Simulations of the edge of the Western Pacific Warm Pool in CMIP5, and the implications for climate change and ENSO dynamics

A report from the 1st meeting of the Western Pacific Warm Pool Task Force is given, followed by an exploration of the equatorial edge of the western Pacific warm pool. The edge of the Warm Pool separates warm fresh water from cooler saltier water. Its simulation and how it might change, has implications for marine habitats, rainfall and ENSO dynamics. The simulation of the edge is examined in 19 CMIP5 models, over the historical period and the RCP8.5 scenario. The edge is defined by the isotherm associated with the maximum sea surface salinity gradient. The simulation of the edge has implications for how a model can reproduce ENSO dynamics and is an important component of various paradigms: Delayed Action Oscillator, Advective-Reflective oscillator, and zonal-advective feedback. Projected warming is revisited by examining changes relative to the edge. The spread in simulated warming associated with point-wise projections at specific physical locations is reduced when considering changes with respect to the edge of each model’s warm pool. Moreover, the pattern of warming is sensitive to how well the warm pool is simulated.