In this project, the investigator will examine paleoceanographic records to study how ocean productivity, nutrient cycling, and carbon cycling have been impacted by rapid climate variability. To achieve this aim, the investigator will develop paleoceanographic reconstructions of intermediate water nutrient concentration and provide the first continuous high-resolution (interannual-decadal scale) records of intermediate water biogeochemistry that will extend modern instrumental records. These records will advance our understanding of mechanisms linking rapid variations in atmospheric/surface ocean climate, upwelling, productivity, and deep-sea carbon and nutrient cycling. The investigator will integrate the research into educational activities by establishing a new coral geochemistry research program at a small liberal arts college and support participation of under-represented groups in ocean sciences at both the undergraduate and high-school level.
The impact of climate change on processes such as upwelling, nutrient availability, carbon export and ocean biogeochemistry is currently poorly understood. Paleoceanographic records can provide critical perspective on the mechanisms linking climate, the carbon cycle, and ocean oxygenation in the past. The investigator will use high-resolution (interannual-decadal) geochemical records from deep-sea bamboo corals to reconstruct past changes in nutrient cycling and carbon export for the past 400 years. The study is focused around a central question: How are deep-sea nutrient biogeochemistry and carbon cycling in the California Current System affected by climate change? Trace elemental ratios preserved in bamboo coral skeleton (Ba/Ca) will be used to determine whether changes in surface-ocean-atmospheric climate affect intermediate water mass nutrient cycling on decadal timescales. In particular, this study will closely investigate the last 400 years with a focus on: (1) validating the use of an established intermediate water nutrient proxy in California Current System (CCS) bamboo corals (Ba/Ca), (2) understanding the relationship between intermediate water nutrients and primary productivity in the CCS, and (3) the relationship between CCS export production and rapid climate change in the past (e.g. the Pacific Decadal Oscillation and the El Niño Southern Oscillation). A unique suite of coral archives allows for a depth transect across intermediate waters (792-2055m water depth, in total) and direct comparison with instrumental records.
