New method unlocks climate change secrets from the Tibetan ice

The researchers behind the new method, from the Institute of Tibetan Plateau Research in China, say their work will enable scientists to spot the molecules produced by burning forests more easily. This will help them understand the history of fires in the region, adding to the picture of how humans are contributing to climate change.

The Tibetan Plateau is one of the cleanest regions in the world. It is a huge area, covering around 1000km north to south and 2500km west to east, in western China and India. The glaciers supply water to people in surrounding countries and are critical for people's survival. However, they're retreating at an alarming rate, putting the water supply in jeopardy for more than 1 billion people.

Climbing temperatures are contributing to the disappearance of the glaciers. But previous research has also pointed to molecules in the air called carbonaceous aerosols as another cause of the glaciers melting. Carbonaceous aerosols are commonly produced by burning fossil fuels. However, almost half of the carbonaceous aerosols in south Asia are produced when people burn biomass, such as trees.

Studying the aerosols trapped in the ice of the glaciers can give scientists insights into the history of biomass burning and how it is related to climate change and glacial melting. For the new study, the researchers developed a method to help scientists identify a molecule called levoglucosan, which can identify carbonaceous aerosols that came from biomass burning.

Researchers often look for levoglucosan in snow and ice in Antarctica and the Arctic. However, ice from the Tibetan Plateau contains many more complex molecules, such as sugar and sugar alcohol, making it much harder to spot the levoglucosan.

"Carbonaceous aerosols can tell the story of biomass burning in a region, helping us understand more about how human activity has shaped glaciers over time," explained Mr. Chao You, lead author of the study from the Institute of Tibetan Plateau Research. "But it's quite difficult to identify the molecules that tell us when these aerosols were released, so we wanted to come up with a better method to use in Tibet."

Usually, researchers use a technique called High Performance Liquid Chromatography (HPLC) to identify levoglucosan in snow and ice samples. However, because of the insoluble particles in the Tibetan ice, using this method without pre-treating the samples can actually harm the system. Furthermore, levoglucosan is present at such low concentrations in the Tibetan ice that standard methods often can't identify the molecules.

Mr. You and his colleagues developed a method that can detect levoglucosan at tiny concentrations in snow and ice samples. The researchers first melted the ice, filtered it and mixed it with acetonitrile. They then analyzed the mixture using chemistry analysis called ultra-performance liquid chromatography combined with triple tandem quadrupole mass spectrometry. They then analyzed the levoglucosan in the sample.

The method is very sensitive: the team could identify levoglucosan at a concentration of only 110 nanograms per liter of ice. They could use the method with small samples of only 0.5ml. Also, the method is not just suitable for Tibetan ice, but for samples from any low and middle latitude glaciers around the world.

"I am interested in finding more evidence of biomass burning in Tibetan glacier snow and ice. To do this, we improved and tested this new method for identifying levoglucosan quickly and accurately in Tibetan ice and snow," explained Mr. You. "Our method can reveal more detailed information about the environmental process and changes that happened in Tibetan glaciers."

This research was supported by the National Scientific Foundation of China.