New research has uncovered a process which may have helped drive the Earth into past ice ages.
Published by the University of St Andrews, their paper links ice sheets in the Northern Hemisphere to changes in ocean circulation and sea ice in the Southern Hemisphere – which drives down atmospheric CO2.
Given they are quite literally a world apart, it has been a long challenge to link the two features together.
Earth was mainly driven into ice ages by more CO2 being stored in the ocean, which is a process largely driven by changes in the Southern Ocean around Antarctica. How the initial growth of large ice sheets in the Northern Hemisphere then led to changes in the Southern Ocean, ending up in CO2 drawdown, was unknown until now.
The researchers proposed and tested their hypothesis that once northern ice sheets start to grow, they cool nearby North Atlantic waters, which eventually circulate all the way down to the Southern Ocean.
If the cooling of the northern waters is strong enough, it could induce significant circulation changes in the south, which is known to lead to more CO2 being stored in the ocean.
Lead author Dr Madison Shankle, from the School of Earth and Environmental Science, said: “Essentially, we’ve produced evidence of a plausible mechanism connecting these two far-flung puzzle pieces – Northern Hemisphere ice sheets and Southern Hemisphere ocean circulation changes leading to CO2 drawdown – which has been a tricky thing to explain in our theory of Earth’s past ice ages. Our study takes the step of actually demonstrating them working in model simulations, which is a big step forward for this field.”
Historically, scientists studying ice ages have long focused on the Southern Ocean – yet the ice ages are natural case studies of how carbon moves in and out of the atmosphere. That means the more we know about them, the more researchers can understand how Earth naturally moves carbon around in the carbon cycle.
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