Changing effects of external forcing on Atlantic–Pacific interactions ...

• Main Authors: Karmouche, Soufiane, Galytska, Evgenia, Meehl, Gerald A., Runge, Jakob, Weigel, Katja, Eyring, Veronika
• Format: Article in Journal/Newspaper
• Language: English
• Published: Technische Universität Berlin 2024
• Subjects: 500 Naturwissenschaften und Mathematik550 Geowissenschaften, Geologie550 Geowissenschaften; causal analysis; external forcing; CMIP6; ENSO; climate variability; North Atlantic
• Online Access: https://dx.doi.org/10.14279/depositonce-20705; https://depositonce.tu-berlin.de/handle/11303/21904

Recent studies have highlighted the increasingly dominant role of external forcing in driving Atlantic and Pacific Ocean variability during the second half of the 20th century. This paper provides insights into the underlying mechanisms driving interactions between modes of variability over the two basins. We define a set of possible drivers of these interactions and apply causal discovery to reanalysis data, two ensembles of pacemaker simulations where sea surface temperatures in either the tropical Pacific or the North Atlantic are nudged to observations, and a pre-industrial control run. We also utilize large-ensemble means of historical simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to quantify the effect of external forcing and improve the understanding of its impact. A causal analysis of the historical time series between 1950 and 2014 identifies a regime switch in the interactions between major modes of Atlantic and Pacific climate variability in both reanalysis and ...