The ultimate scientific objective of this study is to investigate a new high frequency radar array technology for characterizing temperate glaciers by mapping bed topography, basal ice hydrologic features, the thickness and distribution of saturated tills, and deep englacial drainage channels. It is widely acknowledged that presently there are no effective direct, or remote methods capable of delineating these structures. Radar methods fail because of the intrinsic high noise properties of temperate glaciers. Modern radar instruments have overcome random noise and antenna noise problems. The current limitation on radar is noise resulting from subsurface water inclusions, which impose a 10 MHz upper frequency limitation on conventional temperate glacier surveying methods. A radar survey method utilizing array processing can significantly suppress noise from water filled scattering inclusions. Numerical models and time domain data processing algorithms will be developed to guide the array design, performance analysis, and interpretation procedures. In addition, a physical scale model of a temperate glacier will be used to collect radar data in the millimeter wave frequency (30 GHz) range. The physical model results will be used to verify numerical and theoretical array processing results and further refine the approach. A field experiment will be carried out on the shallow (100 - 200m), readily accessible, Gulkana glacier, Alaska. This field experiment will include conventional radar and radar array data collection methods with 100 MHz antennas. In the field operations they will be specifically interested in demonstrating the improved depth of penetration using the array method as compared to the conventional technique. The immediate glaciologic benefits will be an accurate picture of how near surface englacial and basal ice water channels are interconnected and oriented on a small, but interesting temperate glacier. The extended benefit will be the development of a practical method for sounding much deeper temperate glaciers. For example, on very deep (1000 m) temperate glaciers they believe the high frequency radar array could operate at a center frequency around 30 MHz. In this band, multiple radar array stations, or a towed array, would have the potential to define, characterize, and spatially map meter scale englacial and basal ice hydrologic features as well as ice bed topography.. This is particularly relevant since the depth and bottom topography of almost all large subpolar ice fields are unknown. In addition, a high resolution deep penetration radar capability applied to large ice masses would help answer questions about steady flow and surge mechanisms, basal freeze, and sediment transport. The radar array technique will also be applicable to Antarctic glaciers.
