Study Sees 50% Rise in Atmospheric Rivers as Weakening AMOC Intensifies North American Storms
Updated
Updated · ScienceAlert · Jul 19
Study Sees 50% Rise in Atmospheric Rivers as Weakening AMOC Intensifies North American Storms
1 articles · Updated · ScienceAlert · Jul 19
Summary
A Nature Communications study projects a slowing Atlantic Meridional Overturning Circulation will strengthen storms across parts of North America by century’s end, with the biggest increase along the Pacific coast from Baja California to Alaska.
NASA atmospheric data and climate simulations linked the weaker ocean current to shifts in atmospheric rivers—narrow moisture bands that can carry up to 15 times the Mississippi’s outflow—by redistributing heat and moisture between hemispheres.
Global atmospheric river frequency could rise about 50%, with wetter impacts expected on South America’s east coast, southern Asia, western Europe, parts of the Pacific and around Antarctica, while Greenland, the Arctic and northern Asia see fewer events.
California faces a sharper version of that trade-off: atmospheric rivers already deliver up to 50% of annual rainfall in the western US but also drive floods, while over West Antarctica they account for 40% to 80% of summer meltwater on ice shelves.
The study says the scale of those changes still depends on future greenhouse gas emissions, underscoring how climate-driven weakening of a single Atlantic current can reshape water resources and extreme weather far beyond the ocean basin.
How does a slowing Atlantic current trigger more extreme storms and flood risk along North America's distant Pacific coast?
As a key ocean current falters, why is the vital system for monitoring its potential collapse facing an uncertain future?
AMOC at Its Weakest in 1,000 Years: Implications for Global Climate and California’s Water and Flood Risk
Overview
The Atlantic Meridional Overturning Circulation (AMOC) is now at its weakest in over a thousand years, with its decline accelerating since the mid-20th century. This weakening, about 15% so far, is mainly caused by more freshwater entering the North Atlantic from melting glaciers and the Greenland ice sheet. The extra freshwater lowers the salinity and density of surface waters, disrupting the sinking process that drives the AMOC. Scientists warn that the AMOC could collapse as soon as 2025 or as late as 2095, which would have major impacts on global climate, including significant changes to California’s weather patterns.