Quantitative Reconstruction of Bottom-Water Nitrate

This technical report presents a quantitative reconstruction of deglacial bottom-water nitrate concentrations in various oxygen-deficient zones of the Pacific Ocean, specifically the Sea of Okhotsk, Gulf of California, Mexican Margin, and Gulf of Guayaquil. The study utilizes the pore density of denitrifying benthic foraminifera as a proxy for nitrate levels. It outlines the observed differences in nitrate concentrations across these sites from the Last Glacial Maximum to the Holocene, attributing variations to factors such as water-column denitrification, water-mass ventilation, primary productivity, and sea surface temperatures. The findings indicate that modern oxygen-deficient zones in the Gulf of Guayaquil and Gulf of California exhibit higher denitrification rates compared to the Last Glacial Maximum, while the Mexican Margin and Sea of Okhotsk show signs of increased oxygen levels. This report contributes to understanding the dynamics of the marine nitrogen cycle and the role of oxygen-deficient zones in global nitrogen cycling.