The Shortwave Cloud-SST Feedback Amplifies Multi-Decadal Variability in the Southeast Pacific: Implications for Observed Cooling
Zachary Espinosa, University of Washington
Models struggle to produce SST gradient trends in the tropical Pacific comparable to those seen in nature in recent history. Here, we investigate whether models systematically underestimate internally-generated SST trends by underestimating the feedback of cloud radiative effects on SST gradients. We find that the magnitude of the shortwave cloud-SST feedback in the subtropical southeast Pacific is related to the magnitude of east Pacific multi-decadal SST variability. Using this relationship, we estimate that internal variability in the east Pacific is underpredicted in the majority of models. Adjusting for model bias increases the likelihood of generating a cooling trend at least as large as observations in piControl simulations by between ~10% and ~58%. A heat-budget analysis reveals coupling between cloud-radiative effects, circulation, and SST gradients in driving multi-decadal variability in the East Pacific and suggests that biases in cloud feedbacks may be causing models to underestimate internal SST variability.