ENSO-SAM teleconnections and decadal variability

The El Nino-Southern Oscillation's (ENSO) teleconnection to Antarctica is investigated for modulation by the Southern Annular Mode (SAM). Previously, a dynamical study has shown ENSO-SAM linkages in the observed fields since the International Geophysical Year (IGY) during 1957. The dynamical study found that when ENSO anomalies are "in phase", that is the Southern Oscillation Index (SOI) and the SAM index have the same sign, the ENSO teleconnection to Antarctic latitudes is robust and enhanced. In contrast, when ENSO and SAM are out of phase, the teleconnection between the two is weakened. We now expand the study to include global simulations of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM) versions 3.5 and 4. These recent versions of the NCAR global climate model for the atmosphere contain convective parameterization modifications that improve the simulation of intraseasonal variability, the related Madden-Julian Oscillation and ESNO teleconnections. An idealized multi-year CAM3.5 run forced by observed sea surface temperature (SST) for 1871-2006 was performed by the Climate Variability Working Group at NCAR, and made available by the University of Maryland. The 136-year run has T-85 horizontal resolution and does not include other variable forcing besides SST. Correlation analyses on the indices computed from the CAM3.5 results shows that ENSO statistical relationships, ENSO teleconnections, and SAM events are robust in the CAM3.5 simulation. A striking result is that the anomaly patterns across the extratropics of the Southern Hemisphere appear especially robust in the in-phase case. Therefore, the model results parallel the finding of the dynamical study based upon observed fields. Additional simulations with the NCAR CAM4 enhance the study of ENSO-SAM teleconnections.