Stability of ENSO teleconnections during the last millennium in CESM

Abstract

<p>The El Niño-Southern Oscillation (ENSO) has a significant impact on the global climate through atmospheric teleconnections. It is important to understand the stability of ENSO teleconnections, not only for future weather forecasting and climate projection, but also for ENSO reconstructions based on paleo-proxies. In this study, we investigate the decadal variations of ENSO teleconnections in global land surface temperature (LST) from 850 to 2005AD using 13 ensemble members of the Community Earth System Model-Last Millennium Ensemble (CESM-LME). The CESM can simulate the main Eurasian cooling and Arctic warming, known as the warm Arctic-cold Eurasia (WACE) pattern, during the boreal winter of an El Niño. Furthermore, it can also capture the western Antarctic warming during the developing and decaying summers of an El Niño. There is a dominant decadal variation in the ENSO-LST teleconnections, expressed as anomalous LST patterns that closely resemble those seen in the WACE pattern during boreal winter and the western Antarctic warming pattern during summer. This decadal variation of ENSO-LST teleconnections is primarily due to the varying positions of Rossby wave sources associated with distinct ENSO patterns, which are located either to the west or to the east of Hawaii. The LST response to ENSO over South Siberia, as well as the associated precipitation response over North Eurasia, even show opposite patterns at different phases of the decadal variation. The decadal variation in CESM is found to be related to the interdecadal Pacific oscillation (IPO) and is likely attributed to internal variability rather than external forcing. Our findings suggest that the decadal variation in ENSO teleconnections should be considered when using proxies from Eurasian regions to reconstruct ENSO variability.<br></p>