SUBMARINE LANDSLIDES IN GLACIATED ENVIRONMENTS: NEW TRIGGERS IDENTIFIED THROUGH REPEAT MULTIBEAM SURVEYS

Submarine landslides are among the largest geological hazards on Earth and represent a threat to coastal populations through the generation of tsunamis and to offshore infrastructure such as subsea internet cables and oil and gas infrastructure. Earthquakes are often cited as the main trigger of submarine landslides; however, contrary to their terrestrial counterpart, it is often impossible to link submarine landslides to specific earthquakes or other trigger mechanisms since it is extremely rare that new landslides are observed underwater in near real-time. In order to understand triggers of submarine landslides in polar and sub-polar glaciated environments, a monitoring project began in Southwind Fiord (Baffin Bay) where a great number of apparently recent landslides have been identified at the sea bed on the underwater fiord slope. The monitoring project included repeat seafloor surveys which revealed new submarine landslides triggered between September 2018 and September 2019. Although Baffin Island is located near an active seismic zone, no significant earthquakes were recorded between these two dates, suggesting another mechanism triggered the landslide. Repeat multibeam bathymetry shows that this new landslide is associated with newly formed iceberg grounding pits at its headscarp. The exact iceberg responsible for these new pits was then identified through the analysis of Sentinel 2 satellite imagery, which showed that the iceberg grounded in early September 2018. Geotechnical data from a nearby sediment core reveals that the fiord sediments are susceptible to failure, suggesting that the vertical loading induced by the iceberg grounding in early September 2018 was sufficient to trigger the observed landslide. As iceberg discharge from Greenland and Antarctica is believed to increase due to climate change, submarine landslides from iceberg groundings may represent a seafloor hazard for coastal communities and the development of polar to sub-polar marine infrastructure.