Dynamics of Greenland’s glacial fjords
Citable URI
https://hdl.handle.net/1912/7965Location
GreenlandDOI
10.1575/1912/7965Abstract
Glacial fjords form conduits between glaciers of the Greenland Ice Sheet and the North Atlantic.
They are the gateways for importing oceanic heat to melt ice and for exporting meltwater into the
ocean. Submarine melting in fjords has been implicated as a driver of recent glacier acceleration;
however, there are no direct measurements of this melting, and little is known about the fjord
processes that modulate melt rates. Combining observations, theory, and modeling, this thesis
investigates the circulation, heat transport, and meltwater export in glacial fjords.
While most recent studies focus on glacial buoyancy forcing, there are other drivers – e.g. tides,
local wind, shelf variability – that can be important for fjord circulation. Using moored records from
two major Greenlandic fjords, shelf forcing (from shelf density fluctuations) is found to dominate the
fjord circulation, driving rapid exchange with the shelf and large heat content variability near the
glacier. Contrary to the conventional paradigm, these flows mask any glacier-driven circulation in
the non-summer months. During the summer, when shelf forcing is reduced and freshwater forcing
peaks, a mean exchange flow transports warm Atlantic-origin water towards the glacier and exports
glacial meltwater.
Many recent studies have inferred submarine melt rates from oceanic heat transport, but the
fjord budgets that underlie this method have been overlooked. Building on estuarine studies of salt
fluxes, this thesis presents a new framework for assessing glacial fjord budgets and revised equations
for inferring meltwater fluxes. Two different seasonal regimes are found in the heat/salt budgets for
Sermilik Fjord, and the results provide the first time-series of submarine meltwater and subglacial
discharge fluxes into a glacial fjord.
Finally, building on the observations, ROMS numerical simulations and two analytical models
are used to investigate the dynamics of shelf-driven flows and their importance relative to local
wind forcing across the parameter space of Greenland’s fjords. The fjord response is found to
vary primarily with the width relative to the deformation radius and the fjord adjustment timescale
relative to the forcing timescale. Understanding these modes of circulation is a step towards accurate
modeling of ocean-glacier interactions.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2016
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Suggested Citation
Thesis: Jackson, Rebecca H., "Dynamics of Greenland’s glacial fjords", 2016-06, DOI:10.1575/1912/7965, https://hdl.handle.net/1912/7965Related items
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