A core drilled through the East Antarctic ice sheet
On 9 January 2025, the Beyond EPICA - Oldest Ice consortium announced that its fourth drilling campaign had reached bedrock at Little Dome C in East Antarctica. The recovered core is about 2,800 meters long. Preliminary measurements indicate that its upper 2,480 meters preserve a continuous climate record extending to roughly 1.2 million years ago, about 400,000 years beyond the celebrated EPICA Dome C record completed two decades earlier.
The site lies about 35 kilometers from the Italian-French Concordia Station, at an elevation near 3,200 meters. Sixteen researchers and support staff worked in average summer temperatures around minus 35 degrees Celsius during the final field season. Across four campaigns, drilling and core processing required more than 200 working days. Reaching bedrock is therefore both a scientific milestone and a demanding logistical result.
It is also the start of the main analysis, not its conclusion. At the time of the announcement, researchers had recovered the archive and made preliminary age assessments. Detailed measurements of its gases, isotopes, dust and chemistry were still to come.
Why ancient ice records more than temperature
Snow accumulating on the Antarctic plateau is compressed into ice. Variations in the ratios of stable water isotopes provide evidence about past temperatures and moisture sources. Dust, sea salts, volcanic products and other impurities record changes in winds, aridity, ocean influence and eruptions. Most unusually, bubbles sealed between ice crystals preserve samples of the ancient atmosphere.
Those bubbles let laboratories measure carbon dioxide and methane directly rather than infer them only from biological or geological proxies. Researchers can then align greenhouse-gas concentrations with temperature indicators from the same core. Dating and synchronizing the layers remains difficult at great depth because annual snowfall is compressed into extremely thin sections; the team estimates that as many as 13,000 years may be packed into one meter of the oldest useful ice.
The cores had to travel to Europe aboard the icebreaker Laura Bassi while remaining below minus 50 degrees Celsius. Specialized containers and a coordinated air, overland and sea route protected the physical sequence and the trapped gases from warming damage.
A window on the Mid-Pleistocene Transition
The primary target is the Mid-Pleistocene Transition, approximately 900,000 to 1.2 million years ago. Before this interval, glacial cycles followed Earth's orbital variations with a dominant rhythm near 41,000 years. Afterwards, large ice-age cycles became longer and stronger, recurring roughly every 100,000 years even though orbital forcing did not acquire a matching new 100,000-year pulse.
Scientists have proposed changes in ice-sheet size, bed conditions, ocean circulation, atmospheric carbon dioxide and feedbacks among them. Existing continuous ice cores reach back about 800,000 years, so they begin after much of the transition. Beyond EPICA is designed to put direct greenhouse-gas measurements beside temperature and dust records across the change itself. The core cannot by itself prove one cause, but it can rule out explanations whose predicted timing or gas response conflicts with the sequence.
The deepest ice needs separate treatment
The consortium reports that the interval from about 800,000 to 1.2 million years ago appears where ice-flow models predicted, between roughly 2,426 and 2,490 meters depth. Below the continuous record, however, the lowest approximately 210 meters are heavily deformed and may contain mixed or refrozen ice of uncertain origin. Those samples could be even older, but they cannot automatically be read as an ordered timeline.
Researchers will analyse that basal material with methods suited to disturbed ice and date rock fragments from beneath the sheet. Those measurements may reveal when this part of East Antarctica was last ice-free. Until laboratory dating is complete, claims of ice older than 1.2 million years remain possibilities rather than established ages.
The secure 2025 achievement is the recovery of a uniquely long core from a site selected through radar surveys and ice-flow modelling. Its scientific payoff will arrive measurement by measurement, as laboratories reconstruct how greenhouse gases, temperature and the great ice sheets interacted across a transformation in Earth's climate system.
