High-Resolution Modeling Confirms a La Niña-like Forced Sea Level Response in CESM

Patterns of sea level rise (SLR) and surface warming are tightly coupled, though strong S/N in SLR makes it ideal for identifying forced responses. While climate model ensembles provide an estimate of the forced SLR pattern, standard-resolution models poorly resolve key components of the coupled climate response, including ocean eddies and atmospheric and oceanic fronts. The importance of these small-scale features to regional SLR trends constitutes a major uncertainty in current simulations. Here, the improvements provided through high-resolution (HR) modeling are demonstrated using the recently released MESACLIP experiment, a 10-member ensemble spanning 1920-2100 that is unique for its HR atmospheric (0.25º) and oceanic (0.1º) components. Through comparison with standard-resolution simulations, including a nominal 1º version of the model used in MESACLIP, a fundamental alteration in both the pattern and magnitude of forced regional SLR in the MESACLIP simulations is demonstrated. Agreement between 30-year simulated trends and satellite altimetry is greatly improved and altimeter-era emergence of a La Niña-like forced response is identified in the Pacific and Southern Oceans. These findings suggest that forcing contributes significantly to the ongoing La Niña-like changes in the Pacific ocean and that significant improvements in forced climate change patterns, including those in regional SLR, can be realized through HR climate model ensembles.