Collaborative Research: Elucidating the Ocean Dynamics Governing Melt at Glaciers Using Lagrangian Floats

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The proposed study will determine the physical processes that cause melting at an Alaskan glacier that ends in a fjord. The study will try to prove whether recirculating cells and waves below the sea-surface cause stronger velocities than the flows associated with melting glaciers. The project will develop instruments that drift in three dimensions, capable of drifting along a fixed depth or move with a water type. These drifting instruments will be combined with instrumentation that is fixed at one place and with ship measurements, and with computer models to decipher the interactions of different three-dimensional motions at the glacier face; and to resolve the time and space structure of flows that enhance heat flux to, and melting of, the glacier. Understanding of these processes shall allow projections of glacier mass loss and resulting melt-water flux into the polar oceans. As Broader Impacts, the study will help in global-scale formulations of submarine glacial melting. The Principal Investigator is an early career investigator, as well as two of the Co-PIs. The project will support a couple of graduate students.The proposed work will characterize the processes that drive near-glacier circulation and submarine glacial melt at LeConte Glacier, Alaska. The hypothesis is that accelerated glacier melting results from different-scale recirculations and internal waves at the glacier face that are not included in standard ocean-model parameterizations of glacial melt; and that these recirculations and internal wave motions overwhelm the plume velocities. The hypothesis will be tested via development of microfloats (µfloats) that drift in 3D, capable of drifting along a fixed depth or move with water (an isopycnal surface). The study will use acoustically tracked Lagrangian µfloats, mooring and vessel observations, and numerical modeling to elucidate the interplay of: (1) entrainment and recirculation driven by discharge plumes; (2) internal waves and their contributions to vertical velocity at the glacier face; and (3) the spatiotemporal structure of lateral circulations believed to enhance heat flux to the glacier. These processes shall allow projections of glacier mass loss and resulting melt-water flux into the polar oceans. High-resolution numerical simulations will inform deployments and be used to synthesize results. As Broader Impacts, the study will inform parametrizations of submarine melting. The PI and two Co-PIs are early career investigators, and the project will support a couple of graduate students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.