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Antarctica’s future is detected in its past

Bella Duncan during her research trip to Antarctica at the beginning of her PhD research. PHOTOS/SUPPLIED

Can you imagine Antarctica covered in a lush green sub-tropical forest? Well, Carterton woman Dr Bella Duncan can.

Duncan, a Victoria University research fellow in organic geochemistry, has been tracking Antarctica through time as carbon dioxide levels and temperatures changed.

Her research shows a very different picture of Antarctica from the hunk of ice many imagine it to have always been.

Duncan said she had always been interested in geology, a curiosity passed down from her father.

“From a young age, I was having chats about that kind of thing with him. In my teens, I had a National Geographic subscription.”

Duncan went from life in Masterton to studying geology and geography at university, where she was introduced to the world of Antarctica.

She said she enjoyed the idea of reconstructing the ice continent’s past climate and understanding what the earth had looked like millions of years ago.

“Geology is almost like storytelling; it’s telling earth’s story.”

Duncan studied previous ocean change in New Zealand for her master’s and took on an Antarctic-focused project for her doctor of philosophy [PhD].

“My research looks at times in the past when we had higher atmospheric carbon dioxide and higher temperatures and investigates what Antarctica looked like during those times.

“How much ice was there? What were ocean temperatures like? Was there vegetation?” she asked.

A 35 million-year-old fossil Nothofagus leaf that Duncan found during her trip to Antarctica.

Duncan used historical data to form a better understanding of what might happen to the South Pole continent as human-induced climate change increases atmospheric carbon dioxide and temperatures.

“At the level we’re at today, about 400 parts per million [ppm] of carbon dioxide, there was quite a lot less ice. There were times when the sea levels were up to 20 metres higher than today.”

She said even small amounts of vegetation were present in Antarctica.

When carbon dioxide levels were tracked back even further to 500ppm, tundra [grasses, mosses, and lichens] covered many parts of Antarctica, and ocean temperatures were about five degrees warmer than they are today.

She said the icy Antarctic world became almost unimaginable once carbon dioxide reached 1000ppm, with vegetation more similar to New Zealand’s beech forests.

According to Yale University, atmospheric carbon dioxide ranged from 1000ppm to 1600ppm during the mid-to-late Eocene, from 33.5 to 55 million years ago.

The Eocene marked the first appearance in the fossil record of the two marine mammal groups, the cetaceans [whales, porpoises, and dolphins] and the sirenians, similar to modern manatees and dugongs.

Duncan said the hotter the world was and the more carbon dioxide it had, Antarctica’s vegetation became more and more similar to tropical forests.

“About 50 million years ago when we had over 1000ppm, some of the plant fossils and pollen found are similar to palm trees that are found in Indonesia now.”

Research published in Nature Geoscience by Duncan and her team gave further evidence earth may be nearing a “tipping point”.

“Our findings indicate we’ve crossed a threshold where increased carbon dioxide means oceans will warm to a level where there is major ice loss at the marine margins of Antarctic ice sheets, resulting in global sea-level rise over the coming decades and centuries,” Duncan said.

Duncan and her team used molecular fossils from core samples taken during ocean drilling projects to inform their findings.

She said within 100 years, the world would see rapidly escalating change with emissions continuing to increase, and there would undoubtedly be much less ice on Antarctica.

“There’s a lot of melt around the margins now; we’re seeing that melt accelerating.”

However, she said it would take several hundred years to a thousand years for massive amounts of ice loss and vegetation to return to the land.

“But that’s the sort of Antarctica that we commit to if we don’t reduce emissions.”

Duncan said although climate change has varied because of natural processes in the past, this time, it was being driven by humans.

She said the rate of climate change that was happening now was much faster than what had been seen in the past.

“Because we’re moving so rapidly at the moment, we’re trying to understand how fast these changes might start happening.

Duncan said the big scientific question was how fast Antarctica would respond to climate change.

Grace Prior
Grace Prior
Grace Prior is a senior reporter at the Wairarapa Times-Age with a keen interest in environmental issues. Grace is the paper’s health reporter and regularly covers the rural sector, weather, Greater Wellington Regional Council, and coastal stories.

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