Antarctic Ice Cores Offer a Whiff of Earth’s Ancient Atmosphere
https://eos.org/articles/antarctic-ice-cores-offer-a-whiff-of-earths-ancient-atmosphere
Source: By Katherine Kornei. Eos/AGU.
Excerpt: 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. ...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. Yuzhen Yan, a geoscientist at Princeton University when this research was conducted, and his collaborators spent 7 weeks in Antarctica during the 2015–2016 austral summer collecting ice cores. ...Yan and his colleagues drilled into “blue ice,” a rare type of ice that’s been compressed over time. Scientists value it because it’s often very old, even when relatively near the surface. In the Allan Hills, blue ice is being pushed toward a mountain and is slowly uplifting, Yan said. “What used to be buried very deep…is progressively getting closer to the surface.” At the same time, strong winds ablate the ice from the top, progressively removing younger material....
Source: By Katherine Kornei. Eos/AGU.
Excerpt: 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. ...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. Yuzhen Yan, a geoscientist at Princeton University when this research was conducted, and his collaborators spent 7 weeks in Antarctica during the 2015–2016 austral summer collecting ice cores. ...Yan and his colleagues drilled into “blue ice,” a rare type of ice that’s been compressed over time. Scientists value it because it’s often very old, even when relatively near the surface. In the Allan Hills, blue ice is being pushed toward a mountain and is slowly uplifting, Yan said. “What used to be buried very deep…is progressively getting closer to the surface.” At the same time, strong winds ablate the ice from the top, progressively removing younger material....