EGU24-7849, updated on 08 Mar 2024
https://doi.org/10.5194/egusphere-egu24-7849
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

On the decadal changes of Atlantic-Pacific interactions and the effects of external forcing

Soufiane Karmouche1,2, Evgenia Galytska1,2, Gerald A. Meehl3, Jakob Runge4,5, Katja Weigel1,2, and Veronika Eyring2,1
Soufiane Karmouche et al.
  • 1Institute of Environmental Physics, University of Bremen, Bremen, Germany (sou_kar@uni-bremen.de)
  • 2Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen, Germany
  • 3Climate and Global Dynamics Laboratory, National Center for Atmospheric Research (NCAR), Boulder, CO, USA
  • 4Institut für Datenwissenschaften, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Jena, Germany
  • 5Fachgebiet Klimainformatik, Technische Universität Berlin, Berlin, Germany

We show the results of a study investigating the predominant role of external forcing in steering Atlantic and Pacific ocean variability during the latter half of the 20th (and early 21st) century. By employing the PCMCI+ causal discovery method, we analyze reanalysis data, pacemaker simulations, and a CMIP6 pre-industrial control run. The results reveal a gradual (multi)decadal change in the interactions between major modes of Atlantic and Pacific interannual climate variability from 1950 to 2014. A sliding window analysis identifies a diminishing El Niño-Southern Oscillation (ENSO) effect on the adjacent Atlantic basin through the tropical route, coinciding with the North Atlantic trending toward and maintaining an anomalously warm state after the mid-1980s. In reanalysis, this is accompanied by the prevalence of an extra-tropical pathway connecting ENSO to the tropical Atlantic. Meanwhile, causal networks from reanalysis and pacemaker simulations indicate that increased external forcing might have contributed to strengthening ENSO’s opposite sign response to tropical Atlantic variability during the 1990s and early 21st century, where warming tropical Atlantic sea surface temperatures induced La Niña-like easterly winds in the equatorial Pacific. The analysis of the pre-industrial control run underscores that modes of natural climate variability in the Atlantic and Pacific influence each other also without anthropogenic forcing. Modulation of these interactions by the long-term states of both basins is observed. This work demonstrates the potential of causal discovery for a deeper understanding of mechanisms driving changes in regional and global climate variability.

 

Karmouche, S., Galytska, E., Meehl, G.A., Runge, J.,Weigel, K.,& Eyring,V. (2023b, in review). Changing effects of external forcing on Atlantic-Pacific interactions. EGUsphere, 2023, 1–36. https://doi.org/10.5194/egusphere-2023-1861

How to cite: Karmouche, S., Galytska, E., Meehl, G. A., Runge, J., Weigel, K., and Eyring, V.: On the decadal changes of Atlantic-Pacific interactions and the effects of external forcing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7849, https://doi.org/10.5194/egusphere-egu24-7849, 2024.

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