Thesis (M.S.)--Humboldt State University, 2009. / Includes bibliographical references (leaves 39-45). Also available via Humboldt Digital Scholar.

Terrestrial glacial geomorphology has long been used to evaluate the extent, chronology and dynamics of former glaciers and ice sheets. New marine geophysical methods provide an opportunity to study the glacial submarine morphology of modern continental shelves and fjord systems. This makes it possible to study landform assemblages in the submarine settings that are often better preserved than their terrestrial counterparts. This study focuses mainly on the recent surge history of the tidewater glacier Tunabreen, which calves into Tempelfjorden in Western Spitsbergen. Tunabreen is a small outlet glacier of the Lomonosovfonna ice cap and has experienced severalsurges and terminal retreats during the last century. The multiple surge events havemost likely removed or reworked landform assemblages created by earlier surges,resulting in a complex geomorphological imprint on the bed of Tempelfjorden. Tunabreen has left a specific morphological imprint on the sea floor, consisting of iceflow‐parallel lineations and generally flow‐transverse retreat moraines. Comparisonof retreat moraines mapped from high resolution multibeam bathymetric data andglacier terminal positions, established using remote sensing imagery suggest that themoraines in the inner part of Tempelfjorden are annually formed recessionalmoraines, formed during winter still stands of the glacier margin or during its minorreadvances. Although detailed reconstruction of glacier surge dynamics based solelyon the landform distribution is challenging, it is evident that Tunabreen hasexperienced fast flow during surges and semiannual retreat of the margin after thesurges. The main achievements of this study are a spatial reconstruction of the dynamics ofTunabreen, which has experienced three surges during the last hundred years.Together with the Little Ice Age surge of the adjacent von Postbreen, four recentsurges have been recorded in Tempelfjorden since 1870, which distinguishes thestudy area from earlier studied Svalbard tidewater surge glacier settigs, where theglaciers have been known to surge only once or twice. However a detailedunderstanding of surge triggering mechanisms and their role in controlling thedynamics of the tidewater glaciers in Svalbard is still poor and requires furtherinvestigations. Svalbard, where most of the small outlet glaciers are believed to be ofsurge type, is an excellent natural laboratory for such investigations.

No description available.

Tidewater glaciers form a significant drainage catchment of glacierised areas, directly transporting meltwater from the terrestrial to the marine environment. Surface melt of glaciers in the Arctic is increasing in response to warmer atmospheric temperatures, whilst tidewater glaciers are also exposed to warmer ocean temperatures, stimulating submarine melt. Increased freshwater discharge not only freshens fjord waters, but also plays a key role in glacimarine sedimentary processes, transporting sediment to glacial fjords. Despite this, the temporal evolution of meltwater production, storage and release from tidewater glacier systems at seasonal and interannual time scales is poorly understood. This leaves large uncertainties in the predictions for future sea level rise, ocean circulation and the impacts on the marine ecosystem. This study focuses on Kronebreen, a tidewater glacier which flows into the head of Kongsfjorden, north west Svalbard. Surface melt produces freshwater runoff, which is discharged from the grounding line as a buoyant, sediment laden plume, which spreads laterally across the surface water. This supraglacial melt is the dominant freshwater source, contributing an order of magnitude more freshwater to Kongsfjorden, than direct submarine melting of the ice face. Calibration of MODIS band 1 satellite imagery with in situ measurements of Total Suspended Solids and spectral reflectance, provides a method to quantify meltwater and sediment discharge. Plume extent has been determined for each cloud free day, from June to September, 2002 - 2013. Analysis of plume extent with atmospheric temperature and modeled surface runoff, gives a source to sea insight to meltwater production, storage and discharge. The extent of the plume changes in response to meltwater; larger plumes form when discharge increases. These results reveal that meltwater discharge into Kongsfjorden lags atmospheric temperature, the primary driver of meltwater production, by over a week during June and July. This is reduced to only 1 - 2 days in August and September, indicating a decline in meltwater storage as the ablation season progresses, and the development of more efficient glacial drainage. Sediment plumes respond to meltwater production, making them a valuable tool for quantifying meltwater discharge from a tidewater glacier. Insights to glacier hydrology can also be obtained when surface processes are also considered. This furthers the understanding of tidewater glacier hydrology, which is valuable for improving the accuracy of sea level rise predictions.

