Modeling buoyancy-driven circulation in an idealized tidewater glacier fjord
Tidewater glacier fjords are narrow, deep inlets connecting marine-terminating glaciers with the continental shelf sea. Over the recent years, the rapid mass loss of the Greenland Ice Sheet has sparked interest in these fjords due to their impacts on submarine glacier melting as well as coastal ocea...
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| Format: | Text |
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2021
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| Online Access: | https://dx.doi.org/10.7282/t3-c8ev-x414 https://rucore.libraries.rutgers.edu/rutgers-lib/66021/ |
| Summary: | Tidewater glacier fjords are narrow, deep inlets connecting marine-terminating glaciers with the continental shelf sea. Over the recent years, the rapid mass loss of the Greenland Ice Sheet has sparked interest in these fjords due to their impacts on submarine glacier melting as well as coastal ocean circulation. In tidewater glacier fjords, subglacial discharge is an important source of buoyancy, which drives the exchange flow and controls salt and heat transports between fjord and the coastal sea. However, due to the difficulty in acquiring field data in the ice-packed environments, direct observations of the oceanographic condition are rare, and the general circulation in these fjords are poorly understood.Numerical model is an alternative approach to explore the buoyancy driven exchange in tidewater glacier fjords. This dissertation uses a coupled ocean/plume model to study the circulation and heat transports in idealized fjord basins and discusses the impacts on submarine melting of the glacier front.Firstly, in order to better represent the subglacial discharge, we developed a new model framework, ROMS-ICEPLUME, to parameterize the rising and initial outflowing stage of the subglacial discharge plume in vicinity of the glacier/ocean boundary. The coupled model is tested for sensitivities over various model configurations and validated with field observations using a quasi-realistic setup. We find that the modeled circulation is very sensitive to the choices of outflow parameterization and coupling method. This model is able to reproduce the strong outflowing plume and its spatial structure observed in a Greenlandic fjord. Results from this part provides an important tool in advancing our understanding of the exchange processes in tidewater glacier fjords.Secondly, using the coupled model framework, the circulation and heat exchange driven by subglacial discharge are simulated in a series of idealized conditions. The buoyancy-driven plume travels along the southside of the fjord channel, and to a great extent resembles the structure of a coastal current. The physical properties of outflowing plume are estimated using model fields and compared with that derived from a shallow water model. We find that the outflow structure is dependent on the location of subglacial river, and plume properties are better predicted by the shallow water model when discharge enters from the southside of the channel. Heat budgets analysis highlights the role of discharge-driven exchange flow in removing submarine melt water from glacier front. This mechanism in theory enhances submarine melting, but it is not well reflected in the modeled melt rates due to limitation of the melting parameterization. |
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