Bestimmung der Meereisdicke mit seismischen und elektromagnetisch-induktiven Verfahren

• Main Author: Haas, Christian
• Format: Thesis
• Language: unknown
• Published: 1997
• Subjects: ice core; Polar Research; Sea ice
• Online Access: https://epic.awi.de/id/eprint/1141/; https://epic.awi.de/id/eprint/1141/1/Haa1997b.pdf; https://hdl.handle.net/10013/epic.11730; https://hdl.handle.net/10013/epic.11730.d001

Thickness is an important parameter for the description of sea ice. Its spatial and temporal distribution modifies the interaction between ocean, ice and atmosphere. Knowledge of the ice thickness distribution is of particular importance for observations of climatic changes, validation of sea-ice and general circulation models as well as for human activities in the polar regions.So far, only few operational techniques for the determination of ice thickness distributions exist. Thus, there is still a great need for the development of accurate and simple, generally applicable methods.In this thesis, two geophysical methods, a seismic and an electromagnetic-inductive technique, are examined for their accuracy and general applicability. Both aspects are investigated by means of comparisons of drill-hole deter-mined with geophysi-cally derived thicknesses along extended profiles. Additionally, the thickness range, resolution and sensitivity against variable ice properties are examined by means of theoretical model calculations.The porosity of the ice and its electrical conductivity are derived by means of ice core analyses. These are the main variables influencing the propagation of elastic waves and the development of electromagnetic fields in the ice.With the seismic measurements ice thickness is determined from the dispersion of surface waves. On average, derived thicknesses underestimate the true thickness by about 20%. The lateral resolution is not better than 20 m. Due to its high porosity during summer the ice strength is very reduced. This considerably hampers the propagation of elastic waves such that ice thickness can hardly be determined during this season.Execution and analysis of the measurements are involved. Nevertheless, the seismic technique is the only one which yields information about bulk elastic parameters of larger ice areas. Here, such parameters are calculated from propagation velocities for summer and winter first- and multi-year ice.Electromagnetic induction measurements make use of the ...