Tracking nutrient and productivity variations over the last deglaciation in the Arctic Ocean

We have reconstructed the surface water environment of the Arctic Ocean ove r the last similar to 50,000 years using measurements of the organic nitrog en and carbon isotope ratios, carbonate and total organic carbon concentrat ions (TOC), and terrestrial biomarkers (lignin and long-chain n-alkanes) in four multicores. Variations in nitrogen isotope ratios that are concordant with TOC and carbonate concentrations (representing foraminifera and exclu ding ice-rafted-debris) reflect differences in relative nutrient utilizatio n of phytoplankton in the surface waters. However, delta N-15 variations al so appear to be dependent on the stratification of the water column and the refore potentially track the exchange of nutrients between deep and surface waters. Low Last Glacial Maximum (LGM) delta N-15 values and higher Holoce ne values are opposite to those recorded in the Southern Ocean. The Arctic Ocean with higher nutrient utilization today compared to the LGM therefore acts as a counterpart to the Southern Ocean, although the global impact on carbon dioxide variations compared to the Southern Ocean is probably low.