Key points
- The Southern Ocean plays an important role in absorbing carbon dioxide from the atmosphere.
- We’ve been collecting air from Antarctica with our research partners for the past 30 years.
- These air samples reveal how efficiently the Southern Ocean is absorbing carbon dioxide from the atmosphere.
Did you know that air samples taken from Antarctica can tell us about the health of our planet?
This winter, we asked our Bureau of Meteorology (Bureau) colleagues based at the Casey and Mawson stations in Antarctica to collect some air samples for us. In fact, they’ve been doing this every year since 1990. The samples provide us with a continuous set of observations. They are used by the international science community to build a full picture of our atmosphere and how it’s changing.
Bureau Technical Officer Clare Ainsworth was based at Casey Station, also home to a small wooden hut called Mabel. Inside Mabel is a special laboratory. This is where Clare completed the careful task of filling glass flasks with air.
"It's a privilege to be part of this program, knowing the data CSIRO collects is critical to understanding the impact of humans on the planet," Clare says.
"To be stationed here for a year is a long time away, especially from the children in my life – but the separation is a little easier knowing that I'm contributing to a big picture that we need to understand if we are to give them a sustainable future."
The samples collected at Mabel, like those at Macquarie Island and Mawson stations, are stored in special hard cases. These are then shipped once a year back to our GASLAB in Victoria. On home soil we analyse the samples for trace gases, including carbon dioxide, methane, nitrous oxide, hydrogen, and sulfur hexafluoride.
Ahead of each Antarctic season, we send back new empty flasks to our Bureau colleagues. And our scientific collaboration goes on.
Monitoring shifts in our atmosphere
The air samples collected in Antarctica form an important part of our monitoring network. This includes samples taken at Kennaook/Cape Grim in the northwest part of Tasmania. We’ve been jointly collecting air flasks at Cape Grim since 1978. However, the air flask work at Casey Station only started in 1996.
Dr Ann Stavert, our Senior Research Scientist, says Casey Station was chosen for its remote location.
"Cape Grim is generally considered to have some of the cleanest air in the world. But we sometimes encounter air there that has passed over Melbourne, rural Tasmania or Victoria," Ann says.
For example, during the 2019/20 Black Summer bushfires, scientists at our Kennaook/Cape Grim Baseline Air Pollution Station repeatedly observed smoke plumes passing over the station. These caused large spikes in some of the data.
While the flask collection can be timed to avoid pollution spikes, it is a reminder that even the isolated tip of north-east Tasmania isn’t immune to data variances or outliers.
Learning about Earth’s atmosphere from Antarctic air samples
Located on the Antarctic continent, the air collected at Casey is taken from the edge of the Southern Ocean far from land sources.
"These samples are particularly useful in trying to understand large scale changes in human-induced and natural greenhouse gas ‘sources’ and ‘sinks’ – especially in the Southern Ocean," Ann says.
Combined with air flask samples taken from other sampling stations like Cape Grim and Cape Ferguson (in northern Queensland) they give us a map of how gases change in our region. They also form part of a global baseline monitoring network that shows the average change of global greenhouse gas concentrations.
“We need measurements from multiple stations to get the big picture of what’s happening to the Earth’s climate,” Ann says.
Identifying the source of greenhouse gas emissions
More than 30 years of data from direct atmospheric sampling at Mawson and Casey can be merged with records from air retrieved from Antarctic firn (compacted snow) and ice to reconstruct the air histories over the last few millennia. The samples taken here help tell the story of how our atmosphere has changed in that time.
"It shows that even in the most pristine of environments the concentration of greenhouse gases is increasing," Ann says.
Aside from measuring direct and indirect greenhouse gases Ann and her colleagues at the GASLAB also measure the stable isotopes of carbon dioxide. Doing so helps them understand what the sources of human-caused carbon dioxide emissions are in the atmosphere.
"The stable isotope signal tells us the increase in carbon dioxide is driven by fossil fuel – human driven – sources," Ann says.
Understanding the Southern Ocean carbon sink
The Southern Ocean is one of the world’s most important sinks, taking up around 10 per cent of all the carbon dioxide emitted by humans. But there are significant doubts whether the rate it absorbs carbon dioxide will keep pace with a warming world. Warmer water is less effective at dissolving gases (like carbon dioxide) than cooler water.
The samples collected at Casey are helping scientists understand the strength of the Southern Ocean sink and how it might be changing.
"Monitoring dissolved carbon in the rough and icy waters of the Southern Ocean is challenging," Ann says.
One way of measuring dissolved carbon is through water samples collected on research voyages. These voyages usually take place during summer in the Southern Hemisphere. This is because of the extensive sea ice cover and extreme waves and weather events in the winter months. That means that ship-based observations of dissolved carbon have a ‘seasonal bias’ in the data.
"In contrast, we can measure air that has travelled from over the ocean throughout the year. Air samples allow us to track whether the Southern Ocean is absorbing as much carbon as models predict it should be," Ann says.
"The composition of the air samples can tell us about magnitude, seasonality and spatial differences in the interchange of carbon dioxide between the air and ocean."
Datasets informing global climate research
Flask measurements are made publicly available on the World Data Centre for Greenhouse Gases (WDCGG). Many groups have used these datasets over recent decades.
The data has been referenced in studies of all sizes from large international collaborations including the Global Carbon Budgets to national documents, like the State of the Climate 2022 report co-authored by us and the Bureau, used to inform Australian policy makers and government decisions makers. It has informed journal papers, including Strong Southern Ocean carbon uptake evident in airborne observations, published in Science.
We're working towards making the continuous measurements publicly available.