EGU2020-8916
https://doi.org/10.5194/egusphere-egu2020-8916
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Future changes in ENSO teleconnections over the North Pacific and North America in CMIP6 simulations

Jonathan Beverley1, Mat Collins1, Hugo Lambert1, and Rob Chadwick1,2
Jonathan Beverley et al.
  • 1College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, United Kingdom (j.d.beverley@exeter.ac.uk)
  • 2Met Office, Exeter, United Kingdom

El Niño–Southern Oscillation (ENSO) has major impacts on the weather and climate across many regions of the world. Understanding how these teleconnections may change in the future is therefore an important area of research. Here, we use simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to investigate future changes in ENSO teleconnections in the North Pacific/North America sector.

Precipitation over the equatorial Pacific associated with ENSO is projected to shift eastwards under global warming as a result of greater warming in the east Pacific, which reduces the barrier to convection as the warm pool expands eastwards. As a result, there is medium confidence (IPCC AR5 report) that ENSO teleconnections will shift eastwards in the North Pacific/North America sector. In the CMIP6 models, the present day teleconnection is relatively well simulated, with most models showing an anomalously deep Aleutian low and associated positive temperature anomalies over Alaska and northern North America in El Niño years. In the future warming simulations (we use abrupt-4xCO2, in which CO2 concentrations are immediately quadrupled from the global annual mean 1850 value), in agreement with the IPCC AR5 report, the North America teleconnection and associated circulation change is shifted eastwards in most models. However, it is also significantly weaker, with the result that the positive temperature anomalies in El Niño years over North America are much reduced. This weakening is seen both in models with a projected increase and projected decrease in the amplitude of future El Niño events. The mechanisms related to these projected changes, along with potential implications for future long range predictability over North America, will be discussed.

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Presentation version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-8916, Chris Brierley, 07 May 2020

    Hello Jonathan et al,

    I like how you've looked at the mechanisms behind the teleconnection.

    Jo and I include the abrupt-4xCO2 simulations in our past2future ENSO manuscript: https://www.clim-past-discuss.net/cp-2019-155/. I found it hard to reconcile the results of your analysis with ours. We found a weaker teleconnection response in the Southern US, but an amplified response in Canada. I believe that the analysis technique is fairly similar, although we've looked at a composite of ElNino-LaNina. I did compute the El Nino composite though. The codes and the post-processed data can be found at https://github.com/chrisbrierley/PMIP4-enso. The pre-composite detrending likely differs as would the precise make up of the ensemble. We ended up using the default CVDP definitions.

    Chris