The stark climate differences between the North and South Poles can be baffling. One may see sea ice retreating, while it expands at the other. But, if they’re both extremely cold, shouldn’t they behave similarly? Not according to researchers at Oregon State University, who say they’ve found an oceanic link between the two hemispheres. Abrupt climate changes first recorded in Greenland will reliably reach Antarctica 200 years later, due to oceanic oscillation.
“The fact that temperature changes are opposite at the two poles suggests that there is a redistribution of heat going on between the hemispheres,” said Christo Buizert, a post-doctoral research at Oregon State University and lead author on the study. “We still don’t know what caused these past shifts, but understanding their timing gives us important clues about the underlying mechanisms.”
What led them to the conclusion was an ice core drilled in West Antarctica in 2011. Drilled to a depth of over 3,000 meters, the core gives a very detailed timeline of climate changes over the past 68,000 years. The core location was carefully selected for the site’s combination of thick ice and heavy annual snowfall. The sample’s quality was such that researchers were able to identify 18 distinct abrupt climate changes over the past 68,000 years. With Greenland’s climate history well-established, the researchers were able to see that changes in Greenland were felt 200 years later in Antarctica.
“Previous work was not precise enough to determine the relative timing of abrupt climate change in Antarctica and Greenland, and so it was unclear which happened first,” said Eric Steig, a professor in the Department of Earth and Space Sciences at the University of Washington, who co-wrote the paper. “Our new results show unambiguously that the Antarctic changes happen after the rapid temperature changes in Greenland. It is a major advance to know that the Earth behaves in this particular way.”
The long lag between the hemispheres leads the researchers to believe there’s an oceanic element at play. As temperatures rise in the north, that heat gets stored in the seawater. As they cool, they sink, and something called the Atlantic Meridional Overturning Circulation (AMOC) circulates them from north to south. Because this is a slow process, the scientists believe that this may be the driver of the north-south climate relationship.
“The fact that temperature changes are opposite at the two poles suggests that there is a redistribution of heat going on between the hemispheres,” said Buizert. “We still don’t know what caused these past shifts, but understanding their timing gives us important clues about the underlying mechanisms.”
The researchers note that the climate changes they’ve observed in the past were different from what we’re experiencing today. Those changes were regional and driven by abrupt changes in ocean circulation. Today, however, climate changes are global and driven by the addition of greenhouse gasses to the atmosphere.