A team of researchers from multiple institutions in the United States has successfully extracted an ice core from Antarctica’s Ong Valley that contains samples of Earth’s atmosphere dating back up to 5 million years. The researchers explain why they chose to drill in the Ong Valley and what they hope to learn from their ice core study in their paper published in The Cryosphere.
Scientists have been drilling and extracting ice cores in Antarctica for many years, with the goal of studying the air bubbles trapped in the ice, some of which date back millions of years, to learn more about the Earth’s atmosphere at the time.Until now, the majority of such core samples have come from sites in eastern Antarctica, where the ice has been slowly deposited in clean layers over millions of years.
Instead, the researchers chose to drill in the Ong Valley, which is located in the Transantarctic Mountains, which, as the name implies, separate eastern and western Antarctica. Glaciers that slid down from the mountains deposited ice in the Ong valley. As the ice on top melted, rocks dragged down from the mountains formed a layer of rock that shielded the ice beneath it.
Previous research has suggested that the ice beneath could be as old as 5 million years. The ice in the Ong Valley is not only older than the ice in the east, but it is also thinner, which means getting a useful core does not require drilling as deep.
Over the summers of 2017 and 2018, the researchers drilled through the ice, gaining access to the protected ice beneath the rock and extracting a 9.5-meter-long core sample. According to preliminary testing of the isotopes found in the ice, the age of the ice ranges from 3 million to just over 5 million years.Because cosmic rays collided with the rocks above, isotopes such as neon, aluminium, and beryllium can be used for age testing. The researchers also discovered that the ice sheet beneath the rocks is actually two sheets, one on top of the other, implying that two glaciers ended up in the valley millions of years apart.