Researchers have been examining changes in the Atlantic Meridional Overturning Circulation, known as the AMOC, a system of ocean currents that carries warm, salty water north toward Greenland and moves colder water south. The current plays a key role in redistributing heat across the globe.
"AMOC has been slowed down, and projections suggest that it will further weaken in future climate scenarios by the end of 21st century," UC Riverside researcher Mohima Sultana Mimi said.
Scientists monitor the circulation using observation buoys in the Atlantic Ocean.
"There are observation buoys in the Atlantic Ocean that measures the volume transport in the Atlantic that is coming from north to south and by calculating the volume transfer, we can measure the strength of this current," Sultana Mimi said.
According to researchers, a weakening AMOC can disrupt the balance between warm and cold ocean waters, leading to warmer water near the equator. Those changes can affect weather systems by influencing hurricane development and altering wind and rainfall patterns.
"When the AMOC weakens, it strengthens the prevailing winds in the North Pacific. that further drives atmospheric rivers to the West Coast of North America," Sultana Mimi said.
What does this mean for California?
Atmospheric rivers transport large amounts of water vapor over long distances and can bring significant rainfall to California.
While those storms can help replenish reservoirs and ease drought conditions, stronger systems also can increase the risk of hazardous weather.
"When the intensity becomes higher, from Category 3 to Category 5, then the effect of the atmospheric rivers will become hazardous. That means frequent flooding, flash flood, extreme precipitation, extreme snowfall during," Sultana Mimi said.
Changing weather patterns like El Niño are studied months ahead and can usually be a good indicator of potential weather conditions, but the intensity of the storms -- or even landfall -- may be much harder to predict.