The EPICA Dome C ice core transformed 3.2 kilometers of East Antarctic ice into a climate sequence spanning roughly 800,000 years. Its importance comes from more than reaching an impressive age. The core follows consecutive layers through eight glacial cycles, pairing evidence of Antarctic temperature with ancient greenhouse gases, dust, salts, and other chemical signals in one long archive.
For years, the Vostok core supplied the leading Antarctic record, extending through about 420,000 years. EPICA nearly doubled that reach. The added interval exposed a different style of glacial–interglacial behavior before about 430,000 years ago and gave researchers a much stronger basis for distinguishing persistent climate relationships from patterns visible in only a few cycles.
Drilling Toward Bedrock
EPICA, the European Project for Ice Coring in Antarctica, drilled at Dome C on the high East Antarctic Plateau. The site was selected because its thick, comparatively slow-moving ice offered a chance to recover a long and orderly sequence. Low snowfall also helped: fewer annual layers accumulated in a given thickness, allowing a drill to travel far back in time before reaching the bottom of the ice sheet.
The final borehole descended to approximately 3,270 meters, stopping only a few meters above bedrock. Reaching that depth was not equivalent to reading the record. Core sections had to be logged, transported without thawing, sampled by many laboratories, and aligned on a common chronology. Researchers measured the water’s isotope ratios, greenhouse gases released from bubbles, airborne dust, sea-derived ions, and volcanic products. Separate measurements acquired their meaning only after depth was converted into age.
The resulting timeline is not a stack of 800,000 individually counted annual layers. Near the surface, seasonal changes may be resolved clearly. Deeper down, pressure and ice flow compress old layers until thousands of years occupy a short length of core. Dating therefore combines accumulation and flow models with independently recognizable markers and comparisons among climate records. In modern Antarctic chronologies, the uncertainty near the oldest EPICA Dome C ice can reach several thousand years.
From 740,000 to 800,000 Years
The project’s first major long-record result, published before every analysis of the deepest ice was complete, extended the climate sequence to about 740,000 years. A high-resolution deuterium profile later carried the Antarctic temperature reconstruction to approximately 800,000 years, while gas measurements from the lowest sections extended the atmospheric carbon dioxide record across the same broad span.
That progression explains why both numbers appear in descriptions of EPICA. They do not identify rival cores or a simple correction of an error. They reflect stages in analyzing, dating, and interpreting the deepest material. “About 800,000 years” became the standard summary for the completed paleoclimate archive, not a claim that every variable is equally resolved at every depth.
The Extra Cycles Changed the Picture
The younger half of the EPICA sequence agrees closely with Vostok in its broad Antarctic climate pattern, strengthening confidence that the major swings were regional rather than peculiar to one drill site. The older section, between approximately 800,000 and 430,000 years ago, revealed interglacials that were generally less intensely warm in Antarctica. Yet the climate often occupied the warmer part of its range for a larger fraction of a cycle.
This contrast brackets the Mid-Brunhes Event, a shift around 430,000 years ago after which interglacials tended to become warmer. EPICA did not reduce that change to one simple trigger. Instead, it supplied the long record required to test how orbital geometry, greenhouse gases, ice sheets, ocean circulation, and feedbacks combined differently through time.
The core also showed that atmospheric carbon dioxide tracked Antarctic temperature across all eight cycles. The lowest measured glacial values in the oldest portion expanded the known natural range, while no interglacial in the record reproduced the modern concentration produced by industrial emissions. Dust measurements added another dimension: cold intervals were generally dustier, reflecting changes in continental dryness, winds, transport pathways, and the area of exposed shelves.
A Benchmark Surpassed but Not Replaced
EPICA Dome C no longer defines the oldest ice ever recovered. Ancient, discontinuous ice from blue-ice fields reaches much farther back, and the Beyond EPICA drilling effort at Little Dome C has extracted a core containing ice older than 1.2 million years. The newer core is intended to cross the Mid-Pleistocene Transition, when dominant glacial pacing changed from roughly 41,000-year cycles toward longer, stronger cycles near 100,000 years.
Recovering older ice does not make the original EPICA sequence obsolete. New records must be dated, checked for disturbed layers, and analyzed across laboratories before their climatic story is secure. EPICA Dome C remains the reference against which that work is compared: an unusually long, internally connected account of how temperature, atmospheric composition, and airborne material changed together over most of the late Pleistocene.