The continuing increase in atmospheric carbon dioxide and its potential to affect our climate have made understanding the way carbon moves between different parts of the environment of utmost importance to our society. The ocean holds most of the carbon in our climate system, with the deep ocean naturally containing far higher carbon concentration than the surface due to both biological and physical processes. More carbon in the deep ocean means less in the atmosphere. My research program focuses on the biological and physical processes that send carbon to the deep ocean. The tools I use are high precision measurements of dissolved gases. First, we will make measurements of gases with no biological role (inert gases like neon, argon, krypton, and xenon) to determine how physical processes like temperature change, air-sea gas exchange, and atmospheric pressure affect any gas in the ocean. These measurements will be compared to the predictions of climate models to improve model processes for dissolved gases, including carbon dioxide. Second, we will make measurements of oxygen and its isotopes to determine the rate of ocean productivity (photosynthesis and respiration). These measurements will tell us the efficiency with which ocean ecosystems take up carbon dioxide and send it to the deep ocean in the form of particles. These measurements will also be compared to traditional methods based on incubations of seawater in bottles to understand the differences between methods and the uncertainties in each. Third, we will make measurements of dissolved nitrogen gas to determine the removal of nutrients like nitrate and ammonia from the ocean. The total amounts of nutrients in the ocean (essentially plankton fertilizer) can ultimately control ocean productivity, so we must understand the processes that remove nutrients from the ocean. Together these studies will help us to understand the way that carbon moves through the ocean and to better predict future changes. Better predictions of future ocean and atmospheric carbon dioxide concentrations will benefit Canadians by providing clearer criteria on which government representatives can make decisions regarding energy use and climate change mitigation strategies.