Quantifying the Ocean's Carbon Pumps with Dissolved Gas Measurements

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The ocean naturally removes carbon dioxide from the atmosphere, transports it to the deep, and stores it there, resulting in lower atmospheric levels and a more moderate climate. As humans burn fuels and add carbon dioxide to the atmosphere, we need to understand how the ocean's natural carbon transport mechanisms work, how fast they work, and how they are changing in order to make accurate projections of future climate that our society can use to make decisions. My research seeks to uncover and quantify these mechanisms using novel measurements of dissolved gases.******Our research group has developed methods to make high precision measurements of dissolved noble gas concentrations (neon, argon, krypton, and xenon). These gases have no biological function, responding only to physical processes in the ocean. We will use our noble gas measurements to quantify the rates of physical processes that impact all gases in the ocean, such as air-sea gas exchange and temperature-driven solubility changes. These processes control how much carbon is carried as dense waters sink into the deep sea. Through direct collaborations with large-scale climate modellers, we will improve the way these processes are represented in the models from which climate projections are made.******Our research also focuses on biological processes, particularly the sinking of organic carbon created by photosynthesis out of the surface ocean, an important but poorly quantified carbon transport mechanism. We have developed ways of quantifying this “export” rate from the surface using high precision measurements of the oxygen/argon ratio of dissolved gases. We will now expand our techniques to quantify carbon export from sensors that detect oxygen concentrations on ocean floats and gliders that autonomously move up and down through the water column. This work will expand the space and time scales over which these estimates are made. One of our overall goals is to establish a baseline against which future changes in ocean productivity can be detected. Any changes could affect not only ocean uptake of atmospheric carbon dioxide but also the ocean ecosystem and fisheries that rely on it.******Our third research focus is on reactions that strip bioavailable nitrogen, which plants need to photosynthesize, out of the ocean. These reactions, known as denitrification, take place in regions of the ocean with no oxygen. These oxygen deficient zones are expanding, which means that denitrification could affect global rates of ocean biological productivity in the future. We have developed methods to detect this reaction using high precision measurements of N2 gas dissolved in the ocean. We will quantify denitrification both in local Saanich Inlet, which provides an accessible natural laboratory to study oxygen deficient zones, and in the Arctic Ocean, where these reactions are least well quantified.