The ice sheets of these cores reveal past temperatures, and the gases trapped in bubbles expose the atmospheric composition of the past.
The oldest continuous ice core so far comes from Dome C in East Antarctica and dates back 800,000 years. Now, a collaborative study between the University of Washington and the University of Maine (USA) offers a tantalizing clue to go back even further after identifying a place where an intact one million-year-old ice core could be preserved. antiquity.
This ice, buried in incredibly frozen places, is often mistaken for badlands, but by extracting deep, hidden ice cores from these extreme latitudes, we can learn just about anything: from metalworkers defeated by the Black Death, to the rise and fall. of the Roman Empire; or even the oxygen supply of our planet.
The funny thing is that this newly discovered ice core in the frozen depths of the Allan Hills in Antarctica, does not resemble any of these frozen lessons of Earth history.
“There is a strong desire to delay the date of the oldest ice record, to better understand what drives natural climate changes,” says polar geologist Laura Kehrl of the University of Washington to the journal Geophysical Research Letters that publishes the work.
“Allan Hills has been an area of interest since the 1970s, when scientists began finding lunar and Martian meteorites that had hit Earth a long time ago. Now we are discovering their potential for older ice ,” Kehrl said.
The Allan Hills lie within a region called the Transantarctic Mountains (between Cape Adare and Coats Land) whose steep and uneven topography long led to the belief that it was too unstable to contain deep, ancient ice of this type.
At least that was until last year, when a separate study by researchers at Princeton University (USA) found an isolated 2.7-million-year-old chunk of ice under the Allan Hills.
Unfortunately, because that broken fragment was separated from the rest of your icy timeline, there is a limit to how much it can tell us about Earth’s environmental conditions. But the discovery nonetheless showed that Allan Hills could be fertile territory for continuous million-year-old ice columns.
To investigate, experts set up a remote camp in Allan Hills at 1,950 meters above sea level, and used snow machines to drag ice-penetrating radar over the frosty, bluish surface. Radar signals bounce off hidden ice sheets below the surface, revealing differences in ice chemistry and density.
Using this technique – and computer modeling to simulate glacier flow in the area – the scientists claim to have identified the likely location of where a million-year-old ice core may lie under the Allan Hills , about 5 kilometers away. away from where the 2.7-million-year-old chunk of ice was discovered.
Scientists have applied to the National Science Foundation for permission to drill in the proposed area, and if approved, we could stumble upon an unprecedented, continuous core of unmatched age and composition.
Reference: Laura Kehrl et al, Evaluating the Duration and Continuity of Potential Climate Records From the Allan Hills Blue Ice Area, East Antarctica, Geophysical Research Letters (2018). DOI: 10.1029 / 2018GL077511
Image credit: Laura Kehrl / University of Washington
