Antarctic voyage to study ocean warming

Tuesday 28 February 2017
The CSIRO Investigator on Antarctic seas. Photo: Asaesja Young

By Georgina Connery, The Canberra Times

He has searched vast stretches of the Antarctic sea floor and battled the elements to hunt down clues that are more than 30,000 years old.

Australian National University researcher Dr Brad Opdyke is confident his challenging fieldwork on board the CSIRO's Investigator will provide the necessary evidence to show why our world's oceans temperatures are rising.

The paleoceanographer's theory is that sea ice melting in the Northern Hemisphere is reducing deep water formation in the North Atlantic, which in turn impacts the ocean currents responsible for heat exchange between the two hemispheres. 

To prove it he and his team are deploying winches to depths of up 3.5 kilometres through frigid Antarctic seas, drilling into the sea floor and hauling samples back up to the boat. 

"It is a theory that has been around for a long time," he said. 

"During these cooling events, known as Heinrich events, the formation of deep water in the North Atlantic, just south of Greenland, slows down and nearly stops. It really reduces the heat exchange between the northern and southern hemisphere."

Sea warming magnified by this cycle was likely to boost overall temperatures by one degree in temperate and sub-tropical regions. 

"It doesn't sound like a lot," he said. 

"But for ecosystems like the Great Barrier Reef, which are sitting right at their thermal maximum right now, that is really significant and could be devastating." 

What Dr Opdyke calls "playing in the mud" is his team closely examining ancient fossils of zooplankton, looking at the stable isotopes of carbon and oxygen locked up in these micro-fossils and searching for patterns of sea warming over the past 30,000 years. 

"What I am looking for around these specific time intervals is indications that it did get warmer," he said.  

"It is these time intervals we are really concentrating on to try and predict what is going to happen over the next few decades." 

Dr Opdyke will end his second voyage to the Antarctic on March 5 when the Investigator docks in Hobart.

The expedition data will, along with ice core samples, coral cores and other environmental samples, help to fine-tune current climate modelling. 

However, Dr Opdyke hoped providing new evidence of the climactic interplay between the northern and southern hemispheres would lead to a more cooperative stance in tackling climate change.

"There is no doubt the earth is warming because of anthropogenic CO2 and greenhouse gasses in the atmosphere. That is a battle that has moved from being a scientific question to a public policy one," he said.

"What I will be saying if we find evidence for warming during these time intervals, is that this is another pressure that will be added to the Great Barrier Reef.

"Some people would argue we don't need any more evidence about the dangers to the Great Barrier Reef, but this would just be another example of how global climate change, in the big picture, is impacting the Australian region." 

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