarons, a geochemist at the Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School. “Seeing volcanic rock material in the dust record suggested that parts of the Ross Sea region may have been exposed during that warm period,” said Aarons, who is also an assistant professor in Columbia’s Department of Earth and Environmental Sciences.
Reading the Dust
The study used an ice core drilled at the Allan Hills Blue Ice Area in East Antarctica. The site lies close to the margin of the East Antarctic Ice Sheet and within about 60 miles (100 km) of the Ross Sea, making it especially sensitive to environmental changes along the Antarctic coast.
Blue ice areas expose very old Antarctic ice unusually close to the surface through a combination of ice flow and surface weathering. This exposure allowed the scientists to have relatively easy access to ice that recorded both the cold glacial conditions that preceded the Last Interglacial as well as the transition into it.
The study team measured the concentration, size and chemical composition of mineral dust preserved in the ice core. Throughout the colder glacial period preceding the Last Interglacial, the dust had a chemical signature consistent with southern South America, a well-established source of Antarctic dust in glacial climates.
During the warmer interglacial period, the ice began to record young volcanic rock material from ice-free regions near McMurdo Sound in the West Antarctic Rift System. Antarctic ice from warm periods typically contains much less dust than glacial ice, making the detection of a volcanic signal notable. The absence of distinct volcanic layers in the ice core supports the interpretation that the material originated from exposed Antarctic terrain rather than isolated volcanic eruptions.
The characteristics of the dust particles also changed. Researchers found larger, more angular grains during the warm interval, including coarse particles that are difficult for wind to transport over long distances. That finding strengthened the case for a nearby Antarctic origin.
“The bigger the particle, the faster it will fall out of the atmosphere,” said lead author Austin Carter, a postdoctoral research associate at Princeton University. “Ice from the Last Interglacial contained more of these coarse particles, which points to a dust source much closer to Antarctica rather than material transported across the Southern Ocean.”
Reconstructing a Different Ross Sea
To understand what might have driven the shift in dust sources, the researchers combined the ice core data with climate model simulations. They tested three different Ross Sea ice sheet scenarios—preindustrial, partially collapsed and fully collapsed—to see if they could reproduce the dust record.
“Our simulations show that the loss of Ross Ice Shelf ice results in increased dust flux, snow accumulation, and wind speed along the Ross Sea coastline toward the Allan Hills ice core site,” Carter said. “This supports the idea of an open Ross Sea and even a diminished West Antarctic Ice Sheet during the Last Interglacial.”
The floating Ross Ice Shelf acts as a barrier that slows the movement of ice from the West Antarctic Ice Sheet into the ocean. Much of this ice sheet rests on bedrock below sea level, making it especially vulnerable to retreat if the Ross Ice Shelf weakens or disappears.
A Window Into a Warmer Antarctica
The Last Interglacial is one of the clearest natural examples scientists have of a world only marginally warmer than today. Temperatures at that time were between 0.5 and 1.5 degrees Celsius above preindustrial levels, yet sea levels are estimated to have been significantly higher than they are now.
For researchers studying Antarctic ice, the period offers an important comparison for understanding how ice sheets respond to relatively modest warming.
“If we know that during the Last Interglacial we probably had little or no Ross Ice Shelf and a diminished West Antarctic Ice Sheet, it may not bode well for future West Antarctic ice sheet stability,” Aarons said.
