Collaborative Research: How Robust Are Common-Era Sea-Level Reconstructions?

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Sea-level rise is one of the most challenging aspects of climate change. In order to be confident in predictions of future sea level estimates, it is important to clearly understand how and why sea level changed naturally in the past. This project will collect field data and perform computer modeling to improve our understanding of the main factors that control average sea level during the Common Era (past ~2,000 years). For example, changes in wind and ocean currents, water temperature, and the rebound of land surfaces caused by removing the weight of ice or sediments all contribute to changes in the record of sea level at any location. This project will examine the origin and nature of uncertainties that enter into sea level reconstructions based on errors in estimating each of these factors in the past. The project will not only help scientists improve our understanding of the causes of sea level changes, but it also will help coastal planners by providing better models for projecting sea-level changes into the future. The project will also support three young scientists, deepening their field, laboratory, and modeling skills.Understanding sea level during the Common Era is central to establishing the uniqueness of modern sea-level rise related to anthropogenic climate change, identifying links between sea level and natural climate variability, and training semi-empirical models of future sea-level rise. Past studies estimate global-mean sea level during the Common Era using proxy records. These estimates differ substantially in terms of global-mean sea-level variability during pre-industrial times. It remains to establish how sensitive these estimates are to various uncertainties, assumptions, and choices involved in producing global-mean sea-level time series from the raw data. A detailed study of the robustness and reproducibility of Common-Era sea-level reconstructions based on field, laboratory, and modeling analyses is proposed. Objectives include: (1) determine the reproducibility of high-resolution salt-marsh sea-level reconstructions; and (2) quantify the robustness of model estimates of Common-Era global-mean sea level. Outcomes will fill basic knowledge gaps, advancing understanding of the Common Era, and leading to better characterization of trends, patterns, and causes of pre- and post-industrial sea-level change. By documenting past spatiotemporal variability of sea level, evaluating associated rates of change during the Common Era, and identifying links to ocean circulation and climate, the project will contribute to achieving the goals and scientific objectives of the Paleo Perspectives on Climate Change (P2C2) program. Efforts will make progress towards the broader goals of sea-level research related to the sensitivity of ice sheets to climate change, the response of the solid Earth to redistribution of ice mass, and the assimilation of proxy records and instrumental observations within a coherent probabilistic framework.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.