A 3.7km deep ice core containing 400,000 years of trapped air bubbles. Proving that CO₂ and temperature have moved in lockstep throughout history.
Todd Sowers, LDEO, Columbia University, Palisades, New York, Public domain
Earth's Oldest Atmosphere
At Russia's Vostok Station, the coldest inhabited place on Earth, scientists have drilled deep into the Antarctic ice sheet. On July 21, 1983, the station recorded the lowest natural temperature ever measured on the planet's surface: -89.2°C (-128.6°F). This remote outpost sits on more than 3,700 meters of ice. Beginning in the 1970s, a decades-long drilling project extracted a cylinder of ice—an ice core—that contains a detailed record of Earth's climate stretching back 420,000 years.
The Vostok core is an archive of past environmental conditions. Each layer of ice represents a year's snowfall, and trapped within these layers are tiny bubbles of ancient air. By analyzing the gas in these bubbles, researchers can directly measure the composition of the atmosphere from distant epochs. The ice itself holds clues to past temperatures, preserved in the ratios of hydrogen and oxygen isotopes.
The data from this core shows an unambiguous correlation between atmospheric carbon dioxide concentrations and global temperatures over four complete glacial cycles. During ice ages, CO₂ levels dropped to as low as 180 parts per million. In the warmer interglacial periods, they rose to around 280 ppm. The temperature and CO₂ levels track each other with remarkable consistency through millennia of climate shifts.
A Lake Beneath the Ice
The drilling project at Vostok led to an entirely separate discovery. In the 1970s, airborne radar surveys detected strange readings beneath the station. By 1993, using satellite data, scientists confirmed the existence of a vast subglacial body of water named Lake Vostok. It is one of the largest lakes in the world, with a surface area of 12,500 square kilometers and a volume of 5,400 cubic kilometers.
The lake exists in liquid form despite the extreme surface cold because it is insulated by nearly 4 kilometers of overlying ice and warmed by geothermal heat from the Earth below. Its water has been isolated from the surface for an estimated 15 million years. Drilling was halted in 1998 at a depth of 3,623 meters to avoid contaminating this unique environment. A mixture of kerosene and Freon was used as a drilling fluid to keep the borehole from freezing shut under immense pressure. In 2012, after developing special protocols, a Russian team finally pierced the ice sheet and reached the lake's surface. Analysis of refrozen lake water from the bottom of the ice core has revealed a diverse ecosystem of microbes, including bacteria, fungi, and archaea, that have evolved in this dark, cold environment.
💡Fun Facts
The lowest temperature ever recorded, -89.2°C, is so cold that humans can only inhale the air for a few breaths without causing lung damage.
Lake Vostok is similar in surface area to Lake Ontario but holds a larger volume of water due to its greater depth.
The drilling project that produced the main ice core began in 1990 and took years to reach its final depths, with the hole having to be re-drilled multiple times due to drills getting stuck.
The ice at the very bottom of the core is refrozen from the lake itself and does not contain climate data, but does contain evidence of microbial life.
