Tracking Arctic marine productivity across the Holocene - Anthropocene transition using novel compound-specific stable isotope techniques

The overall goal of my research program is to develop, test and apply novel stable isotopic techniques for tracking long-term changes in primary productivity in the Arctic and sub-Arctic Oceans. By the year 2040, Arctic summer sea ice is projected to disappear completely for the first time in perhaps the last 13 million years. It remains unclear if primary productivity will increase or decrease in a future ice-free Arctic. This has urgent global importance for predicting fisheries yields and for mitigation of greenhouse gas emissions via biological sequestration of CO2 to the deep ocean. Loss of ice cover should lead to increases in photosynthetic potential; however, nutrient limitation and loss of habitat for highly productive ice algae could negate any gains in productivity made from longer ice-free growing seasons. Our understanding of physical-biological processes and feedbacks controlling marine productivity are limited by difficulty accessing the remote Arctic environment in all but a narrow window of summer, satellite remote sensors that cannot see deeper than 25 m into the water column, and an acute lack of long-term (multi-decadal) scientific observations. My research program directly addresses these ongoing challenges to scientific progress in two key ways. First, we make use of annual resolution paleo-records contained in the skeletons of deep-sea corals that feed on the sinking flux of recently exported primary productivity. By combining these coral records with those from more traditional sediment cores, paleo-records of unprecedented length and resolution for Arctic waters will be generated. Second, we leverage the breakthrough interpretive potential of carbon and nitrogen stable isotopic analysis of amino acids preserved in corals and sediments. This novel methodology goes beyond traditional bulk isotope methods to provide a means for independently tracking four key processes at the base of marine foodwebs: nutrient source, autotroph community composition, organism trophic position, and microbial degradation. Reconstruction of these variables at annual resolution and over multi-centennial timespans will allow us to test hypotheses on the effect of changing sea ice conditions on nutrient availability and primary productivity. This research builds on a solid track record of innovative and impactful paleo-ecological reconstructions, which are essential for understanding, mitigating and adapting to climate change.