By Kristy Hamilton
European scientists from 10 countries have spent years scouring the Antarctic ice sheet with one ambition in mind: to drill for the oldest-ever ice core. Now, they have zeroed in on just the spot.
The team have chosen Little Dome C – one of the coldest, most barren places on Earth. For the next five years, they will drill for a 1.5-million-year-old ice core – a frozen timepiece of Earth’s climatic past. The news was announced at the annual conference of the European Geosciences Union (EGU) in Vienna.
Their mission, called “Beyond EPICA-Oldest Ice”, will take place 30 kilometers (18.5 miles) away from the Concordia Research Station in what is a two-hour snowmobile ride to work.
The team finalized their location using radar and test drillings at depths of up to 400 meters (1,300 feet). Three criteria had to be met before they could gear up for a chilly five years: the ice is at least 1.5 million years old, there is a high chance of good resolution for scientific research, and the layers are undisturbed.
The current record for oldest ice core is 800,000 years old, taken by the European Project for Ice Coring (EPICA) project, an analysis of which revealed CO2 concentrations in the atmosphere over hundreds of thousands of years. These cores are records of ice that have built up over millennia – long icicle scrolls of sorts that have preserved knowledge of Earth’s ancient atmosphere.
The EPICA ice core provided scientists with plenty of information, but it also presented them with a mystery. They found that starting around 900,000 years ago, the climate changed from 40,000-year cycles to 100,000-year cycles. Researchers in the field don’t know why.
“This time interval is characterized by ice ages that were interrupted by relatively short warm periods, like the one that we are currently experiencing, every 100,000 years or so,” said Swiss team lead Hubertus Fischer, from the Oeschger Center at the University of Bern, in a statement. “The CO2 concentrations also changed at the same time: low values in ice ages, high values in warm periods.”
The team suspect the reason has to do with greenhouse gases, but until they gather more evidence, they can’t say for certain. That’s where the Beyond EPICA-Oldest Ice mission enters the investigation.
“After having analyzed the 800,000-year-old samples taken from the EPICA ice cores, we believe that there is good reason to drill into ice that is at least 1.5 million years old in order to get more information,” said mission coordinator Olaf Eisen from the Alfred Wegener Institute (AWI) in Bremerhaven..
“We know that our climate is changing,” added Eisen. “What we don’t yet fully understand is how the future climate will respond to increasing greenhouse gases in our atmosphere beyond 2100 and whether there will be tipping points in the system we are not aware of yet. It will be hugely helpful if we can understand what happens when the duration of natural climate cycles shifts. We can only get this information from the Antarctic ice sheet. To be able to embark on this mission is tremendously exciting.”
The team will analyze the gas bubbles in the ice to determine how the concentration of CO2 and methane has changed over time. It may sound counterintuitive but the fact that Little Dome C is dry and experiences little precipitation is actually good in this situation. The less snow that accumulates each year, the more years you can pack into each meter of ice.
“Ice is a very good insulator,” said Eisen to IFLScience. “An ice sheet is always heated from below by the geothermal heat flux. The thicker the ice, the more heat is stored at the base until the ice starts to melt. That means: too thick ice will cause melting at the base. At Little Dome C, this critical point is reached at a thickness of around 2800 to 2900 meters. At our proposed site the ice thickness is thinner, thus we don’t have melting.”
The most intriguing bit of the core will be the deepest layers – the meters when the bewildering transition took place. Such depths of around 2,730 meters (9,000 feet) won’t be reached until 2024, with the results released around 2025 if all goes to plan.
This article appeared on the IFLScience! website at https://www.iflscience.com/environment/scientists-drill-for-oldest-ice-on-earth-to-unlock-mystery-of-ancient-earths-changing-climate/