Earth's ice ages may have been driven by a hidden ocean chain reaction
Scientists have uncovered a surprising connection between Earth's opposite poles that may help explain how the planet plunged into past ice ages. New research suggests that as massive ice sheets expanded across the Northern Hemisphere, they cooled Atlantic Ocean waters that eventually traveled south toward Antarctica. This cooling may have disrupted Southern Ocean circulation, allowing the ocean to absorb and store…
Key points
- University of St Andrews scientists propose that cooling in the North Atlantic can travel south and alter Southern Ocean circulation, helping store more CO2 and intensify ice ages.
- In computer simulations, cooling only the far northern latitudes produced 74% as much CO2 drawdown as cooling the entire planet.
- Lead author Dr. Madison Shankle said the study demonstrates a plausible mechanism linking Northern Hemisphere ice sheets to Southern Hemisphere ocean changes in model simulations.
Scientists at the University of St Andrews have identified a previously unknown process that may help explain how Earth entered past ice ages, according to a study published in the Journal of Climate. The research links growing ice sheets in the Northern Hemisphere to ocean changes near Antarctica, suggesting cooling in one region could trigger a chain reaction across the planet.
The authors say the connection could explain how northern ice sheets influenced Southern Ocean circulation and sea ice, changes known to reduce atmospheric carbon dioxide, a key factor in ice ages. Until now, scientists had struggled to explain how processes at opposite ends of the planet could be so closely connected.
How the mechanism would work
The researchers propose that as large ice sheets spread across northern regions, they cool nearby waters in the North Atlantic. Over time, these colder waters circulate southward and eventually reach the Southern Ocean.
If the cooling is strong enough, it could alter ocean circulation around Antarctica in ways that store more CO2 beneath the ocean surface. As atmospheric CO2 declines, the planet cools further, potentially helping intensify an ice age.
What the simulations showed
Using computer simulations of ocean circulation, the team cooled only the northernmost latitudes, mimicking the effect of a large ice sheet, rather than lowering temperatures worldwide. Cooling the far north alone produced 74% as much CO2 drawdown as a separate simulation in which the entire planet was cooled.
Lead author Dr. Madison Shankle, from the University of St Andrews School of Earth and Environmental Science, said the study offers evidence of a plausible mechanism connecting Northern Hemisphere ice sheets and Southern Hemisphere ocean circulation changes that lead to CO2 drawdown. She said the work demonstrates the process working in model simulations, which she called a big step forward for the field.
