Simulated response in the El Niño-Southern Oscillation to a weakening Atlantic meridional overturning circulation in the Bergen Climate Model

Lea Svendsen
University of Bergen
Seminar Date: 
16. May 2012 - 10:15 - 11:00
Lecture room, Ground Floor, NERSC

Recently, several studies have simulated a reduction in the strength of the Atlantic meridional overturning circulation (AMOC) due to increased freshwater flux to the northern North Atlantic. The present study investigates the climatic response during a weakening AMOC using a freshwater hosing experiment performed with the Bergen Climate Model. The findings are based on monthly means. The main focus is on the large-scale interannual variability of the El Niño-Southern Oscillation (ENSO), and its connection to the Atlantic. It is found that the characteristic timescales of variability of the ENSO is shifted towards higher frequencies when the AMOC weakens. In addition, during a weakening AMOC there is a stronger correlation between equatorial Atlantic and Pacific SST anomalies when the Atlantic leads the Pacific with about 6 months. These results indicate that a weakening AMOC changes the mean background state of the tropical Atlantic that can result in a stronger connection between the tropical Atlantic and Pacific Ocean. This in turn can alter the variability in the Pacific.