Scientists have achieved a breakthrough in Antarctic research, retrieving a record-breaking sediment core from beneath the West Antarctic Ice Sheet. The 228-meter core, extracted from a depth of 523 meters of ice at Crary Ice Rise, provides an unprecedented glimpse into the region’s climate history spanning the past 23 million years – including periods significantly warmer than today.
The international team, part of the Sensitivity of the West Antarctic Ice Sheet to 2 °C (SWAIS2C) project, believes the core holds crucial clues to understanding the stability of the West Antarctic Ice Sheet and its potential response to future warming. The sheet contains enough frozen water to raise global sea levels by four to five meters if it were to melt completely.
The drilling site, Crary Ice Rise, was strategically chosen for its location near the edge of the Ross Ice Shelf, where the ice sheet is currently pinned to bedrock but is vulnerable to lifting off. This location allows researchers to study the conditions under which the ice sheet retreated in the past and potentially predict future behavior.
Evidence of a Past Open Ocean
Perhaps the most surprising discovery within the core is evidence suggesting that the region was, at least partially, an open ocean in the past. Shell fragments and remains of marine organisms requiring sunlight were found within the sediment layers. This indicates periods where the ice sheet retreated significantly, allowing for marine life to flourish. While scientists previously suspected this was the case, the core provides direct evidence and a detailed timeline.
“Some of the sediment was typical of deposits that occur under an ice sheet like we have at Crary Ice Rise today,” explained co-chief scientist Molly Patterson of Binghamton University. “But we also found shell fragments and the remains of marine organisms that need light – material more typical of an open ocean, an ice shelf floating over ocean, or an ice-shelf margin with icebergs calving off.”
The discovery is significant because it helps refine models used to predict the ice sheet’s future behavior. Until now, these models have relied on geological records from locations further afield, which may not accurately reflect the specific conditions in West Antarctica. The new core provides a localized, high-resolution record of environmental changes.
Reconstructing Past Climates
The core’s layers represent a chronological record of environmental conditions, allowing scientists to reconstruct past temperatures, ocean currents, and ice sheet extent. Initial dating, based on fossilized algae, suggests the core spans 23 million years, including periods when Earth’s average surface temperature was higher than current projections for 2100 under existing climate policies. This provides a valuable analog for understanding how the ice sheet responded to warmer climates in the past.
Huw Horgan, a co-chief of the project from Victoria University of Wellington, noted that the samples include periods with global average temperatures exceeding two degrees Celsius above pre-industrial levels. Studying these periods will help determine the temperature threshold at which the West Antarctic Ice Sheet’s retreat becomes irreversible.
“Satellite observations over recent decades show the ice sheet is losing mass at an accelerating rate, but there is uncertainty around the temperature increase that could trigger rapid loss of ice,” the research team stated in a report released on .
Logistical Challenges and Future Analysis
The expedition, involving 29 researchers, drillers, engineers, and polar specialists, was a significant logistical undertaking. The drilling site is located over 700 kilometers from the nearest Antarctic station, requiring extensive planning and support. The core samples were transported over 1,100 kilometers across the Ross Ice Shelf to Scott Base before being shipped to New Zealand for further analysis.
The analysis will involve detailed examination of the sediment’s composition, including the types of marine organisms present, the presence of chemical markers indicating past temperatures, and the dating of different layers. This will provide a comprehensive picture of the West Antarctic Ice Sheet’s history and its sensitivity to climate change.
The SWAIS2C project aims to determine how far the West Antarctic Ice Sheet retreated during previous periods of global warming and whether a critical temperature threshold exists beyond which its retreat becomes unstoppable. The data from this record-breaking core will be instrumental in refining climate models and improving predictions of future sea level rise, offering critical information for policymakers and coastal communities worldwide.
