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• 1. [Article] Distributed fiber-optic temperature sensing for hydrologic systems

  This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://www.agu.org/.

  Citation × Citation Citation Abstract Copy Title: Distributed fiber-optic temperature sensing for hydrologic systems Author: van de Giesen, Nick, Stejskal, Martin, Westhoff, Martijn, Huwald, Hendrik, Mallet, Alfred, Luxemburg, Wim, Zeman, Josef, Parlange, Marc B., Thevenaz, Luc, Selker, John S. This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://www.agu.org/. Title: Distributed fiber-optic temperature sensing for hydrologic systems Author: van de Giesen, Nick, Stejskal, Martin, Westhoff, Martijn, Huwald, Hendrik, Mallet, Alfred, Luxemburg, Wim, Zeman, Josef, Parlange, Marc B., Thevenaz, Luc, Selker, John S. This is the publisher’s final pdf. The published article is copyrighted by American Geophysical Union and can be found at: http://www.agu.org/. Close

• 2. [Article] Using reanalysis data to characterize Arctic and Sub-Arctic glaciers

  The net mass balance fluctuations of Arctic and Sub-Arctic glaciers, north of 47.5° North latitude, are described over a 45-year period from 1957 to 2002 using two parameters derived from a gridded climatology ...

  Citation × Citation Citation Abstract Copy Title: Using reanalysis data to characterize Arctic and Sub-Arctic glaciers Author: Ourada, Quin The net mass balance fluctuations of Arctic and Sub-Arctic glaciers, north of 47.5° North latitude, are described over a 45-year period from 1957 to 2002 using two parameters derived from a gridded climatology reanalysis. Variability among 185 measured glaciers was represented according to two main components. The first component represents the temporal variability of the net balance series derived from a statistically defined geographic region. The second component represents the glacier-specific variability in the net balance series (the amplitude of variability). Each component was numerically derived using gridded monthly mean temperature and precipitation data at a 2.5° spatial resolution. These two main components of the net balance series can be determined from simple glacier location data. The temporal variability component was determined using patterns of warm season temperature that were then used to define the statistically correlated regions. The glacier-specific component was approximated along continuum of continentality. Continentality was based on the relative ratio of warm to cool season temperature at the glacier location, which was then normalized and differenced using precipitation magnitude. Ultimately 21 distinct geographic regions containing at least one representative glacier were defined for the first, temporal component. In data-rich regions, such as the Alps and Scandinavia, spatial variability was identified on a finer scale than individual mountain ranges. The temporal evolution of measured net balance series within each region were more closely related to each other than measured mass balance on the scale of mountain ranges. This temporal signal can be considered the most likely temporal signal that would be characteristic of unmeasured glaciers within the spatial extent of the region. This spatial extent defined for each region is specific, and based on similarities in physical climatology as opposed to more vaguely defined regions based on mountain ranges or other geographic features. The, second, glacier specific component of the series was related to net balance standard deviations (58% variance explained), balance amplitude (55% variance explained) and climate sensitivity (56% variance of temperature sensitivity and 52% variance of precipitation sensitivity explained) for measured glaciers. The normalization process resulted in a glacier continuum ranging from -1 to 1 to describe the relative position of a glacier along a continuum or wet-maritime to dry continental. These two pieces of information can be used together to approximate a large component of the net balance series for an unmeasured glacier based on location alone. Representing unmeasured glaciers in this manner is, by no means, a substitute for actual field measurements or complex and highly parameterized mass balance models. This approach is also limited in accuracy by the spatial resolution of the gridded climatologies used, which at this time are still quite coarse, 2.5°. However, in lieu of more detailed data, a simple approximation of glacier mass balance can be made and those measured glaciers most likely to exhibit similar characteristics can be identified to assist in tuning parameters for a more detailed mass balance model. Title: Using reanalysis data to characterize Arctic and Sub-Arctic glaciers Author: Ourada, Quin The net mass balance fluctuations of Arctic and Sub-Arctic glaciers, north of 47.5° North latitude, are described over a 45-year period from 1957 to 2002 using two parameters derived from a gridded climatology reanalysis. Variability among 185 measured glaciers was represented according to two main components. The first component represents the temporal variability of the net balance series derived from a statistically defined geographic region. The second component represents the glacier-specific variability in the net balance series (the amplitude of variability). Each component was numerically derived using gridded monthly mean temperature and precipitation data at a 2.5° spatial resolution. These two main components of the net balance series can be determined from simple glacier location data. The temporal variability component was determined using patterns of warm season temperature that were then used to define the statistically correlated regions. The glacier-specific component was approximated along continuum of continentality. Continentality was based on the relative ratio of warm to cool season temperature at the glacier location, which was then normalized and differenced using precipitation magnitude. Ultimately 21 distinct geographic regions containing at least one representative glacier were defined for the first, temporal component. In data-rich regions, such as the Alps and Scandinavia, spatial variability was identified on a finer scale than individual mountain ranges. The temporal evolution of measured net balance series within each region were more closely related to each other than measured mass balance on the scale of mountain ranges. This temporal signal can be considered the most likely temporal signal that would be characteristic of unmeasured glaciers within the spatial extent of the region. This spatial extent defined for each region is specific, and based on similarities in physical climatology as opposed to more vaguely defined regions based on mountain ranges or other geographic features. The, second, glacier specific component of the series was related to net balance standard deviations (58% variance explained), balance amplitude (55% variance explained) and climate sensitivity (56% variance of temperature sensitivity and 52% variance of precipitation sensitivity explained) for measured glaciers. The normalization process resulted in a glacier continuum ranging from -1 to 1 to describe the relative position of a glacier along a continuum or wet-maritime to dry continental. These two pieces of information can be used together to approximate a large component of the net balance series for an unmeasured glacier based on location alone. Representing unmeasured glaciers in this manner is, by no means, a substitute for actual field measurements or complex and highly parameterized mass balance models. This approach is also limited in accuracy by the spatial resolution of the gridded climatologies used, which at this time are still quite coarse, 2.5°. However, in lieu of more detailed data, a simple approximation of glacier mass balance can be made and those measured glaciers most likely to exhibit similar characteristics can be identified to assist in tuning parameters for a more detailed mass balance model. Close

