Sources of N₂O in Past Ocean Ecosystems

The balance of the nitrogen cycle in the present ocean and over glacial/interglacial timescales is a question of great interest. As nitrogen can be a limiting nutrient to ocean primary productivity and export production, changes in the supply of nitrogen may impact climate through altering the biological drawdown of CO₂. There is strong evidence for changes in the rate of denitrification in the three main oxygen minimum zones on glacial/interglacial timescales, with characteristically lower denitrification rates during glacial periods. The concentrations of N₂O in the atmosphere also are lower during glacial periods than during intervening warm periods. I am interested in exploring a possible connection between the strength of marine denitrification and N₂O concentrations/isotopic signatures in the atmosphere. Using concentrations and stable isotope signatures of N₂O trapped in ice cores, we may be able to add an additional constraint on the strength of water column denitrification and/or surface nitrification (driven by productivity) during glacial/interglacial periods and transitions.

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