Collaborative Research: P2C2--Constraints on Last Interglacial and Late Holocene Global Mean Sea Level and Fingerprinting Polar Ice Mass Flux from Broadly Distributed Coastal Caves

This project aims to advance the knowledge of global mean sea level (GMSL) and characterize the relative contribution of ice sheets and glaciers to GMSL variations. The researchers will use geological records preserved in cave deposits to reconstruct the GMSL history over the last 130.000-years from multiple locations (Mediterranean Sea, Yucatan Peninsula, Philippine Sea), and to study sea-level high stands during past warm climates.

With over one third of the world’s population living within coastline regions, assessing the regional vulnerability to future-sea level rise is of societal relevance and requires an understanding of the magnitude, rate, and drivers of past sea level fluctuations to put current trends in context. This will be achieved by direct sea level estimates provided by coastline mineralogical records, namely phreatic overgrowth on speleothems which form at sea level on partly submerged caves.

Phreatic overgrowths on speleothems (POS) are precise and accurate indicators of local sea level changes during critical periods of the ice age, including the Mid-Pliocene Warm period, the Last Interglacial (LIG) and the Late Holocene. This project aims to analyze existing POS archives and to expand this archive to include several promising cave sites.

The scientific goals are encapsulated in several core research questions: 1) What is the temporal variability of GMSL from the LIG to the Late Holocene and what is the phasing between peak GMSL and the initiation of global scale warming; 2) What are the relative contributions of the major polar ice sheets to this variability and is there evidence of hemispheric teleconnections?; and 3) to what extent is the GMSL rise and acceleration anomalous relative to the record of GMSL across the Late Holocene? The researchers will develop a near continuous GMSL curve for climate warm intervals derived from high temporally and vertically well resolved POS observations linked to state of the art statistical and geophysical modelling.

The observations include U-series chronologies, high-resolution stable isotope analyses of C and O, and mineralogical and petrographical analyses to constrain timing and duration of peak sea-level high stands. Additionally, numerical simulations of Glacial Isostatic Adjustment (GIA) will be used to correct GMSL record from the impact of GIA.

The potential Broader Impacts (include a greater knowledge and a better understanding of the magnitude and drivers of sea level rise. This has direct implication for different scientific communities investigating key relationships between sea level, ice sheets, Earth’s climate, and properties of the solid earth. Further, the newly developed knowledge will be of a broad societal relevance as it will potentially benefit coastal communities, stakeholders, and policy makers.

This project will provide education and research training for graduate and undergraduate students at the universities of South Florida, New Mexico and Harvard who will be involved in many aspects of the interdisciplinary research. Additionally, the results of this research will be communicated through teaching at the various project institutions. The researchers will disseminate the project findings with the relevant scientific communities via peer-reviewed publication and presentation at national and international conferences.

The research finding will be also disseminated to the broader public through public presentations, popular science articles and media coverage. Educational material will be developed for outreach activities at the studied caves, including underwater images and videos. The data collected during this project will be made publicly accessible.

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.