Understanding ocean carbon uptake mechanisms during glacial-interglacial cycles

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Ever since scientists first discovered that carbon dioxide levels were low during ice ages, they have been proposing theories to understand why. Many studies have examined the role of individual mechanisms in sequestering carbon dioxide in the ocean, and others have closely examined how carbon dioxide exits the ocean at the end of an ice age. As Earth system models have yet to simulate carbon dioxide changes over a full glacial-interglacial cycle, it becomes increasingly important to bring together new data, both to quantify environmental changes of the ocean, as well as to evaluate how well models can identify the most important mechanisms in glacial climate change. My research program focuses on the fate of the ocean as the Earth enters an ice age, and how different feedbacks play dominant roles during different stages of a glacial cycle. My long-term objective is to bring together multiple lines of paleo-oceanographic evidence to create a more complete picture of how the ocean changes as the Earth enters a glacial cycle, and to use this synthesis to test which oceanographic processes are the most important contributors to the sequestration of atmospheric carbon dioxide. The three projects in my research program are designed to reconstruct different aspects of ocean physics and biogeochemistry during different stages of a glacial period; these aspects include dust deposition, ocean productivity, sea ice cover, and deep-ocean temperatures. My approach will combine global environmental data compilation - to provide novel and innovative spatial and temporal comparisons of multiple lines of data - with new analyses on marine sediment samples - to fill existing gaps in knowledge about how the ocean is changing. The projects will provide important interdisciplinary training to two doctoral, one Masters, and five undergraduate students. One key outcome of this research is that it will provide multiple benchmark datasets of changes in ocean temperature, marine productivity, dust deposition, and Southern Ocean sea-ice cover, with explicit focus on the early- and mid-glacial time periods that have not previously been studied. These data will benefit climate modelers who wish to evaluate the skill of Earth system models, such as Canada's UVic Earth System Model, in simulating carbon-climate feedbacks during past time periods when the Earth experienced different boundary conditions. Furthermore, when brought together, these projects will provide a comprehensive test of hypotheses examining how the ocean circulation changes during large-scale climate fluctuations are linked with changes in sea ice cover, iron fertilization from dust, marine productivity, and ocean carbon sequestration.