Oldest Ice Core Dates Back 1.5 Million Years, Revealing Earth's Climate

How old is the oldest ice core? Good question. These cores can provide valuable information about Earth's climate and greenhouse gases. Now, scientists have found the location of what they believe is the oldest ice core--one that dates as far back as 1.5 million years.

Ice cores are often used by climate scientists. They allow researchers to better understand how temperature responds to greenhouse-gas concentrations in the atmosphere. This, in turn, allows them to make better predictions about how climate will shift in the future--something that's doubly important considering the current rate of climate change.

Scientists have found old ice cores in the past. In fact, a 3.2-km-long core was drilled almost a decade ago at Dome Concordia in Antarctica. This particular core dated back 800,000 years. Yet scientists wanted to know what exactly happened before that.

"The Mid Pleistocene Transition is a most important and enigmatic time interval in the more recent climate history of our planet," said Hubertus Fischer, one of the researchers, in a news release.

In order to find out about this period, they needed to find an ice core that dated back that far. As snow falls and settles on the surface of an ice sheet, it is compacted by the weight of new snow falling on top of it and is transformed into solid glacier ice over thousands of years. The weight of the upper layers compresses the lower ones, causing them to become thinner with depth. This produces very old ice at depths close to the bedrock.  Yet if ice thickness is too high, then the old ice at the bottom becomes warm via geothermal heating and melts away.

"To constrain the possible locations where such 1.5 million-year-old-and in terms of its layering undisturbed-ice could be found in Antarctica, we compiled the available data on climate and ice conditions in the Antarctic and used a simple ice and heat flow model to locate larger areas where such old ice may exist," said Erick Wolff, co-author of the new study, in a news release.

In the end, the researchers found that it's very likely that 1.5 million-year old ice should exist at the bottom of the East Antarctica in regions close to the major Domes. These Domes are the highest points on the ice sheet. In addition, this old ice should also exist near the South Pole.

Currently, the researchers plan to survey the identified drill sites to measure the ice thickness and temperature at the bottom of the ice sheet. This will allow them to identify the most suitable and final drill location.

"A deep drilling project in Antarctica could commence within the next three to five years," said Fischer in a news release. "This time would also be needed to plan the drilling logistically and create the funding for such an exciting large-scale international research project, which would cost around 50 million euros."

The findings are published in the journal Climate of the Past.