A fast atmospheric channel and a slower oceanic one are working as a two-part climate connection between the North Atlantic Ocean and Antarctica, according to a new study published today in Nature. Together, these events created rapid changes in the climate during the last ice age – and could do so again.

“The North Atlantic is sending messages to Antarctica on two different time scales,” said lead author and climate change specialist Christo Buizert in a statement emailed to IFLScience. “The atmospheric connection is like a text message that arrives right away, while the oceanic one is more like a postcard that takes its time getting there – in this case, 200 years, which makes the postal service look pretty good by comparison.”

Applying this same theory means we could see similar “abrupt” changes in our climate that could be further exacerbated by climate change.

The Atlantic meridional overturning circulation (AMOC) is a system of ocean currents that act as a conveyer belt to move water and air, thus creating weather systems and redistributing heat on our planet. Earlier this year, a team of researchers found evidence suggesting that the AMOC is weakening, which could alter the intensification of monsoons, change wind patterns, and lessen the ocean’s ability to take up carbon dioxide.

To study this “communication system”, an international team of scientists examined ice core samples from five different locations in Antarctica, dating them by looking at layers of volcanic ash and measuring changes in prehistoric temperature by analyzing the ratio of water isotopes. By matching them against data from Greenland’s ice core samples, they found that abrupt weather events happened on about 25 separate occasions dating back as far as 100,000 years ago.

“When the Gulf Stream switches on to full strength, Greenland can warm by as much as 10 to 15 degrees Celsius within a decade,” Buizert said. “The change is abrupt and massive. As the ocean transfers heat to the north, the rest of the global ocean starts to cool down. Antarctica eventually ‘notices’ the oceans getting colder, but only after 200 years have passed.”

Generally speaking, the AMOC was very weak during the last ice age, which sent temperatures in the North Atlantic plummeting. Every so often, the AMOC would quickly strengthen, suddenly warming Greenland and changing the responding climate in Antarctica – not once but twice and at a much slower pace.

Now, the world is warming on average, but regional changes depend on how Earth’s atmosphere and ocean circulations respond. Climate models don’t necessarily agree on the specificity of those changes in the future, but this study provides a real-world example of what happened in the past.

“The findings also may have implications for the future,” Buizert noted. “The AMOC is weakening now because of global warming and meltwater from Greenland. The ‘text message’ is being sent and atmospheric conditions are changing. The ‘postcard’ is on the way.”