Graduate Thesis Or Dissertation
 

Estimating Drag and Roughness along a Near-Vertical Ice-Ocean Boundary on a Grounded Iceberg

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/zg64tv18v

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  • Ice–ocean interactions have profound consequences for the ocean and climate, influencing the rate of sea level rise. Submarine melt is commonly parameterized using a three-equation formulation for the heat, salt, and momentum conservation equations coupled to a buoyant plume model, together called plume-melt theory. However, recent direct observations of terminus retreat at a tidewater glacier indicate that the plume-melt theory approach to predicting submarine ice melt underestimates the actual melt rate at the ice face by more than an order of magnitude. This suggests that there are important yet missing parameterizations of physical processes in plume-melt theory for predicting glacier melt rates. One of these potential gaps may be the use of an empirically derived drag coefficient from measurements collected beneath sea-ice to estimate melt at tidewater glacier termini. Drag coefficients under sea-ice are likely very different than at a near-vertical ice face due to the differing influence of buoyancy. Moreover, direct observations of submarine ice morphologies are extremely limited, leaving the impact of shape and roughness characteristics on the drag coefficient uncertain. We present an approach for estimating the drag coefficient that accounts for the influence of both the external circulation conditions and local flow due to buoyancy production from ice melt. Iceberg keel depth, shape, roughness, and melt were measured at a grounded iceberg in LeConte Bay, AK using a multibeam sonar. Remotely operated vehicles (ROVs) equipped with an Acoustic Doppler Current Profiler (ADCP), and temperature and salinity sensors were used to measure mean flow conditions and boundary layer structure at different depths along the iceberg. Estimates of the drag coefficient were made at a near-vertical ice-ocean boundary using the aforementioned unique observations of high-resolution iceberg geometries and mean flow conditions within 2 meters of the ice face. These estimates, which take into account the ice shape and roughness characteristics and the effect of buoyancy production, will be used to better parameterize models of melt.
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