Collaborative research: Sea-level responses to sediment erosion and deposition over the past 3 million years

点击翻译按钮获取中文摘要

A non-technical description of the project, which explains the project's significance and importanceRising sea level is a concern for coastal communities, regardless of its ultimate cause. This project will more accurately investigate the height of sea level as it was during the mid-Pliocene climatic optimum, approximately three million years ago. This time period is important because atmospheric carbon dioxide had levels of 350 to 450 parts per million and global temperatures were two to three degrees warmer than today. Accordingly, conditions during this episode are analogous to projections of the Earth's future during the next century. Current models of sea level for this time are controversial because of the lack of knowledge about the extent of polar ice that existed. This project will examine three locations where shorelines that formed during the mid-Pliocene climatic optimum are exposed and have wide differences in elevation above present sea level. The main goal is to incorporate the mass of sediment that has subsequently been eroded and redeposited from these uplifted shorelines into numerical models in order to more accurately reconstruct the actual height of sea level during this era and estimate the extent of polar ice. This will provide a tool to better predict the magnitude of future sea-level rise under warming conditions.A technical description of the projectSea-level changes provide an important constraint on ice volumes and polar ice-sheet stability during periods of relative ice-age warmth, including the mid-Pliocene Climatic Optimum (MPCO), the interglacial periods represented by Marine Isotope Stages 5e and 11 (~120 thousand years and ~400 thousand years ago, respectively), and the present. In this regard, the MPCO remains a period of significant interest and contention. Climate models of the MPCO often adopt a eustatic sea level of 25 meters higher than the present-day as a boundary condition, but individual published estimates range from 10-40 meters. Any eustatic value above 10 meters implies major collapse of ice sheets at both poles. Model-based corrections of sea-level markers for glacial isostatic adjustment and mantle flow-induced dynamic topography are available, but the most recent application of these models yields residual elevations for sea-level of MPCO age along the U.S. east coast with large and systematic geographic variability. This proposal focuses on improving existing estimates of eustatic sea level and ice volumes during the MPCO by accounting for sediment redistribution along the US east coast and the southern coastal margins of Australia and South Africa. This research is a novel study at the interface between coastal margin processes and paleoclimate.