edu.ucar.opensky::articles:27283 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-24T18:46:58.623885 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d70869j2 https://doi.org/10.24381/CDS.67E8EEB7 https Related Dataset #1 ORAS5 global ocean reanalysis monthly data from 1958 to present https://doi.org/10.24381/CDS.F17050D7 https Related Dataset #2 ERA5 monthly averaged data on single levels from 1940 to present https://doi.org/10.26024/gtrs-tf57 https Related Dataset #3 CESM2 Pacific Pacemaker Ensemble https://doi.org/10.5281/ZENODO.7747255 https Related Software #1 jakobrunge/tigramite: Tigramite 5.2 https://doi.org/10.5281/zenodo.10408909 https Related Software #2 ESMValTool https://doi.org/10.5281/zenodo.11518925 https Related Software #3 EyringMLClimateGroup/karmouche24esd_AtlanticPacificPacemaker_Causality: Public Release Changing effects of external forcing on Atlantic-Pacific interactions 2024-06-11T00:00:00Z publication https://n2t.org/ark:/85065/d70869j2 https://doi.org/10.5194/esd-15-689-2024 Karmouche, S. author Galytska, E. author Meehl, Gerald A. author Runge, J. author Weigel, K. author Eyring, V. author UCAR/NCAR - Library publisher 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 pacemaker simulations. A sliding window causal analysis reveals a decaying El Ni ntilde;o-Southern Oscillation (ENSO) effect on the Atlantic as the North Atlantic fluctuates towards an anomalously warm state. The causal networks also demonstrate that external forcing contributed to strengthening the Atlantic's negative-sign effect on ENSO since the mid-1980s, where warming tropical Atlantic sea surface temperatures induce a La Ni ntilde;a-like cooling in the equatorial Pacific during the following season through an intensification of the Pacific Walker circulation. The strengthening of this effect is not detected when the historical external forcing signal is removed in the Pacific pacemaker ensemble. The analysis of the pre-industrial control run supports the notion that the Atlantic and Pacific modes of natural climate variability exert contrasting impacts on each other even in the absence of anthropogenic forcing. The interactions are shown to be modulated by the (multi)decadal states of temperature anomalies of both basins with stronger connections when these states are "out of phase". We show that causal discovery can detect previously documented connections and provides important potential for a deeper understanding of the mechanisms driving changes in regional and global climate variability. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. None eng geoscientificInformation