THE INFLUENCE OF THE PACIFIC OCEAN BASIN ON RECONSTRUCTIONS OF OCEAN BASIN VOLUME AND GLOBAL SEA LEVEL FLUCTUATIONS

The fluctuation in the volume of ocean basins is a primary driving force for long-wavelength changes in eustatic sea level in an ice-free world, i.e. most of the Mesozoic and Cenozoic. Ocean basin volume is largely dependent on changes in seafloor spreading history, which can be reconstructed based on an age-depth relationship for oceanic crust and an underlying global plate kinematic model. The Pacific Ocean basin (and its pre-cursor, Panthalassa) has persisted as the largest ocean basin throughout the Mesozoic and Cenozoic, and is a significant driver of sea level dynamics. However, the long history of circum-Pacific subduction has resulted in the loss of early oceanic crust, requiring the modeling of synthetic ocean crust for large regions of the Pacific basin throughout geologic time. Furthermore, despite geological evidence supporting the presence of numerous back-arc basins throughout the Mesozoic and Cenozoic, kinematic models of back-arc basins in the Pacific Ocean basin are incomplete and focus mainly on the Cenozoic.

We assess the uncertainty in deriving ocean basin volume based on a global plate kinematic model since 230 Ma, and compare the influence of the Pacific Ocean basin to the Atlantic and Indian Ocean basins. Since the Pacific basin is based on predominantly synthetically restored ocean crust during the Mesozoic, we assess uncertainties arising from changes in plate boundary configuration on the mean age, depth, and volume of ocean basins. We also investigate the influence of poorly constrained features (e.g. LIPs, back-arc basins) on the volume of the Pacific basin, by assessing their characteristics at present-day and during well-constrained times during the Cenozoic. Further, we derive a global sea level curve based only on the reconstructions of ocean basin volume (i.e. excluding effects such as dynamic topography and glaciation), and present the influence of each ocean basin and uncertainties through time. We find that by incorporating reasonable predictions for these components during times where ocean basins are predominantly synthetic reconstructions, the mean depth of ocean basins shallow by over 150 m. Such investigations are important for exploring Earth’s evolutionary cycles including transitions from Greenhouse to Icehouse worlds, and continental amalgamation and dispersal.