Researchers have studied air hydrate crystals in an ice core recovered from Greenland. According to the scientists, the ice samples are about 130,000 years old. They used a combination of scanning electron microscopy and energy-dispersive X-ray spectroscopy to visualize and identify the molecules contained in the air hydrate crystals and found argon.
Snow “traps” air from the atmosphere and then turns into ice. Over centuries or millennia, ice accumulates, increasing the pressure and lowering the temperature in the “frozen” air bubbles. Then the trapped atmospheric molecules turn into cellular crystals, preserving samples of ancient air for hundreds of thousands of years. These crystals, known as air hydrates, can show how Earth’s atmosphere and climate have changed.
An ice core from the Greenland ice sheet. Photo: Tsutomu Uchida
Scientists used to study only traces of oxygen and nitrogen. Now an international research team has developed a new approach to identify more elusive, previously unconfirmed components such as argon.
“Air bubbles in the ice core are the only known paleoecological archive of a real ancient atmosphere with a time axis toward depth,” Tsutomu Uchida, associate professor of engineering at Hokkaido University, told the study’s first author.
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