Ocean water is constantly cycling through the Atlantic ocean through a “global conveyor belt” system scientists call the Atlantic Meridional Overturning Circulation (AMOC). This circulation system is driven by ocean temperature and salinity, slowly bringing warm water north and cold water south. Changes in the AMOC exert a great deal of influence on Earth’s climate and alter nutrient distributions for marine ecosystems. Modeling research has predicted a slow down of the AMOC due to a combination of greenhouse gas emissions and aerosols, but detecting this trend with measurements in real time is difficult due to strong variability signals across decades. A recent study supported in part by the Climate Program Office’s Climate Variability & Predictability (CVP) Program gives evidence that the AMOC has likely been weakening since the 1980’s, and continuing through time at a faster rate. Most past research on this subject has focused on a patch of cooling surface water in the North Atlantic, but this new work, published in Nature Communications, detects this trend by studying salinity in the South Atlantic. The authors show with multiple model experiments that slowing down the AMOC causes salinity to “build-up” in the South Atlantic, which is the trend identified in observations. These results, presented by an international team of scientists including CVP-supported researcher Zhengyu Liu of The Ohio State University and Nanjing Normal University, represent a new way to assess changes in the AMOC that looks beyond the short timescale variability trends. The study also indicates a likelihood that the AMOC will continue to weaken with continual climate impacts in the near future, contributing to an initiative by CVP to advance long-term climate change planning by improving predictions on the decadal scale.
AMOC Weakening Evidence from Salinity “Fingerprint” in the South Atlantic
