CoAuthors

Philip Thompson (University of Hawaiʻi, United States)

Herein global and regional spatial patterns of sea-level change in the altimeter record are compared to contemporaneous (1993-2014) patterns of change from state-of-the-art climate models. A multi-model ensemble of Coupled Model Intercomparison Project phase 6 (CMIP6) historical simulations are analyzed (n = 167) and a weak and largely zonally homogenous pattern of change is found in the ensemble mean. While some CMIP6 simulations have regional patterns of change that are a close match to the altimeter record, none are a good match globally (maximum centered pattern correlation statistic globally of 0.40 and 5-95% range of -0.20-0.26). Our focus in this study is on differences in patterns of change across the individual historical simulations and the role for internal variability, external forcing, and structural factors in driving these differences. For instance, a close linear relationship is found between patterns of change in sea surface temperature (SST) and those in sea level, and both patterns can be related to the trajectories of common modes of atmosphere-ocean variability, with hotspots in the tropical Indian Ocean and the Pacific Ocean globally. Using pre-industrial control simulations (with no transient external forcing and from the same climate models) we determine where external forcing, principally anthropogenic in origin, has and will produce trends that are significant relative internal variability. At present, climate models suggest that trends over of 26.8% of ocean area have emerged from internal variability (5-95% range of 16%-37%), with this number increasing to 34.5% by 2040 (5-95% range of 24%-47%) and with little sensitivity to emission scenario.