Stability of ENSO teleconnections during the last millennium in CESM

Abstract El Niño-Southern Oscillation (ENSO) poses large impacts on global climate through atmospheric teleconnections. Understanding the stability of ENSO teleconnections is not only important for future weather forecast and climate projection, but also for paleo-proxy based ENSO reconstructions. In this study, we explore decadal changes in ENSO teleconnections on global land surface temperature (LST) from 850 to 2005 AD using 13 ensemble members of the Community Earth System Model-Last Millennium Ensemble (CESM-LME). The CESM can simulate the main cooling in Eurasia along with a warming Arctic over northern Canada and Greenland, known as the warm Arctic-cold Eurasia (WACE) pattern, during the boreal winter of an El Niño, as well as western Antarctic warming during El Niño developing and decaying summers. The decadal changes in ENSO teleconnections on LST show large anomalies with pattern highly similar to WACE and western Antarctic warming in winter and summers, respectively. The decadal changes are mainly caused by ENSO precipitation-excited Rossby wave source to the west or east of Hawaii, and LST response over South Siberia to ENSO and associated precipitation response over North Eurasia can even reverse sign during different phases of this decadal variability. The decadal changes in CESM may be related to the interdecadal Pacific oscillation (IPO) and thus are likely attributed to internal variability rather than external forcing. Our results suggest that the decadal variability in ENSO teleconnections should be considered when reconstructing the ENSO using proxies from the Eurasian regions.