Grant: Discovery Grants Program - Individual

Permafrost, the perennially frozen ground spanning the Arctic, stores large stocks of `old' and labile organic carbon (OC). Sharply rising circum-Arctic temperatures accelerate the thaw of this vulnerable OC pool, making it accessible to remineralization and erosion. Upon remineralization, the previously freeze-locked OC is emitted to the atmosphere as carbon dioxide or methane and causes a feedback mechanism that further amplifies the greenhouse effect, warming, and permafrost thaw. Erosion/mobilization of permafrost OC into aquatic settings, such as rivers and coastal oceans, leads to additional OC remineralization but also burial and sequestration in sediments. Re-buried permafrost represents an archive of past permafrost dynamics beyond observational records, which allows assessing the sensitivity and response of permafrost OC to natural climatic as well as anthropogenic forcing. This information is critical to predict the future response of permafrost to climate change, which has already had profound effects for Arctic ecosystem functions, infrastructure and economies, and the livelihood of local communities. This research program will exploit the source specificity of biomarker molecules and the qualitative information carried by their radiocarbon (14C) isotopic composition to quantify past and present permafrost OC fluxes to the Canadian Arctic Ocean in response to natural climatic and anthropogenic forcing. Marine sediments, permafrost field samples, and laboratory-based microcosm experiments will be used on different spatial and temporal scales to determine the quantity and quality of permafrost OC released following warming-induced permafrost thaw and the associated atmospheric and oceanic feedbacks. Climate analogs such as the last deglacial and the Industrial Age will be compared using marine sediment records that capture permafrost release during meltwater events (Hudson Strait and St. Lawrence) or permafrost release during the last millennium (Hudson Bay). Moreover, this program will assess permafrost type-specific vulnerabilities (continuous, discontinuous, and sporadic), employ a novel integrated isoscape approach to gain a holistic understanding of changing molecular permafrost dynamics, and investigate feedbacks to the ocean carbonate system. The program will train a total of 9HQP (4 PhD students and 5 undergraduate summer students) within the next 5 years. Using state-of-the-art molecular tools new to the Canadian research environment, the data obtained through this program will fill a critical need in the past circum-Canadian/circum-Arctic permafrost budget and are crucial for climate models predicting future changes. This program will furthermore help solve a conundrum in the global carbon cycle by delivering unprecedented insight into the molecular isotopic heterogeneity of terrestrial OC on land, during transfer into and alteration/priming in the ocean, and burial in sediments.