The Role of Anthropogenic Forcings on Historical Sea-Level Change in the Indo-Pacific Warm Pool Region

Detecting and attributing sea-level rise over different spatiotemporal scales is essential for low-lying and highly populated coastal regions. Using the Detection and Attribution Model Intercomparison Project (DAMIP) from the Coupled Model Intercomparison Project Phase 6, we evaluate the role of anthropogenic forcing in sea-level change in the historical (1950-2014) period in the Indo-Pacific warm pool region. We use three models that have at least 10 ensemble members, corresponding to different DAMIP simulations. We determined the changes in regional sea level from both natural and anthropogenic forcings. Our results demonstrate: (a) the emergence of an anthropogenic footprint on regional sterodynamic sea-level change has a large spatiotemporal diversity over the Indo-Pacific warm pool region with the earliest emergence in the western Indian Ocean; (b) a significant rise in dynamic sea level (DSL) (up to 25 mm) and thermosteric (up to 40 mm) sea level over the western Indian Ocean due to greenhouse gas forcing; (c) a positive Indian Ocean Dipole-like pattern in the DSL changes over the tropical Indian Ocean; (d) a significant increase in the halosteric contribution to sea-level rise in the Indo-Pacific warm pool region, and (e) a pronounced rise of manometric sea level (up to 20 mm) over shallow oceans and coastal regions in recent decades. These results provide a comprehensive spatiotemporal analysis of the attribution of anthropogenic factors to sea-level changes in the Indo-Pacific warm pool region. Various natural and human-induced factors contribute to sea-level change, but separating their distinct impacts on a regional to local scale remains challenging. Here we use computer model simulations of global climate to detect and attribute historical sea-level changes (1950-2014) in the Indo-Pacific warm pool region to anthropogenic greenhouse gas and aerosol forcing versus natural forcing. We discovered that the historical rise in sea level is predominantly driven by the influence of greenhouse gases, although aerosols tend to moderate the rate of rise. Notably, the rate of sea-level rise and the time of emergence of anthropogenic signals vary spatially in the region. As an example, anthropogenic signals emerged earlier in the western Indian Ocean in the twentieth century than in the eastern Indian Ocean. Sea-level rise in the deeper oceans of the Indo-Pacific warm pool region is primarily governed by changes in ocean temperature (termed thermosteric) and salinity (halosteric). Conversely, in shallow regions such as over the maritime continent and continental shelves, sea-level rise is primarily a consequence of a local increase in ocean mass (manometric). Our study provides a better understanding of the attribution of regional sea-level changes in the recent past and their possible implications for the future. Historical sea-level changes in the Indo-Pacific warm pool region are attributed using large-ensemble climate model simulations The role of greenhouse gas forcing on historical sea-level changes is dominant, but the time of emergence varies regionally Tropical Indian Ocean dynamics played a key role in controlling historical sea-level changes in the Indo-Pacific warm pool region