A team of scientists from Australia and the US are heading to Antarctica to research how the atmosphere’s ability to cleanse itself of greenhouse gases and other nasty chemicals has changed since the Industrial Revolution. They hope to discover more about the ‘natural air purifiers’ known to be present in the atmosphere using clues hidden deep in polar ice. The first researchers will arrive at the location in East Antarctica this week, after traversing more than a hundred kilometres to reach the remote site.
The temporary lab will be located at the Law Dome, a huge Polar ice cap that is 1,200 metres long and dates back to around 90,000 years. The high rate of snowfall creates annual layers in the ice that can be used to date each layer and the polar ice is also an excellent source of “old air,” ― air that has been trapped by huge snowfalls and preserved for centuries.
The team, led by Dr David Etheridge and Dr Vas Petrenko from the University of Rochester in the US and the Commonwealth Scientific and Industrial Research Organisation (SCIRO) in Australia, are planning to drill through the polar ice to depths of nearly 250 metres. The cores will then be melted to extract the bubbles of air that were trapped as the ice froze. The scientists hope to measure pre-industrial atmospheric levels of hydroxyl
The hydroxyl radical is a highly reactive chemical ― referred to by chemists as ‘the great unknown’ ― composed of an oxygen atom bonded to a hydrogen atom. The mystery molecule breaks down approximately 40 gases in the atmosphere that contribute to climate change and depletion of the ozone layer, including methane and hydrofluorocarbons, although not carbon dioxide (CO2). Scientists still don’t know how much of these gases are removed by hydroxyl radicals.
Hydroxyls are formed naturally in the atmosphere through a reaction involving ultraviolet rays, ozone, and water vapour. However, the newly-formed molecules quickly react with other gases and are therefore extremely short-lived, lasting only around one second. So, instead of measuring hydroxyl levels, the team will measure the concentration of carbon monoxide containing the carbon-14 isotope. The carbon-14 isotope is an excellent proxy since it is produced at a known rate and almost completely removed by hydroxyl. But this won’t be an easy task since there are only minuscule amounts of carbon-14 in the atmosphere and the ice is also at risk of being contaminated by external sources of carbon-14 once it is melted.
Ancient air offers a historical record unique to the so-called polar ice cores. Therefore, extracted cores from the Antarctic ice sheets hold an abundance of information about past and present climates. Interestingly, polar ice records from the Law Dome recently revealed a link between snowfall in Antarctica and drought in Southwestern Australia.
The new data will help to determine whether current atmospheric models showing historical trends in hydroxyl levels are accurate ― the models suggest concentrations were relatively stable between1850 and the 1970s but began to rise due to the increase in atmospheric warming at that time. Knowing more about hydroxyls and other ‘atmospheric detergents’ will also be fundamental to predicting the levels of gases that will affect the climate and ozone layer in the future.