Seminar by Ingo Richter from Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
28 July 2025
KST 14:00
The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.
Recent studies examining CMIP6 projections have indicated that equatorial Atlantic interannual variability (also known as the Atlantic zonal mode or AZM) will weaken under global warming. This has been associated with a weakened Bjerknes feedback resulting from the stabilization of both the atmosphere and ocean. In the present study, we take a closer look at how these constraints influence the evolution of individual AZM events and their linkage to the tropical Pacific. The results confirm that the AZM weakens under increased greenhouse gas forcing but also suggest that its basic mechanisms are relatively robust. There is, however, a tendency for a secondary variability peak in boreal spring, in addition to the present-day peak in summer. Analysis suggests that this is due to stronger thermodynamic influences from the tropical Pacific.
Observations indicate that the AZM has weakened and become less predictable over the last few decades. This could be interpreted as early signs of the impacts of climate change. The CMIP6 projections, however, do not support this. The observed amplitude changes are far greater than the subtle decline projected by the models. Furthermore, predictability in the models is little affected by increasing greenhouse gas concentrations. Thus, the observed changes must be due to different causes. Alternatively, the CMIP6 models do not realistically represent the effects of greenhouse gas forcing on the AZM.