Accurately forecasting the contribution of the Greenland Ice Sheet to global sea-level requires precise observations to constrain present-day processes and incorporate them into models. However, the spatial and temporal resolution of satellite imagery and representativeness of in situ measurements often precludes or obscures our understanding of mass loss processes. This thesis investigates whether imagery from unmanned aerial vehicles (UAVs) have the potential to 1) bridge the scale gap between in situ and satellite observations and, 2) resolve processes of mass loss which are beyond the resolution of satellite imagery. It is found that the footprints of ground-based pyranometers are insufficient to capture the spatial heterogeneity of the ice surface as it progressively ablates and darkens. Point-to-pixel albedo comparisons are therefore often invalid, meaning that satellite-derived albedo measurements may be more accurate than previously thought. A 25 km transect intersecting the dark zone reveals that distributed impurities, not cryoconite nor surface water, govern spatial albedo patterns and may have implications for the future expansion of the dark zone. Repeat surveys over Store Glacier show that UAVs can be used to quantify calving rates and surface velocities of tidewater glaciers. The surveys indicate that large calving events cause short-term terminus velocity accelerations and can explain the seasonal pattern of acceleration and retreat. Any process which accelerates calving, such as removal of the ice m ́elange, therefore has important implications for the glaciers future behaviour.

A criterion is defined to compare seasonal ice coverage in the Greenland Sea for the years 1900-57, and the areal coverage is graphed using the 1898-1913 average as a standard. The factors wielding possible influence on short-term variations of the ice cover are examined individually and their relative importance established. The influence of ocean currents is evaluated by analysis of hydrosections across the East Greenland Current at 74°-76° N and across the North Atlantic Current in the Faeroe-Shetland channel. Data from the latter area are used for numerical analysis of heat imported to the Greenland Sea by the North Atlantic Current in the 1927-52 period. Details about the Irminger Current's behavior are derived from station data from Denmark Strait and from surface temperatures at Selvogsbanki south of Iceland. Year-to-year variations are found to exist in the flow volumes of all three currents, and correlations with seasonal ice coverage in the Greenland Sea are shown. Above-average precipitation in conjunction with below-average storm activity is found to have negligible influence on the ice regime, and no significant correlation is found. The possible effect of evaporation is computed to be far below the threshold of detectability. Air temperatures in the Norwegian-Greenland Sea region display a trend of increase throughout the period studied, in harmony with a concurrent trend of decreasing ice cover; but no causal relationship is in evidence. The effects of strengths and directions of predominant winds are examined, and good correlations are shown between ice cover fluctuations and easterly wind components at Norwegian coastal stations. At the points of major currents' entrances to and exits from the Greenland Sea the wind effects are complex and cannot be fully evaluated on the basis of existing data. The fluctuations of ocean currents entering and leaving the Greenland Sea and of water movements within the Greenland Sea remain as the apparent determinant of year-to-year variations of the ice cover. / Graduation date: 1968

The aim of this report is to describe the deglaciation in an area on west Greenland in the vicinity of Kangerlussuaq. To do this, the geomorphological landforms were mapped by studying areal photographs and by a two week field study where key areas were examiend. The landforms were transferred to a map using ArcGis and each key area were interpreted.The majority of the geomorphological formations were formed during the last deglaciation and consists of morain ridges, kettle topography in both till and glacifluvium, glacifluvial deltas, two fossil sandurs, and lateral terraces. Based on key areas and an inversion model a geomorphological map was created to illustrate the deglaciation, using the least complex explanation of the genesis of the landforms. The results show that the ice played a major role by damming lakes which enabled formation of many meltwater chanels and delta formations on higher elevations. The morain ridges and lateral terraces showed the extent of the ice margin during the halts in the ice retreat. The deglaciation was dated with help from earlier studies and the conclusion was that the deglaciation started between 7900 and 6700 yr BP. And the area was free from ice 7100-6500 yrs BP.

No description available.

Thesis (M.S. in Physical Oceanography and Meteorology)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Bourke, Robert H. ; Paquette, Robert G. "September 1990." Description based on title screen viewed on December 16, 2009. DTIC Descriptor(s): Polar regions, *deep water, dynamics, water, rates, arrays, surfaces, fresh water, drift, ice, surveys, surface waters, high density, transport, patterns, thinness, barometric pressure, Atlantic ocean, sea water, height, basins(geographic), Eurasia, gradients, Greenland sea, Lagrangian functions, Greenland, cores, water analysis, temperature DTIC Identifier(s): Jan Mayen current, *ocean currents, *sea water, *water analysis, oceanographic data, electrical conductivity, temperature, density, transport properties, east Greenland current, Greenland sea, theses Includes bibliographical references (p. 137-139). Also available in print.

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The purpose of this thesis is to investigate the hydrology and dynamics of a land-terminating outlet glacier on the western margin of the Greenland Ice Sheet (GrIS). The investigations are motivated by uncertainty about the effect of meltwater on rates of ice flow in the GrIS and the possibility that hydrologically forced changes in ice velocity might increase mass loss from the ice sheet significantly in response to climate warming. The impact of meltwater on fluctuations in ice flow has been a research focus for glaciologists studying Alpine and Arctic glaciers for decades. In these settings, one of the main controls on the relationship between surface melting and ice velocity is the structure of the subglacial drainage system, which evolves spatially and temporally on a seasonal basis in response to inputs of meltwater from the glacier surface. In this thesis we present three years of field observations of glacier velocity, surface ablation and hydrology from a land-terminating glacier in west Greenland. These data are supplemented by satellite data and the use of simple models to constrain surface melting. We find that hydrologically forced ice acceleration occurs each year along a 115 km transect, first at sites nearest the ice sheet margin and at locations further inland following the onset of surface melting at higher elevations. At sites near the ice sheet margin, the relationship between surface melting and ice velocity is not consistent throughout the melt season, and ice velocity becomes less sensitive to inputs of meltwater later in the summer. This is explained by development in the efficiency of the subglacial drainage system, in a manner similar to Alpine glaciers. We perform a hydrological study which indicates that an efficient subglacial drainage system expands upglacier over the course of the melt season, in response to inputs of water from the ice sheet surface. At higher elevation sites, however, thicker ice and colder temperatures mean that it is harder to generate enough water to reach the ice-bed interface and this only occurs once enough water has accumulated to propagate fractures through thick ice to the bed. One mechanism which allows this is drainage of supraglacial lakes. Inter-annual comparison shows that increased rates of annual ablation lead to higher annual ice velocities. At high elevation sites (>1000 m), timing of drainage of meltwater to the ice-bed interface appears to be the main control on the the overall magnitude of summer acceleration. At lower elevations, although development in the structure of the subglacial drainage system limits the overall summer acceleration signal, short-term variability in meltwater input can sustain high ice velocities even once the subglacial drainage system has become channelised. Overall, the research presented in this thesis suggests that hydrologically-forced acceleration can increase mass loss from the GrIS in a warmer climate due to inland expansion of the area of the ice sheet bed which is subject to inputs of meltwater from the ice sheet surface. The relationship between surface melting and ice velocity is mediated, however, by the structure of the subglacial drainage system and variations in the rate of meltwater drainage to the ice bed interface. Insights from this work can help in the development of numerical ice sheet models which aim to predict the future contribution to sea-level rise from the Greenland Ice Sheet.

No description available.

No description available.

No description available.