New study challenges long-held theories of climate variability in the North Atlantic

A study conducted by the Rosenstiel School of Marine and Atmospheric at the University of Miami (UM) challenges mainstream wisdom by identifying the atmosphere as the driver of a decades-long climate variation known as the multidecadal oscillation Atlantic (AMO). The results offer new insights into the causes and predictability of natural climate variations, which are known to cause large-scale global weather impacts, including increased precipitation, droughts and increased frequency of hurricanes in many parts of the basin. Atlantic.

For decades, research on climatic variations in the Atlantic has focused almost exclusively on the role of ocean circulation as a primary driver, particularly the meridional Atlantic overturning circulation, which carries water. warm to the north in the upper layers of the ocean and cold water to the south in the lowlands. layers like a large conveyor belt.

“The idea of ​​the ocean as an engine has been powerful.” said Amy Clement, professor at UM Rosenstiel School, lead author of the study. We used computer models in a new way to test this idea and found that in fact there is a lot that can be explained without ocean circulation. “

While the overall increase in the average Atlantic temperature is caused by greenhouse gases, this study examines the fluctuations that occur within this human-related trend. Identifying the main driver of AMO is essential to help predict global warming of the North Atlantic Ocean in the decades to come due to natural and anthropogenic climate change. Recent research suggests that a warm phase of AMO has been in effect since the mid-1990s, which caused changes in precipitation in the southeastern United States and resulted in the transformation of twice as much. from tropical storms to hurricanes only during cold phases.

Using multiple climate models from around the world, Clément’s research team removed ocean circulation from the analysis to reveal that variations in the Atlantic climate were generally the same. AMO results in a horseshoe-shaped model of ocean surface temperatures in the North Atlantic Ocean that have occurred naturally over the past 1,000 years on time scales of 60 to 80 years. This new analysis shows that the AMO model can be explained by atmospheric circulation alone, without any role for ocean circulation.

“These results require us to rethink our ability to predict decade-wide temperature fluctuations in the Atlantic and their associated impacts on land. Many changes may have limited predictability, which means that we should be prepared for a range of climates associated with global warming, ”said Clement.