Study Reports 10% Decline in Atlantic Meridional Overturning Circulation from 2004 to 2023

AMOC Decline Observed

A study published in Science Advances found that the Atlantic Meridional Overturning Circulation (AMOC) has declined by approximately 10 percent from 2004 to 2023, based on direct measurements.

The analysis, led by Qianjiang Xing at the University of Miami, examined data over this period and noted an annual weakening rate of about 90,000 cubic meters of water per second. The uncertainty range for the 10 percent change is nearly as large as the change itself.

The study also reviewed pressure changes at three western Atlantic mooring arrays, showing a greater weakening with lower uncertainty.

Buoy measurements confirmed the AMOC weakening at four different latitudes in the western Atlantic.

Measurement Methods and Data Direct

measurements of the AMOC have been conducted for about two decades.

In 2004, the University of Miami and other institutions installed the RAPID-MOCHA array of anchored moorings from the Bahamas to the Canary Islands. This array measures temperature, salinity, and velocity to estimate pressure differences across the Atlantic.

Shane Elipot at the University of Miami stated that water flows from high-pressure to low-pressure areas but is deflected by Earth's rotation, contributing to the overturning circulation.

Additional mooring arrays have been installed since 2004 off the West Indies, the US east coast, and Nova Scotia, Canada. The latest RAPID-MOCHA data analysis supports the observed decline.

Historical Context

and Contributing Factors Analysis

of ocean temperature readings indicates the AMOC has weakened by 15 percent since 1950.

The AMOC transports warm, salty water from the Gulf of Mexico to the north Atlantic, where it cools, sinks, and flows south along the seafloor on the western side. Freshwater from melting Greenland ice sheet dilutes this dense water, slowing the sinking process and weakening the southward flow.