Researchers discovered the most complete terrestrial climate archive of the past five million years in an 80-metre-thick sedimentary sequence in Charyn Canyon, Kazakhstan, conveying a detailed track record of the interactions between ocean, land, and atmosphere.
An international team of researchers led by the Max Planck Institute for Chemistry, in a laboratory in Mainz, Germany, has successfully reconstructed the changes in rainfall of the past five million years, providing a missing link for understanding the land–water feedbacks crucial for grasping the changes in global climate over time.
“The 80-metre-thick sedimentary sequence we found provided us with a virtually continuous record of five million years of climate change,” explains Charlotte Prud’homme, one of the Paleo researchers involved. The alternating layers of soil and dust are the first reliable evidence of long-term interactions between the Siberian high and the rain-bringing westerly airflows, the major climate systems on the Eurasian continent. Timewise, the research focused on the investigation of the Pliocene and Pleistocene periods (between five and 2.6 million years ago). With a carbon dioxide concentration of 400 parts per million (ppm) in the atmosphere, this period closely resembles the climatic conditions of the Anthropocene.
The researchers abseiled down into the canyon to retrieve samples from alternating layers of dust and soil. By determining the age and accumulation rates of the sediment record through measuring the relative concentration of isotopes within the soil carbonates, it was revealed that in the Pliocene the soil was significantly wetter than today. This indicates a non-linear process of aridification, which was occasionally interrupted by short-term climate fluctuations. Consequently, this provided valuable insight into the long-term interaction between the mid-latitude westerly winds and the Siberian high-pressure.
Kathryn Fitzsimmons, a researcher from the Terrestrial Paleoclimatic Research Group of the Max Planck Institute for Chemistry, explains that this could be used as a proxy for the Siberian rivers—e.g., Irtysh or Ob—further north, as they were influenced by the same climate conditions. There was one particular phase where this link stands out: About 3.3 million years ago, right before the first major global glaciation, there was a sustained period of wet conditions, which is quite likely to extend north.
So far, the Earth’s climate evolution has only been explored through marine mechanisms ignoring the significance of the climate feedback originating on land rather than from the ocean, lakes, or ice cores. The research conducted fills this gap allowing to base future climate models on the newly acquired knowledge.