Imprints of Ice Dynamics and Atmospheric Signals on the internal structure of Antarctic Ice as seen via Radar
Different electromagnetic reflection methods can operate from satellites, airplanes or ground vehicles to illuminate the surface and the inside of ice sheets across varying spatial scales. The backscattered signal is formed by micro-physical ice properties, many of which in turn are influenced by me...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Universität Bremen
2011
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| Online Access: | https://media.suub.uni-bremen.de/handle/elib/211 https://nbn-resolving.org/urn:nbn:de:gbv:46-00102292-12 |
| Summary: | Different electromagnetic reflection methods can operate from satellites, airplanes or ground vehicles to illuminate the surface and the inside of ice sheets across varying spatial scales. The backscattered signal is formed by micro-physical ice properties, many of which in turn are influenced by mechanisms operating on a macro-scale: the alignment of crystal orientation fabric (COF) depends on the specific strain regime and the initial impurity loading; the pattern in internal layering is imprinted by accumulation and the surrounding flow regime; the brightness of the bottom reflection over ice-shelves depends on the melting or refreezing of platelet ice which is susceptible to changing ocean currents and grounding line positions. The study is subdivided in five chapters which have been or will be published separately. All studies focus on the link between these small-scale features and their large-scale expressions. The synthesis of the different methods improves the capability of remote sensing to deliver variables from which the current state of the cryosphere can be determined. The study contributes to assimilating geophysical data into the coming generation of ice-dynamic models which improve the understanding of ice-sheet histories and prognose their future behaviour. The starting point is the appearance of the radio-echo free zone (EFZ), which is a feature-less band observed above the ice--bed interface in many radargrams across Greenland and Antarctica. The comparison of the EFZ onset with optical ice-core images yields a connection between the mm-cm scale disturbances in the core's stratigraphy and the disappearance of radar reflection horizons. This is evidence that ice flow can disturb internal ice layering, which hampers the derivation of a coherent age--depth scale and indicates a changing flow behaviour with depth. A polarimetric radar survey in the same study area shows that backscattered power varies with the horizontal orientation of the antennas (i.e. with the polarization plane). Extrema in ... |
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