Grant: Discovery Grants Program - Individual

The retreat of the Laurentide Ice Sheet (LIS) across Canada played an important role in the climate variability of the last deglaciation and onset of the Holocene (our current interglacial period) through large discharges of ice and meltwater that disturbed the Atlantic Meridional Overturning Circulation (AMOC) - a major system that regulates Earth's climate. These freshwater forcing mechanisms are now under scrutiny due to the current sustained melting of the Greenland Ice Sheet and the attendant freshening of the North Atlantic, which may lead to a slowing of AMOC and cause significant climate feedbacks. Although paleoclimate data may provide insight on long-term AMOC variability, the impact of former freshwater forcings is still debated, as the source, timing and magnitude of meltwater fluxes remain poorly documented by geological archives - a situation that reflects uncertainties on some aspects of the deglaciation. The Labrador ice Dome (LiD) that covered eastern Canada was one of the main components of the LIS. Broad reconstructions indicate that the late deglaciation stages took place in northern Quebec, where ice withdrawal caused the bulk of meltwater produced by the LiD decay and drainage of ice-dammed lakes to be routed eastward to Ungava Bay near the Labrador Sea - a sensitive component of AMOC. However, assessing the impact of the LiD retreat on the ocean during the early Holocene is prevented by the lack of constraints on the timing of ice margin positions and pattern of ice withdrawal, which modulated meltwater fluxes to the ocean. The proposed Discovery Grant Program is built around two long-term objectives: 1) develop a comprehensive framework for the late LiD deglaciation that will provide detailed constraints on the pattern of ice retreat and configuration of glacial lakes; and 2) produce new geochronological data that will yield ice-margin histories and allow robust estimates of ice sheet retreat rates and timing of meltwater discharges. To meet these goals, strategic features of the geomorphological and sediment records of northern Quebec will be studied through a field-based approach combining detailed landscape analyses and novel applications of Terrestrial Cosmogenic Nuclide dating on deglacial landforms. This research will yield much-needed datasets detailing temporal changes in areal extent of the LiD, which will improve paleogeographic reconstruction accuracy and provide critical data for several fields of fundamental and applied sciences like Quaternary geology, archeology, or mineral exploration in glaciated terrains. Results will also yield reliable assessments of the LiD decay rates and attendant freshwater input to the Labrador Sea during a period of rapid warming. Together, the different results will refine boundary conditions that are critically required by paleo/predictive climate models to fully assess the impact of the ongoing cryospheric and hydrological changes taking place around the North Atlantic today.