Major ocean currents in the Atlantic Ocean are slowing, and the effects could extend far beyond the Atlantic Ocean. A new study from the University of California, Riverside suggests the change could reduce snowfall in Greenland while strengthening powerful storms along the California coast.
The Atlantic Meridional Overturning Circulation (AMOC) is a vast ocean current system that acts like a planetary conveyor belt. It transports warm tropical water north, helping to keep regions such as Europe relatively calm. As the water cools and becomes denser, it sinks and flows south along the ocean floor.
“It’s well known that the AMOC plays a major role in the global climate system, but its momentum is slowing. What we didn’t know was how the AMOC affects atmospheric moisture and storms outside of the Atlantic region,” said Mohima Mimi, a climate dynamics doctoral student at UCR and lead author of the paper.
“We find that the weakening of the AMOC will result in stronger storms across North America, especially along the California coast, while weakening in Greenland and the Arctic by the end of the century.”
California’s Stronger Atmospheric River
The study, published in the journal Nature Communications, found that a weakened AMOC could change ocean temperatures by changing the amount of moisture the atmosphere can carry. Winds will also strengthen higher up in the atmosphere, potentially causing storms across the Northern Hemisphere.
These stronger winds will cause the storm to move more moisture toward the West Coast and increase the strength of atmospheric rivers.
Atmospheric rivers are long, narrow bands of water vapor that transport moisture from the tropics toward higher latitudes. They provide much of California’s water, but they can also cause severe flooding and widespread damage.
“Atmospheric rivers are a double-edged sword in California,” Mimi says. “They provide much of the state’s water supply, but as they grow more powerful, they are also likely to cause widespread destruction.”
Storm patterns can change around the world
Climate modeling also shows that there are more atmospheric rivers along the east coast of South America and around Antarctica. At the same time, Greenland will experience fewer storms, less snowfall, and slower ice accumulation.
These projected changes manifest in a high greenhouse gas emissions scenario in which the AMOC continues to weaken throughout this century.
Scientists are already seeing signs that the AMOC is slowing as global temperatures rise due to human-induced climate change. Climate models show that the decline is likely to continue if greenhouse gas emissions remain high.
Reducing emissions can reduce impacts
Greenhouse gases primarily come from the combustion of fossil fuels such as coal, oil, and natural gas. Other major sources include methane from livestock such as cattle, deforestation, industrial activities, and waste from sources such as landfills.
Reducing these emissions could limit the impact on AMOC and reduce the influence of ocean currents on future rainfall patterns, said Wei Liu, associate professor of climate change and lead author of the paper.
As atmospheric rivers strengthen, the threat of flooding and infrastructure damage increases. However, it could also provide opportunities to collect additional water if communities improve their forecasts and expand their water storage systems.
Atlantic changes with global implications
The results highlight deep connections within the Earth’s climate system. Changes in one large ocean current can alter rainfall and extreme weather events thousands of miles away, impacting ecosystems, water supplies, and communities across multiple continents.
“This study shows that the impact of AMOC extends far beyond the Atlantic Ocean,” Mimi said. “Understanding these connections can help us better prepare for future water resource changes and extreme weather events.”
