Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 61-63). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 61-63). Also available on the Internet.

The West Greenland coast is a typical fjord region with a considerable development of local deepwater basins. The majority of the West Greenland fjords are of the typcial bottom configuration, with a well-developed threshold at the mouth, which normally rises to within 100 or 200 m of the surface. Such a fjord has been named an "Arctic" type fjord by Stephensen (1916), because the bottom water is arctic in character, having a negative temperature and low salinity. Ameralik fjord (Latitude 64o 3' N., Longitude 52o 30' W.) (map) is in this category. [...]

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No description available.

The aims of this thesis was to participate in the improvement of the current knowledge of tidewater glaciers' behaviour in Greenland. This was achieved by a multi-scale and multi-disciplinary approach.

Contemporary observations show an increase in the melting of the Greenland Ice Sheet (GrIS) since the early 21st century. Located near the critical sites of oceanic deep convection and deep water formation, the melting of the GrIS has the potential to directly impact the Atlantic Meridional Overturning Circulation (AMOC) by freshening ocean surface waters in these regions. The majority of the Coupled Model Intercomparison Project Phase 5 (CMIP5) models project a decline in AMOC strength by 10-50% during the 21st century, in response to the increase in atmospheric greenhouse gas (GHG) concentrations. However, due to the simple treatment of polar ice sheets and the lack of a dynamical ice sheet component in these models, these projections likely underestimated the impacts of the GrIS melt, leading to uncertainty in projecting future AMOC evolution and climate change around Greenland. To better understand the impact of the GrIS melt on the AMOC, we perform a series of 21st century projection runs with a state-of-the-art Earth System Model-GFDL ESM2Mb. We consider a medium and a high Representative Concentration Pathway (RCP) scenario (RCP4.5 and RCP8.5, respectively). Unlike the CMIP5-standard RCP runs which included only radiative forcing, the new model experiments are also forced with additional and potentially more realistic meltwater discharge from the GrIS. This meltwater discharge is estimated based on a model-based relationship between the GrIS surface melt and the 500hPa atmospheric temperature anomalies over Greenland. The model simulations indicate that compared to the RCP4.5-only and RCP8.5-only projections, the additional melt water from the GrIS can further weaken the AMOC, but with a relatively small magnitude. The reason is that radiative forcing already weakens the deep convection and deep water formation in the North Atlantic, therefore limiting the magnitude of further weakening of AMOC due to the additional meltwater. The modeling results suggest that the AMOC's sensitivity to freshwater forcing due to the GrIS melt is highly dependent on the location and strength of oceanic deep convection sites in ESM2Mb as well as the pathways of the meltwater towards these regions. The additional meltwater contributes to the minimum surface warming (so-called "warming hole") south of Greenland. These simulations with ESM2Mb contribute to the Atlantic Meridional Overturning Circulation Model Intercomparison Project (AMOCMIP), a community effort between international modeling centers to investigate the impacts of the melting of the GrIS on the AMOC and quantify the associated uncertainty.

The Motzfeldt centre is one of four major alkaline centres belonging to the Igaliko complex of South Greenland. The melts parental to the Motzfeldt centre are interpreted from Hf isotopes to be derived form a common mantle source which experienced subsequent isotopic contamination from older crustal components during the interval between segregation and emplacement. Magmatism within the centre commenced with the emplacement of the Motzfeldt Sø Formation at 1273 ± 8 Ma. This unit is unique within the Motzfeldt intrusion as it is characterised by a high degree of textural and mineralogical variability and hosts localised Nb, Ta, U, Th, Zr and REE mineralisation associated with pyrochlore and late-stage REE bearing carbonate phases. Biotite halogen contents show that in addition to enrichment of incompatible elements the MSF and Motzfeldt centre in general is particularly rich in F. The elevated F content is inferred to have extended the crystallisation interval of the melt and facilitated fractionation down to relatively low temperatures. The unusual enrichment of F and incompatible elements in the MSF is suggested to represent the first and most evolved melts extracted from the top of a stratified storage chamber at depth. The MSF is also characterised by pervasive subsolidus alteration, giving the rock and region a striking brick red colour. Pb-Pb pyrochlore studies indicate that alteration in the formation was effectively synchronous (1267 ± 6 Ma), with the magmatic age of emplacement. Fluid inclusion studies suggest that contemporaneous to the exsolution of juvenile, high salinity, F-rich fluids was the wholesale influx of hydrothermally convected low salinity groundwaters through the formation. The presence of pervasive late-stage hematite and calcite throughout the MSF suggests that the oxidation potential of the bulk fluid increased above the hematite-magnetite buffer during the waning stages of the hydrothermal phase. Mineralisation was promoted by this shift in fluid composition, reducing the complexing potential of fluid ligands and facilitating mineralisation within the high-levels units of the intrusion where alteration is most intense. Economic mineralisation associated with the centre is inferred to be largely sourced from the parental melts, however the role the hydrothermal phase played was particularly important in locally mobilising and concentrating incompatible elements within the high-level units of the formation.

This thesis tests and applies a new, physically based snow distribution and melt model at spatial scales of tens of metres and temporal scales of days across sub-arctic landscapes, in order to assess the significance of snow variability in sub-arctic human ecodynamics at resolutions relevant to human activities. A wider goal is to contribute to planning in the face of future climate change. Model tests are undertaken based on original field data collected in Sweden and Norway, and secondary data from Idaho, France and Greenland. Model applications focus on the ‘completed experiment’ of the medieval Norse in Greenland, a comparatively isolated population that relied on a combination of pastoralism and hunting for survival. A combination of local calibration based on contemporary meteorological data, customised climate reconstructions based on GCM data, new archaeological survey and new DEM are used in order to apply the model. This thesis shows, for the first time, the likely range of snow depth and duration experienced across the medieval Norse Greenland landscape as a result of climate and vegetation change. Results show that increases in snow cover could have been significant drivers of transformative change in Norse Greenland, and are therefore likely to be key in understanding the potential impact of future climate changes on similar sub-arctic and relatively marginal communities. Selected model analyses simulate the total spring (April-June) snow cover at the homefields to range from 32% cover lasting 6 days in the most favourable climate to 100% cover lasting 45 days in the most unfavourable climate at key elite inner fjord farms. At the more isolated outer fjord farms, total spring snow cover ranges from 33% cover lasting 10 days in the most favourable climate to 100% cover lasting 60 days in the most unfavourable climate. Increased climate variance and recovery times, as experienced by the Norse, are potential early warning signals of threshold-crossing change. Model results show that these signals could have been masked for the Norse decision making elite because they were located in the most favourable and least snow covered locations. Masking could have been further increased through the intensified seal hunting implemented by the Norse as an adaption strategy, and these actions could have developed into a rigidity trap. When the conjunctures of the 15th century developed in terms of increased sea ice, snow cover, storminess, culture contact, changing trade and sea level rise, it was too late to develop different responses. Whilst current populations have improved technology and knowledge relative to the Norse Greenlanders, there is a risk that adaptations will lack long-term utility, spatially restricted indications of change may be ignored, and rigidity traps develop. This thesis provides an additional tool for understanding a key element of both the past and possible futures of subarctic human ecodynamics.