CHANGES IN ENSO GLOBAL TELECONNECTIONS THROUGH THE HOLOCENE

The El Niño-Southern Oscillation (ENSO) is one of the primary sources of interannual climate variations around the globe. Observational records of the past two centuries show that the global influence of ENSO via its teleconnections has varied through time, however. In this research, we use the NCAR Climate System Model (CSM) to examine how ENSO global teleconnections could have changed through the Holocene. There are two main motivations for this research. First, our results can be used to improve interpretations of paleoclimate records. It is often unclear whether a proxy has recorded a change in ENSO variability or a change in ENSO teleconnectivity. Model results can separate these two competing influences. Second, this research addresses the larger question of how changes in the base state of the climate affect teleconnections. Answers to this question are critical for predicting how the far-field influence of ENSO could be altered due to future climate change.

We use CSM simulations for five time-slices during the Holocene: pre-industrial time (~1850 A.D.), 3.5 ka, 6.0 ka, 8.5 ka and 11.0 ka before present. Orbital parameters vary between these simulations according to the calculations of Berger (1978). Trace gases are held constant at pre-industrial values. Results from the pre-industrial simulation show that the modeled effect of ENSO variations on global temperature and precipitation patterns is comparable to modern observations. Using all five simulations, we identify regions and time periods with altered relationships between ENSO and temperature or precipitation. We discuss the reasons for changes in these teleconnection patterns and consider the implications for paleoclimate records.