Intrinsic Century-Scale Variability in Tropical Pacific Sea Surface
Temperatures and their Influence on Southwestern US Hydroclimate
Abstract
Hydroclimate variability of the southwest United States (SWUS) is
influenced by the tropical Pacific Ocean, particularly the phase of the
El Niño/Southern Oscillation (ENSO), via teleconnections, which are
expected to be altered by climate change. However, natural variability
in this teleconnection has not been robustly quantified, complicating
the detection of anthropogenic climate change. Here, we use a linear
inverse model (LIM) to quantify natural variability in the ENSO-SWUS
teleconnection. The LIM yields realistic teleconnection patterns with
century-scale variability in teleconnection strength comparable to
simulations from the Last Millennium Ensemble project and the Coupled
Model Intercomparison Project Phases 5 and 6. The variability quantified
by the LIM illuminates two aspects of our understanding of ENSO and its
impacts: the inherent statistics of the observable system can produce
century-long periods of nonsignificant correlation, and detecting
changes in ENSO-related hydroclimate variability is challenging in a
changing climate.