First Study to Relate Antarctic Sea Ice Melt to Weather Change in the Tropics

Photo: Christopher Michel via Creative Commons

Arctic and Antarctic ice loss will account for about one-fourth of the warming that is projected to happen in the tropics, according to a new study published in Nature Geoscience led by Mark England, a polar climate scientist at Scripps Institution of Oceanography at the University of California San Diego, and Lorenzo Polvani, Maurice Ewing and J. Lamar Worzel Professor of Geophysics at Columbia Engineering.

While there is a growing body of research showing how the loss of Arctic sea ice affects other parts of the planet, this study is the first to also consider the long-range effect of Antarctic melt, the research team said.

“We think this is a game-changer as it shows that ice loss at both poles is crucial to understand future tropical climate change,” England said of the study funded by NASA and the National Science Foundation. “Our study will open a hitherto unexplored direction and motivate the science community to study the large effects that Antarctic sea ice loss will have on the climate system.”

“Dozens of recent papers have studied how future Arctic sea ice melting will impact the climate system,” noted Polvani, who was England’s doctoral supervisor. “But the impact of the projected melting of Antarctic sea ice has been ignored. In our new paper, we show that its impact on tropical precipitations is even larger than the melting of Arctic ice.”

The years 2017 and 2018 set records for minimum sea ice extent in Antarctica. England and colleagues from Columbia University’s School of Engineering, Colorado State University, and the National Center for Atmospheric Research in Colorado, used computer simulations to see what scenarios play out near the equator if that decline continues through the end of the century. They found that ice loss combines with Arctic sea ice loss to create unusual wind patterns in the Pacific Ocean that will suppress the upward movement of deep cold ocean water. That will trigger surface ocean warming, especially in the eastern equatorial Pacific Ocean. Warming in that ocean region is a well-known hallmark of the El Niño climate pattern that often brings intense rains to North and South America among other places.

As that surface ocean water warms, it will also create more precipitation. Overall, the researchers believe the ice loss at both poles will translate to a warming of the surface ocean of 0.5℃ (0.9 ℉) at the equator and add more than 0.3 millimeters (0.01 inches) of rain per day in the same region.

“Our paper provides a beautiful example of how interconnected the climate system is,” Polvani adds. “Who would have thought that a large fraction of changes in the tropics can actually be caused by changes by the polar regions?”

 — Columbia Engineering

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