Currently there is no extended study that explicitly focuses on themagnitude, frequency and timing of glacial calving resulting from externalforces. Past studies have identified the size and timing of calving events butthe links between them and the external factors that cause them are stillmissing. Here I present a method to identify the size, time and frequency ofcalving events on the Rink Glacier in Greenland. Using time lapse imagesspaced 30 minutes apart of the calving front, coupled with weather and tidedata, I plan on identifying the main driving force for calving. Results showthat atmospheric pressure and temperature have no positive correlation withcalving magnitude or size. Tidal influences and sea surface temperatureappear to have the strongest influence on the frequency of calving. As seasurface temperatures rapidly decrease though the study period, calvingfrequency also reduces. Strong calving correlations for the entire studyperiod were difficult to identify for tidal influences, as images could only betaken during the sunlit periods of the day. As this study was conductedduring autumn when atmospheric temperatures remained below 0°C, theavailability of melt water for crevasse creation and basal lubrication was notpresent. Therefore it is suggested that future studies on glacial stabilityshould use external forces to measure ice loss over the entire calving season.

Most vehicular tunnels, due to their restrictive and confined environment require continuous traffic surveillance and control. This is achieved by a variety of systems like closed circuit TV monitoring, personnel stationed in the tunnel, overheight & speed detectors and others. Traffic flow data were obtained from the Interstate 64(I -64) Hampton Roads Bridge-Tunnel. The data were analyzed and conclusions were drawn about traffic flow behavior at the different tunnel sections. During the operation of a tunnel, capacity reductions are often experienced due to temporary lane closures. These could result from incidences occurring in the tunnel area or due to regular maintenance activities. This work concentrates on the former case. A microcomputer model called Queue and User Cost Evaluation of Work Zones(QUEWZ) was employed in studying lane closure scenarios for the Virginia Tidewater Area Tunnels. In case of significant capacity reductions or complete blockages of directions of travel, it is desired to know beforehand the impact expected on the surrounding network. Traffic management actions like rerouting policies could be implemented and thus alleviate the problem. MASSVAC2, a computer simulation model for mass evacuation under emergency conditions was employed for analyzing different traffic management scenarios. / M.S.

I use time-constrained sediment volumes delivered by glaciers calving into Marinelli Fjord (55°S), an outlet glacier of the Cordillera Darwin Ice Cap, Southern Patagonia, to determine erosion rates across different timescales. These results indicate that modern sediment yields and erosion rates from temperate tidewater glaciers can exceed long-term values over the time of deglaciation after the LGM (centennial and millennial time scales) by up to two orders of magnitude. In northern Patagonia (Gualas glacier area, 46.5°S), an overall increase in sediment production in the late Holocene is interpreted as result of a sharp increase in centennial timescale precipitation (intensified westerly winds). Erosion rates values span two orders of magnitude from 0.03 mm/yr for Lapeyrere Bay at Anver Island (~64.5°S), up to 1.09 mm/yr for San Rafael glacier at northern Patagonia (~46.5°S). Rates from the Antarctic Peninsula glaciers are in general lower than the temperate Patagonian glaciers. A good correlation of erosion rates and modern (estimated sea level annual 1970 temperature) sea level annual temperature was found. Latitudinal decrease of millenial is interpreted as result of decreasing annual temperature although decreasing in annual precipitation is suggested. The pattern of thermochronology ages from other studies (Thompson et al., 2010; Guenthner et al., 2010), along with the values of 10 3 and 10 6 years timescales erosion rates from this study, indicate that long-term glacial erosion decreases significantly its efficiency with latitude, implying that long-term glacial cover acts as a protective blanket, hindering erosion and allowing mountain growth. We conclude that the pattern of erosion rate decrease with timescale reflects the sensitivity of glaciers to climate variability. Temperate glaciers have higher sensitivity and greater response amplitude to climatic stress than subpolar or polar glaciers. This results in a decrease in erosion rates (sediment production) with latitude, and also in a decrease of erosion rate gradients with timescale.

