EAGER: Dating Arctic Lake Sediments with Beryllium-10 Markers of Solar Proton Events

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Arctic lake sediment records often have clear layers, called laminations, which form due to the uniqueness of the Arctic seasons. During the short melt season, sediments become mobilized and transported into lakes by streams, where the material is deposited on the lake bottom. This is followed by a lengthy winter characterized by lake surface freezing and the slow settling of fine grained material. Consequently, an annual couplet of sediment, referred to as a varve is formed, with coarser material underlying a fine-grained clay cap. These varved records offer valuable information about past climate and environmental changes. However, it is crucial to confirm their timeline using an independent method to ensure confidence in the established time scale. Solar Proton Events (SPEs) are one such potential independent method. SPEs are bursts of high-energy particles released from the Sun during specific solar activities. When these particles reach Earth, they can interact with atmospheric gases, creating isotopes like 10Be, which make their way onto the land surface and eventually into lake sediments. This study proposes to use 10Be anomalies from SPEs as a tool for verifying varve records. By analyzing and comparing 10Be concentrations in laminated sediments collected from various locations across the sub- to high-Arctic, this research aims to determine if 10Be increases associated with SPEs can be used as a reliable method for confirming varved record chronologies. If this method is confirmed, demonstrating that sediment 10Be increases associated with SPEs can verify varve records, it would be a transformative development, allowing precise comparisons between different varved lake sedimentary records and various other records like ice cores, tree rings, and lacustrine (lake-related) records. Ultimately, this could significantly improve our understanding of past climate changes and variability. The research plan includes STEM opportunities for high school students to learn about climate change and to better understand their local environment. This will involve an active learning workshop. The project will also involve students from the University’s Honors College (Commonwealth College) who will participate in lab work and gain research experience.As a consequence of the short Arctic melt season, when sediment is mobilized and then carried by streams and deposited in lakes, followed by a long period when the surface is frozen and fine-grained material settles to the sediment surface, many Arctic lake sediment records are well-laminated, with an annual couplet of sediment (a varve); a layer of coarse material overlain by a fine-grained clay cap. These laminated layers have the potential to serve as a paleo-clock (a chronology). However, to provide confidence in this clock, it needs to be confirmed by an independent method. This study focuses on such a confirmation. The investigator proposes to identify 10Be anomalies resulting from solar proton events (SPEs) in a set of laminated sediments collected from lakes in different locations, ranging from the sub- to high Arctic, to test whether 10Be increases associated with SPEs can be used to confirm varved record chronology. If successful, this work would represent a transformative development, allowing high-resolution comparisons to be made between different varved lake sedimentary records and between ice cores, tree rings, and lake sediments. The research plan includes STEM opportunities for high school students to learn about climate change and to better understand their local environment. This will involve an active learning workshop. The project will also involve students from the University’s Honors College (Commonwealth College) who will participate in lab work and gain research experience.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.