Antarctic Ice Cores Offer a Whiff of Earth’s Ancient Atmosphere

[Elderberry]

Earth & Space Science News By Katherine Kornei 27 November 2019

Bubbles of greenhouse gases trapped in ice shed new light on an important climate transition that occurred about a million years ago.

To determine how Earth’s climate has varied over time, scientists are constantly on the lookout for the oldest whiffs of our planet’s atmosphere. The current record holders, recently extracted from Antarctic ice cores and dated to over 2 million years old, reveal concentrations of gases like carbon dioxide (CO2) and methane in ancient Earth’s atmosphere.

Researchers have now shown that levels of these greenhouse gases fluctuated less millions of years ago than they did in more recent times. That discovery has implications for how Earth transitioned between two climatic periods roughly a million years ago, the team reported.

Two Worlds

The climatic history of Earth has been far from constant: For the past 800,000 years, continental-scale ice sheets have repeatedly grown and retreated in glacial-interglacial cycles occurring roughly every 100,000 years (the “100K world”). (The current interglacial period, which has persisted for about the past 11,000 years, is known as the Holocene.)

But records stretching back further in time—to between 2.8 million and 1.2 million years ago—suggest that glacial-interglacial cycles were shorter and lasted only about 40,000 years (the “40K world”). However, there have been no direct observations of atmospheric greenhouse gases from that long ago. Until now.

More: https://eos.org/articles/antarctic-ice-cores-offer-a-whiff-of-earths-ancient-atmosphere