Scientists at St Andrews University have uncovered the secret of what ended the last ice age.
It has been long-known that a rise in atmospheric carbon dioxide gas (CO2) pushed up global temperatures and help put an end to the last ice age about 15,000 years ago.
But boffins had been in the dark about what caused the release of CO2.
They now know it was stored in the deep Southern Ocean around Antarctica and was released into the atmosphere as the ice age ended released into the atmosphere as the ice age ended, linked to pulses of rapid climate change and melting sea ice.
The findings were published in the science journal Nature on Thursday.
Led by Dr James Rae from the School of Environmental and Earth Sciences at St Andrews, the study provides crucial evidence of the processes that controlled CO2 and climate during ice ages.
Dr Rae said: “Many scientists suspected that the ocean round Antarctica was responsible for changing CO2 levels during ice ages, but there’s not previously been data that directly proved this.”
As well as helping scientists better understand the ice ages, the new findings also provide context to current CO2 rise and climate change.
Dr Rae added: “Although the CO2 rise that helped end the last ice age was dramatic in geological terms, CO2 rise due to human activity over the last 100 years is even larger and about 100 times faster.
“CO2 rise at the end of the ice age helped drive major melting of ice sheets and sea level rise of over 100 metres.
“If we want to prevent dangerous levels of global warming and sea level rise in the future, we need to reduce CO2 emissions as quickly as possible.”
Using samples of fossil deep sea corals, brought up from 1000 meters below the sea surface, Dr Rae and his team made chemical measurements that allowed them to reconstruct the CO2 content of the deep ocean.
The researchers found that the deep ocean CO2 record was the “mirror image” of what was in the atmosphere, with the ocean storing CO2 during an ice age and releasing it back to the atmosphere during the thaw.
Professor Laura Robinson from the University of Bristol, who collected the samples from the Southern Ocean, added: “CO2 rise during the last ice age occurs in a series of steps and jumps associated with intervals of rapid climate change.
“Deep sea corals capture information about these climate changes in the chemistry of their skeletons but are hard to find.”
To bring back these important samples, the team spent months in the freezing waters of the Drake Passage, between South America and Antarctica.
Dr Andrea Burke from St Andrews, who was part of the mission, said: “Most people think of corals as tropical creatures, but they also live deep beneath the waves in some of the world’s most extreme deep-sea environments.”