Future weakening of southeastern tropical Atlantic Ocean interannual sea surface temperature variability in a global climate model

Future changes in the southeastern tropical Atlantic interannual sea surface temperature (SST) variability in response to increasing greenhouse gas concentrations are investigated utilizing the global climate model FOCI. In that model, the Coastal Angola Benguela Area (CABA) is among the regions of the tropical Atlantic that exhibits the largest surface warming. Under the worst-case scenario of the Shared Socioeconomic Pathway 5-8.5 (SSP5-8.5), the SST variability in the CABA decreases by about 19% in 2070-2099 relative to 1981-2010 during the model's peak interannual variability season May-June-July (MJJ). The weakening of the MJJ interannual temperature variability spans the upper 40 m of the ocean along the Angolan and Namibian coasts. The reduction in variability appears to be related to a diminished surface-layer temperature response to thermocline-depth variations, i.e., a weaker thermocline feedback, which is linked to changes in the mean vertical temperature gradient. Despite improvements made by embedding a high-resolution nest in the ocean a significant SST bias remains, which might have implications for the results.

Automated summary

Research using the global climate model FOCI indicates that the interannual sea surface temperature variability in the southeastern tropical Atlantic will decrease significantly in response to increasing greenhouse gas concentrations, especially in the Coastal Angola Benguela Area. Under the worst-case scenario, the reduction in variability is linked to weakened thermocline feedback and changes in the mean vertical temperature gradient. Despite improvements in the model, a significant sea surface temperature bias remains, potentially impacting the results.