Atlantic Ocean Current Will Weaken Only Moderately With Climate Change, Finds Caltech Study

(MENAFN- AsiaNet News) <p>The Atlantic meridional overturning circulation, or AMOC, is a system of ocean currents in the Atlantic Ocean that helps regulate Earth's climate by moving heat from the Southern Hemisphere to the Northern Hemisphere. </p><p>It influences regional weather patterns, including Europe's mild summers and the monsoon seasons in Africa and India. Climate models have long warned that global warming could cause the AMOC to weaken significantly, possibly leading to serious climate effects such as higher sea levels and colder weather in northern Europe.</p><p>However, new research from Caltech shows that while the AMOC will weaken due to global warming, this weakening is likely to be much less severe than many current climate models predict.</p><p>The Caltech team created a simplified physical model based on core ocean circulation principles and combined it with real-world data collected over 20 years from monitoring systems in the Atlantic Ocean. Their findings suggest the AMOC will weaken by about 18 to 43 percent by the end of this century. This means the AMOC will still weaken, but not as dramatically as some previous studies suggested.</p><p>This study helps reduce uncertainty about the future strength of the AMOC, a question that has puzzled climate scientists for years. The research was carried out in Caltech laboratories led by Professors Tapio Schneider and Andrew Thompson, both experts in environmental science and engineering.</p><p>Historical records from ocean sediments show that the AMOC has weakened before, such as during the Last Glacial Maximum about 20,000 years ago, which caused major climate changes in North America and Europe. Today's climate models vary widely in their predictions of how much the AMOC will weaken this century. Some suggest large declines, while others predict only small changes. Former Caltech graduate student Dave Bonan led this study to better understand why these differences exist.</p><p>The team discovered that climate models with a stronger present-day AMOC tend to predict greater weakening in the future. This is because a stronger AMOC usually reaches deeper into the ocean, making it more sensitive to changes caused by warming and freshwater inflow at the surface. In contrast, models with a shallower AMOC predict less weakening.</p><p>Using this insight, the researchers combined their simplified model with real observations to narrow down the range of possible future changes. They concluded that even under high-emission scenarios, the AMOC will likely weaken only moderately. The study also points out that some past extreme predictions were influenced by climate models incorrectly simulating ocean conditions.</p><p>Dave Bonan, now a PhD graduate, emphasized,“Our results suggest the AMOC will experience a limited decline rather than a drastic drop during this century.” He also highlighted the importance of using higher-resolution climate models in the future, which may offer better details about the AMOC and improve predictions.</p><p>This research was funded in part by the National Science Foundation Graduate Research Fellowship Program (NSF-GRFP), which Bonan credits with allowing him the freedom to explore fundamental questions in climate science.</p><p>The paper, titled“Observational constraints imply limited future Atlantic meridional overturning circulation weakening,” was published in Nature Geoscience. Along with Bonan, Schneider, and Thompson, co-authors include Laure Zanna from New York University, Kyle Armour from the University of Washington, and Shantong Sun from Laoshan Laboratory in China. Funding also came from the NSF, the David and Lucile Packard Foundation, and Schmidt Sciences LLC.</p>

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