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (leaves 51-55). Also available via the World Wide Web.

No description available.

The recent thinning, acceleration and retreat of tidewater glaciers around Greenland suggests that these systems are highly sensitive to a change in climate. Tidewater glacier dynamics have already had a significant impact on global sea level, and, given projected future climate warming, will likely continue to do so over the coming century. Understanding of the processes connecting climatic change to tidewater glacier response is, however, at an early stage. Current leading thinking links tidewater glacier change to ocean warming by submarine melting of glacier calving fronts, yet the process of submarine melting remains poorly understood. This thesis combines modelling and field data to investigate submarine melting at tidewater glaciers, ultimately seeking to constrain the sensitivity of the Greenland Ice Sheet to climate change. Submarine melting is thought to be enhanced where subglacial runoff enters the ocean and drives energetic ice-marginal plumes. In this thesis, two contrasting models are used to examine the dynamics of these plumes; the Massachusetts Institute of Technology general circulation model (MITgcm) and the simpler buoyant plume theory (BPT). The first result of this thesis, obtained with the MITgcm, is that the spatial distribution of subglacial runoff at the grounding line of a tidewater glacier is a key control on the rate and spatial distribution of submarine melting. Focussed subglacial runoff induces rapid but localised melting, while diffuse runoff induces slower but spatially homogeneous melting. Furthermore, for the same subglacial runoff, total ablation by submarine melting from diffuse runoff exceeds that from focussed runoff by at least a factor of five. BPT is then used to examine the relationship between plume-induced submarine melting and key physical parameters, such as plume geometry, fjord stratification, and the magnitude of subglacial runoff. It is shown that submarine melt rate is proportional to the magnitude of subglacial runoff raised to the exponent of 1/3, regardless of plume geometry, provided runoff lies below a critical threshold and the fjord is weakly stratified. Above the runoff threshold and for strongly stratified fjords, the exponent respectively decreases and increases. The obtained relationships are combined into a single parameterisation thereby providing a useful first-order estimate of submarine melt rate with potential for incorporation into predictive ice flow models. Having investigated many of the factors affecting submarine melt rate, this thesis turns to the effect of melting on tidewater glacier dynamics and calving processes. Specifically, feedbacks between submarine melting and calving front shape are evaluated by coupling BPT to a dynamic ice-ocean boundary which evolves according to modelled submarine melt rates. In agreement with observations, the model shows calving fronts becoming undercut by submarine melting, but hints at a critical role for subglacial channels in this process. The total ablation by submarine melting increases with the degree of undercutting due to increased ice-ocean surface area. It is suggested that the relative pace of undercutting versus ice velocity may define the dominant calving style at a tidewater glacier. Finally, comparison of plumes modelled in both MITgcm and BPT with those observed at Kangiata Nunata Sermia (KNS), a large tidewater glacier in south-west Greenland, suggests that subglacial runoff at KNS is often diffuse in nature. In addition to the above implications for submarine melting, diffuse drainage may enhance basal sliding during warmer summers, thereby providing a potential link between increasing atmospheric temperature and tidewater glacier acceleration which does not invoke the role of the ocean. This thesis provides a comprehensive investigation and quantification of the factors affecting submarine melting at tidewater glaciers, a complex process that is believed to be one of the key influences on the current and future stability of the Greenland Ice Sheet. Based on the magnitude of modelled melt rates, and their effect on calving front shape, the process of submarine melting is a likely driver of retreat at slower-flowing tidewater glaciers in Greenland. For melting to influence the largest and fastest-flowing glaciers requires invoking a sensitive coupling between melting and calving which is as yet obscure. It should however be noted that modelled melt rates depend critically on parameters which are poorly constrained. The results and parameterisations developed in this thesis should now be taken forward through testing against field observations - which are currently rare - and, from a modelling perspective, coupling with ice flow models to provide a more complete picture of the interaction of the Greenland Ice Sheet with the ocean.