Scientist’s 30-year search for Southern Ocean climate secrets
AFTER more than 24 hours the ice breaker still hadn’t managed to break through the heavy sea ice and Chief Scientist Dr Steve Rintoul had secretly given up hope. All that would change in seconds though, leading to the senior scientist’s greatest but most disturbing discovery of his 30 year career.
It was January 2015 when Rintoul and his team aboard the RSV Aurora Australis achieved what no others had managed – reaching the front of the Totten Glacier. They found that warm water was flooding into the cavity beneath the floating ice, melting what was thought to be a stable area of East Antarctica. The sea level rise problem had just got worse.
Two years on, Rintoul will return to the Southern Ocean aboard CSIRO’s research vessel Investigator, this time further east towards the Mertz Glacier, on an expedition to piece together some of the remaining unknowns of the climate-critical region.
With a physics degree from Harvard, post-graduate qualifications from MIT and Woods Hole, a post-doctorate from Princeton, and decades of experience in Southern Ocean research, Rintoul is more than qualified to lead the voyage.
“Over time, we are realising just how crucial the oceans are for climate, especially the Southern Ocean,” says Rintoul, a team leader at CSIRO’s Centre for Southern Hemisphere Oceans Research. “And one of the most important things we now know, is that the Southern Ocean soaks up huge amounts of heat and carbon dioxide from the atmosphere.”
“It was only really thirty years ago that we started to realise the deep oceans were changing, before then scientists had thought they were pretty stable,” he says. “But in 1990 the World Ocean Circulation Experiment started, where more than thirty countries set out to measure the global ocean for the first time.”
Rintoul had just moved to Hobart to take up a position with CSIRO and at 30 years old, found himself leading the Southern Ocean component of the huge international experiment. It was this opportunity that would see CSIRO participate in its very first southern ocean research project and give Rintoul the reins for what would be his first of 13 Antarctic voyages.
Antarctica is a long way from Rintoul’s childhood home of Westport, a coastal town an hour’s drive from New York City. It was here his curiosity for the ocean would grow, sparked by his mother who was a science teacher.
“Up until the WOCE project, ocean measurements had been largely piecemeal and uncoordinated,” he says. “The ‘WOCE decade’ was a real turning point for oceanographic science because it gave us the first global snapshot of the oceans and a baseline for tracking future change.”
The project showed that the Southern Ocean did more heavy lifting with respect to global climate controls than any of the others, but because of its remoteness, conducting research provided a challenge.
“The 90s were really a golden era for Southern Ocean research, especially for Australia, which had up until then been mostly focussed on the continental shelf and coast,” he says.
“In 1991, funding became available through what is now called the Antarctic Climate & Ecosystems Cooperative Research Centre and combined with Australia’s new icebreaker Aurora Australis, Australia took the lead on research in this region.”
The digital revolution of the 90s proved a game changer for ocean measurements.
“We saw significant advancements in satellite capability in the 90s and in 1993, for the first time we were able to continuously measure sea levels and ocean circulation with satellite altimetry,” he says.
“The next big transformational technology were Argo floats, robots designed to measure the temperature and salt content of water and first deployed in 2000,” he says. “They are deployed in the ocean where they activate every 10 days for several years, sink to 2km depth, and then take measurements as they rise to the surface where they beam the data back to researchers.”
“With now more than 3,800 floats deployed across the globe, Argo has revolutionised our ability to measure the upper 2km of the ocean,” says Rintoul. “And this will be even further enhanced with new Argo floats developed to measure the deep ocean too.”
Rintoul will be the first to deploy the new deep floats near Antarctica. These floats will allow year-round measurements of the deep ocean to be made on broad scales for the first time.
“We know that the ocean is changing and that these changes are influencing glacial melt rates, sea level rise, and changes to the climate.”
“The Southern Ocean alone takes up around 40 per cent of all the carbon absorbed by the global network of ocean currents,” he says. “But we still don’t fully understand how and why the oceans take up carbon from the atmosphere and this is something the data collected on the voyage will help us better understand.”
Rintoul knows more than most about the ocean and climate. He was the Coordinating Lead Author for the Oceans chapter of the IPCC (Intergovernmental Panel on Climate Change) 5th Assessment Report and has received several high-profile international awards for his work.
“A key question is whether the Southern Ocean’s capacity to soak up heat and carbon dioxide from the atmosphere will continue at the same rate in the future, helping to slow the speed of climate change,” he says. “So far, the answer is not clear.”
“Our measurements will help track how the Southern Ocean is changing and provide new insights into how the region affects climate and sea level, now and for future decades.”
The six week voyage will depart Hobart on January 11 with a team of sixty scientists and crew and is scheduled to return February 21.
Funded by the Australian Government, RV Investigator was commissioned in 2014-15 to replace the 66-metre Southern Surveyor. The 93.9 metre ship is capable of spending up to 300 days a year at sea, and sails from the equator to the ice-edge. It is owned by CSIRO and operated by the Marine National Facility.
You can track the voyage here: http://www.cmar.csiro.au/data/underway/