NSF Award
2420274
The permanence of Earth’s ice sheets is threatened by ongoing climate change, yet modern observations only inform understanding of ice sheet processes for the past few decades. Because ice sheets have a response time of hundreds to thousands of years, it is imperative to gain this longer-term perspective. Ice-rafted debris – the sediment entrained beneath ice sheets and exported to the ocean floor by melting icebergs – is commonly used as a tool for reconstructing ice sheet behavior over thousands to millions of years. In sediments found at the bottom of the North Atlantic Ocean, layers of abundant ice-rafted debris have been identified and associated with times when ice sheets destabilized in the past. Interpretation of these records is nevertheless hindered by a lack of interpretative tools that enable linking ice-rafted debris more accurately to its source ice sheet. This research will develop and employ a novel data-assimilated modeling approach that integrates geochemical ice-rafted debris data into iceberg simulations for the first time. Development of this tool aims to clarify interpretations of ice-rafted debris in the North Atlantic basin by disentangling the source(s) of these materials during ice sheet destabilization events in the past. Results from this work offer to inform our understanding of ice sheet sensitivity to climate changes. This project will also lay the groundwork for future projects seeking to better constrain the pathways ice-rafted debris and in turn improve interpretations of these data for ice sheets in other ocean basins. This project will fund the professional development of a postdoctoral researcher, the support of a high school intern, and the development and implementation of a workshop for middle and high school educators.<br/><br/>40Ar/39Ar ages in ice-rafted debris are commonly used to infer the source of these materials, yet interpretations of ice-rafted debris-based data hinge mainly on qualitative approaches. To improve interpretations of these data, this project will develop a geochemical component for MITberg – a dynamic-thermodynamic iceberg model. Model experiments will consist of “tagging” icebergs with new and previously published 40Ar/39Ar data from ice-rafted debris. New 40Ar/39Ar data will be generated from existing sediment cores from the North Atlantic and Nordic Seas as part of this research. By integrating 40Ar/39Ar ice-rafted debris data into iceberg simulations, this project aims to better constrain the origin of ice-rafted debris during Heinrich events – ice sheet destabilization events that occurred in the North Atlantic Ocean every 7,000-12,000 years during the last glacial period (11,7000 to 115,000 years ago). The initiation mechanism underlying these events has remained a mystery despite decades of research. This work not only aims to clarify whether Heinrich events were the product of a single, internal ice sheet mechanism or a multi-ice sheet, basin-wide phenomenon but will provide the template for future polar science research using ice-rafted debris proxy data in other ice sheet contexts. Development of the geochemical ice-rafted debris module will also serve as a steppingstone for a complete source-to-sink ice-rafted debris model, which currently does not exist but is essential for progressing interpretations of these data.<br/><br/>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.
