ESP GUEST SEMINAR - Thursday, 26 January, 2 pm

[Earth System Physics Section]

Earth System Physics
SPECIAL GUEST SEMINAR
Thursday, 26 January 14:00 hrs
Common Area, 2nd floor, exSISSA bldg.
and on Zoom

*Prof. Noel Keenlyside***
Geophysical Institute,
University of Bergen and Bjerknes Centre for Climate Research

*/Tropical Atlantic forcing of different ENSO regime/*

Abstract:
/The El Ni//ñ//o Southern Oscillation (ENSO) underwent a major shift in 
in the 1970’s, becoming stronger and more predictable. This shift has 
been attributed to changes in the tropical Pacific mean state. However, 
around the 1970’s, tropical Atlantic–Pacific variability became coupled, 
with Atlantic SST leading opposite signed changes in the Pacific by 
around 6-months. Here we assess the role of the Atlantic in driving the 
ENSO regime shift using pacemaker experiments with two climate models: 
ECHAM5/MPIOM and SPEEDY/RGO. In these experiments, model SST is restored 
to observations in the tropical Atlantic, while elsewhere the models are 
fully coupled. Both models capture the observed changes in inter-basin 
interactions and strengthening on ENSO variability after the 1970’s. The 
warming of the equatorial and south Atlantic and southward shift of the 
inter-tropical convergence zone causes inter-basin interactions to 
become active after the 1970’s in the models. In ECHAM5/MPIOM, this 
leads to Atlantic Ni//ñ//o variability driving increased ENSO activity. 
In SPEEDY/RGO, the increase in ENSO activity appears more related to 
induced mean state changes in the Pacific./

ID: 943 6414 4154
PSW: 311357
Link: https://zoom.us/j/94364144154