Scientists Used a 1.7-Mile-Long ‘Time Machine’ to See Into Earth’s Climate Past

• Ice cores are climate scientists’ best way of understand Earth’s climate in the recent geologic past, largely because of the air bubbles trapped within them.
• An international team of scientists recently recovered a 1.7-mile-long ice core with ice samples dating back 1.2 million years (and possibly) later—400,000 years older than previous samples recovered by the team.
• This sample is particularly intriguing because it provides more context for the mysterious Mid-Pleistocene Transition—a period in Earth’s history when the glacial-interglacial cycle slowly changed from 41,000 years per cycle to 100,000 years.

Understanding Earth’s recent climate history—not just centuries, but millions of years in the past—requires some scientific creativity. Short of a flux capacitor-powered DeLorean ferrying climate scientists back to the early Quaternary, there is no way to directly observe the machinations of the Earth’s past climate. That’s why scientists get pretty jazzed about ice cores.

Massive glaciers (and the ice of which they’re comprised) can hang around for many millions of years, And trapped within the freezing lattices of these ice cores are pockets of air, which provide brief snapshots of atmospheric conditions throughout time. Now, the Institute of Polar Sciences of the CNR (National Research Council of Italy)—with funding from the European Commission—has collected one of the most impressive ice core samples ever meticulously extracted from Antarctic ice.

©PNRA, IPEV

The core was by an international team of scientists collected as part of the Beyond EPICA (European Project for Ice Coring in Antarctica) Oldest-Ice project. It came from the area of the Antarctic Ice Sheet known as “Little Dome C,” and measures a staggering 2,800 meters (9,186 feet) in length—roughly six-and-half times taller than the Empire State Building. Of course, the core isn’t in one continuous piece, but is cut into one-meter (3.2 feet) chunks.

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However, its most impressive accolade is that it contains ice at least 1.2 million years old, which is 400,000 years older than the previous EPICA ice core record. This ancient ice is particularly important because it was formed during a period known as the Mid-Pleistocene Transition, or MPT—a period of roughly 500,000 years when Earth’s glacial-interglacial cycle changed from a 41,000-year cycle to a 100,000-year cycle. Ice ages also became more intense after this transition.

“It was exciting to see the ice age as we drilled deeper, and especially when we knew we were drilling ice older than the EPICA record, which ended at 800,000 years ago,” Robert Mulvaney, a glaciologist and palaeoclimatologist at the British Antarctic Survey who worked on previous drilling seasons, said in a press statement. “This record of 1.2 million-years will give us several 41,000-year glacial cycles to compare with the more recent data from the original EPICA core.”

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Getting this record-breaking ice core wasn’t easy. Scientists had to first find the perfect spot, where the ice both contained a usable climate record and wasn’t so thick that the oldest ice layers had melted (this can happen if heat escaping the Earth’s mantle is trapped by the ice sheet). After using radio echo sounding technology to determine the perfect location, crews then had to work across four summers at Little Dome C, which is located at 10,500 feet above sea level and where the average temperature hovered around -35 °C (-31 °F). Thankfully, the hard work and dedication paid off.