A 30,000 year-old kauri tree in New Zealand is shedding light on global temperature changes, with researchers concluding that a newly identified phenomenon, a 20,000 km-long “atmospheric bridge,” is responsible for connecting melting sea ice in the Antarctic with a quick spike in temperatures in the Arctic during the last ice age. The findings speak to the links between the world’s climate systems, say researchers, particularly with reference to the role played by Antarctic weather in influencing temperatures around the globe.
Climate scientists have known for some time that the Arctic and Antarctic have a long-distance weather relationship with each other, exemplified by what’s called the “bipolar seesaw.” A rapid warming of the climate at one end that produces a resulting cooling at the other, which up until now has been explained by changes in the North Atlantic that cause deep ocean currents (the planet’s “conveyor belt”) to shut down.
But in studying one 400-year-long climate cycle during the last ice age, researchers from Keele University, the University of Tasmania and UNSW Sydney reached a surprising conclusion: while the cooling Antarctic during that period matched up with a warming Arctic, there was no evidence to suggest that deep ocean currents had shifted during that time, meaning that some other system was likely responsible for the dual temperature change.
“Intriguingly, we found that the spike in temperature preserved in the Greenland ice core corresponded with a 400-year-long surface cooling period in the Southern Ocean and a major retreat of Antarctic ice,” said lead author and UNSW scientist Professor Chris Turney, in a press release.
The scientists looked at ancient trees preserved in marshlands in New Zealand to connect ice, marine and sediment records for the time period, finding that lake sediments indicated that there had been a significant change to rain-bearing trade winds over northeastern Australia. Sophisticated climate modelling of the phenomenon confirmed their results, showing that an atmospheric bridge rather than a oceanic conveyor belt was at play, transmitting the change in Antarctic temperatures up to the Arctic.
The researchers see the results as further evidence of the interconnections between climate systems, say the new study’s authors, whose work is published in the journal Nature Communications.
“Our study shows just how important Antarctica’s ice is to the climate of the rest of the world and reveals how rapid melting of the ice here can affect us all. This is something we need to be acutely aware of in a warming world,” Professor Turney said.
Sea ice levels at both poles have been a noted result of global warming, with new record lows reached this year in the Antarctic. In the Arctic, global warming is causing temperatures to rise at a faster rate than other regions on the planet. A recent study of permafrost in Canada’s Northwest Territories found that the warmer temperatures have caused large craters to form in the melting permafrost, which in turn are contributing to global warming by sending more carbon dioxide into the atmosphere.