Investigating the Impact of Climate Variability and Change on the California Current System Using a Pacific Pacemaker Experiment

Ocean-atmosphere teleconnections driven by the El Niño-Southern Oscillation (ENSO) can have significant impacts on the physical and biogeochemical ocean properties of the California Current Large Marine Ecosystem (CCLME), one of the world’s major upwelling regions that supports important marine resources. This study aims to deepen our understanding of the impacts of ENSO on the ocean processes that influence marine ecosystems in the CCLME. This is accomplished using a Tropical Pacific Pacemaker Ensemble from the Community Earth System Model 2 (CESM2), a climate model in which 10 members have sea surface temperature (SST) anomalies in the eastern tropical Pacific that are nudged to observations from 1880 to 2020, thus capturing the observed ENSO signal. These 10 simulations demonstrate 10 different realizations of natural or internal variability in the climate system, including the varied influence of ENSO on the CCLME. We show the statistical relationships and uncertainties between the Niño-3.4 index and multiple physical and biogeochemical ocean properties in the CCLME. We quantify the maximum lag correlation between the Niño-3.4 index and monthly CCLME anomalies, including SST, which has an ensemble mean lag time of 6 months and an ensemble spread ranging from 5 to 8 months. We also demonstrate the expected lagged response of the CCLME to ENSO events by quantifying the correlation between the wintertime Niño-3.4 index and the following springtime CCLME anomalies, with SST having a median correlation value of 0.4 and a spread between -0.2 and 0.7. Results from this study demonstrate the uncertainty in the ENSO-CCLME connection, with the potential to help inform resource management here.