OCE-RIG: Refining a Diatom-Based Sea Ice Proxy for the Bering Sea Using Water, Ice and Sediment Samples to Improve the Robustness of Sea Ice Reconstructions

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As summer sea ice disappears from the Arctic, we strive to know if this has happened in the past and if so, how often. Unfortunately, satellites have only been tracking sea ice since 1979. In order to determine natural fluctuations in sea ice, we need a much longer record. Sediments deposited below sea ice can extend the record of sea ice by thousands to hundreds of thousands of years. This project builds on work to develop a proxy for sea ice by looking at the relationship between diatoms (algae) found in sea ice and in the sediments below. This project will additionally attempt to increase and diversify participation in the ocean sciences by introducing a group of high-achieving, under-represented students from Iowa to the excitement of sea-ice research. The investigator and students will spend a week collecting an ice core from a frozen lake and analyzing it. The students will get to experience fieldwork and will connect research done in remote, exotic locations to the their own backyards.Although long-term goals of the investigator are to put modern changes in the Bering Sea in the context of the geological record, the specific goals of this project are to:1. Determine the spatial patterns of diatoms living in sea ice and sea water across the Bering Sea Shelf in spring 2006 and 2007.2. Determine the seasonal succession of diatoms living in sea ice and open water over the Chukchi Sea Shelf from summer 2015 to summer 2016.The investigator will examine diatom assemblages in a collection of seawater, sea ice, and sediment trap samples and then compare these assemblages to those in the top 1 cm of sediments below. Seawater and sea ice samples were collected in 2006 and 2007, while the sediment trap samples will come from the Chukchi Ecosystem Mooring which will begin collecting a full annual cycle of diatom sedimentation this summer. The investigator will count cleaned diatoms at 1000x magnification using standard counting methods and taxonomy, identifying to the species level whenever possible. The driving hypothesis of the research is that a predictable subset of diatoms is in the ice algal and spring blooms and is also in the sediments directly below. The investigator also aims to test the long-held hypothesis that sea ice diatoms are preferentially dissolved at the sea surface. A robust sea ice proxy is essential for realistically reconstructing past sea ice extent and retreat in the Arctic Ocean. This work will serve to ground statistically based sea ice proxy in ecological reality. This pilot study, awarded to a new researcher at Iowa State who is in the process of establishing her lab, will be leveraged to launch a larger, sea-based study that will include deploying sediment traps in the Bering Sea. Research results will enable climate modelers to use records of sea ice during previous warmings to predict how primary productivity and sea ice will change in the coming decades and to anticipate the ecosystem-scale impacts such changes may precipitate.