Advanced Radiocarbon Dating and Molecular-Level Tools for Evaluating Marine Carbon Cycling in the Canadian Arctic

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The marine carbon cycle plays an important role in regulating Earth's climate on timescales of years to millennia. The Canadian Arctic is warming at nearly double the rate as the rest of the planet, and as a result, Arctic seas will undergo unprecedented change in coming decades. These changes include: increased water temperatures, acidification and hypoxia that directly affect how ecosystems function. Marine carbon takes many forms, from large particulate detritus to small dissolved organic carbon (DOC) molecules and dissolved inorganic carbon salts (DIC; primarily as bicarbonate). This proposal aims to address fundamental knowledge gaps in our understanding of the Canadian Arctic marine carbon cycle. The proposed research will couple advanced stable carbon (13C) and radiocarbon (14C) isotopic measurements together with dissolved microbial biomarker analysis and nuclear magnetic resonance spectroscopy in order to quantify carbon sources, transformations and cycling rates within three Canadian Arctic regions: Baffin Bay, the Canadian Archipelago and Hudson Bay/Foxe Basin. The core research questions are: (1) What are the distributions and 14C-ages of marine DIC and DOC in the Canadian Arctic? (2) What are the residence times and ventilation ages of Canadian Arctic water masses? (3) What are the main sources of carbon persisting in these regions? and (4) to what extent does DOC biomolecular and chemical composition ultimately determine its biological availability to heterotrophic bacteria and its long-term persistence (i.e. 14C-age) in Arctic waters? These questions will be examined in field and lab-based studies conducted by 4 MSc students, 3 PhD students and 6-8 undergraduate students, recruited and trained using approaches designed to maximize equity, diversity and inclusion. Our results will advance our understanding of marine carbon cycling dynamics within the Canadian Arctic and improve our ability to predict carbon stocks and fluxes. This work will also help advance our ability to parametrize and incorporate DOC biogeochemical cycling into future Arctic Earth System Models. The research will take advantage of new and existing collaborations with world-renowned researchers within Canada and abroad. This research will integrate the use of two National Research Facilities, the André E. Lalonde Accelerator Mass Spectrometry Laboratory and Amundsen Science - further building Canada's profile as a leader in carbon cycle research in a period of rapid Arctic climate change. I have played a leading role in developing and improving marine 14C methods that have helped us quantify rates of organic carbon cycling in the ocean. My interdisciplinary background in the fields of chemical oceanography, isotope geochemistry, and accelerator mass spectrometry make me uniquely qualified to lead the proposed research program.