• 3. [Article] Modeling Circulation Dynamics and Submarine Melt in Greenland Fjords

  Meltwater accumulated on the Greenland Ice Sheet drains to glacier beds, discharging into fjords hundreds of meters below sea level. The injection of meltwater at depth generates an upwelling plume that ...

  Citation × Citation Citation Abstract Copy Title: Modeling Circulation Dynamics and Submarine Melt in Greenland Fjords Author: Carroll, Dustin Year: 2017 Meltwater accumulated on the Greenland Ice Sheet drains to glacier beds, discharging into fjords hundreds of meters below sea level. The injection of meltwater at depth generates an upwelling plume that entrains warm ocean water as it rises along the terminus, increasing submarine melt and driving a fjord-scale exchange flow. However, due to sparse ocean-glacier observations, we lack a process understanding of how plumes control fjord circulation and submarine melt. Combining numerical modeling, theory, and observations, this dissertation investigates near-glacier plume dynamics, the influence of glacier depth on plume structure and submarine melt, and the role of fjord-glacier geometry on circulation in tidewater glacier fjords. In Chapter II, I use buoyant plume theory and a nonhydrostatic, three-dimensional ocean–ice model to investigate the sensitivity of plume dynamics to subglacial discharge, turbulent diffusivity, and conduit geometry. Large discharges result in plumes with positive temperature and salinity anomalies in the upper water column. Fjord circulation is sensitive to conduit geometry; distributed subglacial discharge results in a stronger return flow of warm water toward the terminus. In Chapter III, I use buoyant plume theory, initialized with realistic ranges of subglacial discharge, glacier depth, and ocean stratification, to investigate how plume structure and submarine melt vary during summer months in 12 Greenland fjords. Grounding line depth is a primary control on plume-induced submarine melt: deep glaciers produce warm, salty subsurface plumes that undercut termini, and shallow glaciers produce cold, fresh surface-confined plumes that can overcut. Finally, in Chapter IV, I use regional-scale numerical ocean simulations to systematically evaluate how fjord circulation forced by subglacial plumes, tides, and wind stress depends on fjord width, glacier depth, and sill height. Glaciers grounded below sill depth can draw shelf waters over a shallow sill and into fjord basins with seasonal subglacial discharge; this process is independent of external shelf forcing. These results underscore the first-order effect that subglacial discharge and fjord-glacier geometry have in controlling fjord circulation and, thus, ocean heat flux to the ice. This dissertation includes previously published and co-authored material. Title: Modeling Circulation Dynamics and Submarine Melt in Greenland Fjords Author: Carroll, Dustin Year: 2017 Meltwater accumulated on the Greenland Ice Sheet drains to glacier beds, discharging into fjords hundreds of meters below sea level. The injection of meltwater at depth generates an upwelling plume that entrains warm ocean water as it rises along the terminus, increasing submarine melt and driving a fjord-scale exchange flow. However, due to sparse ocean-glacier observations, we lack a process understanding of how plumes control fjord circulation and submarine melt. Combining numerical modeling, theory, and observations, this dissertation investigates near-glacier plume dynamics, the influence of glacier depth on plume structure and submarine melt, and the role of fjord-glacier geometry on circulation in tidewater glacier fjords. In Chapter II, I use buoyant plume theory and a nonhydrostatic, three-dimensional ocean–ice model to investigate the sensitivity of plume dynamics to subglacial discharge, turbulent diffusivity, and conduit geometry. Large discharges result in plumes with positive temperature and salinity anomalies in the upper water column. Fjord circulation is sensitive to conduit geometry; distributed subglacial discharge results in a stronger return flow of warm water toward the terminus. In Chapter III, I use buoyant plume theory, initialized with realistic ranges of subglacial discharge, glacier depth, and ocean stratification, to investigate how plume structure and submarine melt vary during summer months in 12 Greenland fjords. Grounding line depth is a primary control on plume-induced submarine melt: deep glaciers produce warm, salty subsurface plumes that undercut termini, and shallow glaciers produce cold, fresh surface-confined plumes that can overcut. Finally, in Chapter IV, I use regional-scale numerical ocean simulations to systematically evaluate how fjord circulation forced by subglacial plumes, tides, and wind stress depends on fjord width, glacier depth, and sill height. Glaciers grounded below sill depth can draw shelf waters over a shallow sill and into fjord basins with seasonal subglacial discharge; this process is independent of external shelf forcing. These results underscore the first-order effect that subglacial discharge and fjord-glacier geometry have in controlling fjord circulation and, thus, ocean heat flux to the ice. This dissertation includes previously published and co-authored material. Close