USING GROUND PENETRATING RADAR TO AID IN THE MODELING OF SHALLOW WATER SEDIMENTATION AND PERMAFROST GROWTH IN THE MACKENZIE DELTA, CANADA

Permafrost is know to extend out into the shallow water areas in the Arctic. This can include lakes rivers and deltas. Due to rapid sedimentation, the shallow water zone (i.e. water depths less than 2 m) in the Mackenzie Delta in the western Canadian Arctic is very extensive, extending up to 15 km seaward of the coastline. As well, the bathymetry in this zone is complex and has been known to change dramatically over short periods of time. Following in the footsteps of Professor Derald Smith, Ground-Penetrating Radar (GPR) surveys were undertaken to map bathymetric changes and the presence and depth of frozen ground.

The results of repeated GPR surveys revealed a number of remarkable aspects of this deltaic system. First, the bathymetry and hence the zone of bottom-fast ice varied dramatically both spatially and temporally. Second, thermal reflections could be easily distinguished from sedimentary reflections in the sub-bottom sediments. Using the GPR results as input into a thermal model, the distribution of sub-bottom frozen ground could be modeled from the water depth and the seasonal ice-contact time.

By combining the geophysical data with multi-temporal remotely sensed synthetic-aperture radar (satellite SAR) data, shallow water bathymetric maps and permafrost aggradation and degradation maps were able to be created for large areas. As such, the changes in sedimentation and permafrost conditions in the shallow water zone can now be monitored from year to year in response to changing hydrological and climatological conditions.