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Maritime

Seafloor Mapping in Permafrost

The Alfred Wegener Institute for Polar and Marine Research (AWI) in Germany has engaged in the coastal permafrost erosion research project (COPER) funded by the Helmholz Association and the institute. Kongsberg Geoacoustic's GeoSwath Plus Compact system is playing a vital part in this important project.

The survey vessel is an inflatable craft with the GeoSwath Plus Compact sonar head installed on a retractable pole together with peripheral sensors, motion reference unit, GPS and sound velocity probe. The splash protected deck unit is powered by batteries and operated via a ruggedized laptop. Alfred Wegener Institute for Polar and Marine Research. Photo: S. Weege.
Bathymetry map of Pauline Cove on Herschel Island, YT, Canada. The area was chosen as the natural laboratory for coastal erosion processes in permafrost regions. The bathymetry is the baseline for long term studies. Note the dredge marks caused by the sea ice processes. Alfred Wegener Institute for Polar and Marine Research, Boris Radosavljevic.

A stark seasonal contrast characterizes coastal dynamics on arctic coasts. During the winter the coast is protected by sea and landfast ice. In absence of ice the coast is exposed to mechanical and thermal erosion processes with high erosion rates. Forecasts of many climate change models indicate that the Arctic region will experience disproportionate warming in coming decades, which will further increase the rate of coastal erosion and also liberate vast quantities of carbon stored in permafrost leading to an important potential climate feedback, as the carbon released from permafrost might contribute further to the warming trend.

The research project looks to describe and quantify the erosion and related carbon release by using air- and space- born methods together with field research. Herschel Island in the Beaufort Sea, Yukon Territory, Canada, was selected as a natural laboratory for the long term field study.

An integral part of the fieldwork is seafloor mapping for which AWI has chosen the Kongsberg GeoAcoustics GeoSwath Plus Compact system. The system delivers high resolution bathymetry with coverage of up to 12 times the water depth in this shallow water environment and co-registered geo-referenced side scan data, which can be used for detailed seafloor classification.

In the 2012 field season c. 3.1 km2 has been collected, mapping Pauline Cove with water depth of 1 - 17 m in five short survey days. This dataset represents a baseline to which future surveys can be compared to. Future expeditions are planned to re-survey and expand the area to other parts of the island.

Decisive factors in operating in remote and harsh environments are the portability and reliability of the equipment. The remote location makes it necessary to airlift all equipment and personnel. The survey was carried out with an inflatable craft on which the splash protected (IP54) system was installed in a portable installation and powered by 24 V battery.