Scientists restore Earth’s “memory” with mountaintop ice

People are fascinated by the distant past of our planet. Since human recorded history goes back only a few thousand years, we investigate the Earth’s “memory” in various ways to uncover its secrets. One of those methods is hunting for clues from the past, also known as “proxies,” which help scientists understand what Earth was like long ago.

A recent study published in PNAS describes the planet’s history by extracting previously unavailable information from ice cores from the western Kunlun Mountains.

Ice cores are columns of ice that have been drilled through glaciers found in extreme environments such as the Arctic, Antarctica and the Third Pole, which is located in the center of the Tibetan Plateau.

Ice cores are amazing as they record everything in the atmosphere and freeze it in time. They are windows that unlock mysteries of the past as they record not only receptors for climate events, such as temperature and precipitation, but also record evidence of climate-influencing events, such as ash and sulfates from volcanic eruptions. the cosmic nuclei chlorine 36 and beryllium 10 indicating changes in energy production from the sun. and the chemistry of air trapped in ice bubbles that show the past composition of Earth’s atmosphere. Ice cores also give us histories of temperature changes as they are recorded by the chemistry of snow that falls on glaciers and is later compressed into ice.

According to the editors of the recent PNAS Since 1950, the ice’s heavy oxygen to light oxygen (oxygen isotope) ratios have been the highest in 12,000 years, indicating recent dramatic changes in the climate of this region, which is undergoing rapid population growth and agricultural development.

While drilling ice cores at high altitudes is very difficult, extracting information from them can be even more so. According to Lonnie Thompson, the study’s lead author and a professor at Ohio State University’s Byrd Polar and Climate Research Center and School of Earth Sciences, understanding the climate record from the Tertiary ice cores is less straightforward than from polar ice cores, as they form under lower air pressure and contain more microorganisms and layers of melt, which can complicate the interpretation of ice chemistry.

Co-author Jeffrey Severinghaus of the Scripps Institution of Oceanography and the University of California, San Diego was able to adapt a method—previously used almost exclusively in polar ice core dating—to the Tertiary ice cores by adding new corrections.

“The air isotopes trapped in the ice bubbles and the atmospheric history of the last 15,000 years have been confirmed by other representative records,” said Yao Tandong, co-author of the study and a professor at the Tibetan Plateau Research Institute. , Chinese Academy of Sciences.

The ice cores used in this study were drilled from Guliya Ice in 1992 and 2015 by an expedition team led by Profs. Yao and Thompson, co-chairs of Third Pole Environment, an international science program designed to better understand changes in the Third Pole environment and their impacts.