Unravelling the secrets of the ocean bed

 The IODP ship JOIDES Resolution which works in the Australian region. Photo courtesy Takuya Sagawa.

The IODP ship JOIDES Resolution which works in the Australian region.
Image courtesy Takuya Sagawa.

The International Ocean Discovery Program (IODP)is a multimillion dollar international geoscience research collaboration, with a mission to progress our understanding of the significant proportion of the earth’s crust that underlies the oceans.

With funding from 23 countries, the IODP operates two fully-equipped research ships, provided by the United States and Japan, that sail to all corners of the world’s oceans, exploring some of the most inaccessible geology of the planet by drilling kilometres deep into undersea sediments and rocks. The Europeans provide an alternative drilling platform once each year, to drill in conditions that do not suit the two regular vessels. With the core samples that are returned to the ship, researchers can unravel the mysteries of plate tectonic events, past and future climate change events, ocean microbiology, and much more.

Australian scientists participate in the program through the Australian and New Zealand IODP Consortium (ANZIC), which receives more than half of its funding from the Australian Research Council—most recently through a $10 million Linkage Infrastructure, Equipment and Facilities grant, awarded in 2016. ANZIC consists of sixteen universities and four science agencies, and the scientifically important contribution of ANZIC scientists ensures that they are lead proponents, or co-proponents, of many IODP proposals in the Australasian region.

Professor Neville Exon, Program Scientist in charge of the Australian IODP Office, explains that our scientists must apply through ANZIC in order get a chance to sail on one of the research vessels.

“The task of ANZIC is to coordinate and rank the Australian and New Zealand applications, before sending them to the US headquarters of the IODP,” he said.

“ANZIC researchers have a great track record of helping design and sometimes leading IODP expeditions, and are automatically allocated at least one place on every IODP expedition sailed, and more on the United States’ ship JOIDES Resolution when it works in our region.”

Professor Exon estimates that about one in three of the scientists on board are early career researchers or PhD students.

“An important part of the role of ANZIC is to encourage science students to get into ocean geoscience. Every year we hold a masterclass for star science undergraduates from universities around Australia and New Zealand.” In these classes, selected students are sent out to sea on a smaller ship, to give them an authentic taste of what it is like to work in ocean geoscience. “We always get fantastic feedback from the students who take these masterclasses,” enthuses Professor Exon.

One early career researcher who has benefited from ANZIC’s work is Jennifer Wurtzel, a PhD candidate at the Australian National University’s Research School of Earth Sciences. Ms Wurtzel recently returned from eight weeks aboard JOIDES Resolution Expedition 363, where she was studying climate variability in a region of the ocean to the north of Papua New Guinea known as the Western Pacific Warm Pool.

“My PhD thesis uses stalagmites from Sumatra to reconstruct tropical rainfall for the last 16,000 years or so. I am particularly interested in a climate event known as the ‘Younger Dryas’, which occurred in the North Atlantic about 12 thousand years ago, but had far-reaching impacts on global climate, showing up as periods of low rainfall in China and Sumatra. We’re still trying to understand its full extent. When ANZIC put the call out for research proposals to go on the ship, I thought ‘Wow that might be really interesting’,” says Ms Wurtzel, whose Master’s thesis was on reconstructing sea surface temperatures, which are closely linked to rainfall, and are reflected by the sediment record beneath the waves.

“The first week on board the ship, we were very busy, just learning how to use the machines. I was in the physical properties laboratory where short sections of core are quickly analysed on scanning tracks for density and magnetic susceptibility. Nearly seven kilometres of core sample were brought up to the ship by the drilling, so we were just constantly carrying cores around. It was exciting to see the changes in the sediments at each site. At the first site, they were all grey mud, but at the next site, there were all sorts of colours and hundreds of ash layers (from nearby volcanic eruptions).”

“There are dozens of technical experts, cooks, officers and engineers as well as about 30 scientists on the ship and we all do 12 hour shifts on and off. Everyone on board is working together intensively,” explained Ms Wurtzel.

“When the ship is in position, it is moved to face the direction of the weather, then as the drilling starts the whole ship shakes and groans,” says Professor Exon, who has participated in several trips throughout his research career. “After the drill makes its way through perhaps 200 metres of ooze on the ocean floor, then it starts to cut into rock. All this is quickly brought up to the ship in nine-metre lengths. These can come up every half an hour or so, and they are immediately split in half and analysed in the ships excellent laboratories.”

Professor Exon says that one of the events in the Earth’s past, which has left distinctive traces around the world, is the impact of the meteor that is thought to have wiped out the dinosaurs at the end of the Cretaceous period. “Even though the impact was on the other side of the planet, near Mexico, it showed up as a ten-metre-thick, fossil-free clay layer in rocks on the Exmouth plateau, off the north west coast of Australia.”

After the expedition, cores are taken on shore for further sampling. Ms Wurtzel plans to focus on a six-metre long section which covers the few thousand years of time that is the focus of her PhD.

“I’m interested in just a few thousand years, but the sediment we cored covers millions of years, so all the Expedition 363 scientists will contribute to reconstructing the full climatic history of the Western Pacific Warm Pool. My work will complement the work of expedition co-chief Yair Rosenthal, who will be doing lower resolution analysis of a longer section.”

In an upcoming trip in 2018, researchers on the JOIDES Resolution will drill for the first time into the Brothers Volcano, an active undersea volcano that has been an object of fascination for many researchers due to its unusual features, including ‘black smokers’—hot vents spewing acidic water into the water column and precipitating mineral deposits on the sea floor, which host exotic types of deep-sea life. Drilling will determine the geological makeup of the volcano, and may also reveal whether valuable metal deposits exist there.

With ongoing ARC support, Australian researchers are guaranteed a position on this and many other future IODP expeditions, and will continue to play a key role in the discovery and analysis of the secrets that lie hidden beneath the deepest reaches of the oceans.