Iceberg discharge influences ocean circulation, affects climate and increases global sea level. Icebergs are also known to gouge the seafloor in water depths limited by their keel depth, thus representing a hazard to subsea infrastructure. Here, we provide evidence that icebergs can affect the seafloor at depths greater than their keel depth by triggering submarine landslides. Using repeat bathymetric surveys from multibeam echo sounders, we investigate the cause of a submarine landslide that occurred in Southwind Fjord, Baffin Island, between September 2018 and September 2019. This landslide is shown to be closely associated with recently formed iceberg pits at its headscarp carved by an iceberg that grounded and that capsized in the fjord in early September 2018. Geotechnical data from a nearby sediment core indicate that the vertical loading induced by the iceberg grounding and capsizing is sufficient to trigger the observed landslide. These results imply that icebergs originating from the Arctic, Greenland and Antarctica are hazards thousands of kilometres away from their original source and can affect continental slopes by triggering submarine landslides. This process represents an additional source of marine geohazards, especially if climate change leads to increased iceberg discharge.
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The multibeam data are available from Amundsen Science (https://amundsenscience.ulaval.ca/data/data-access/) and from the Geological Survey of Canada Expedition Database (https://ed.gdr.nrcan.gc.ca/). Online visualization of pre-landslide data can be done from the University of New Brunswick Ocean Mapping Group (http://www.omg.unb.ca/Projects/Arctic/SE_Baffin/). All other data are available from the Geological Survey of Canada Expedition Database (https://ed-dev.gsca.nrcan.gc.ca/) under cruises 2018042 and 2019Nuliajuk or from the corresponding author. Satellite imagery is available at https://apps.sentinel-hub.com/eo-browser. All other relevant data are provided as Supplementary Data 1 and 2.
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This project was funded by the Program of Energy Research and Development of Natural Resources Canada, Crown-Indigenous Relations and Northern Affairs Canada, the Geological Survey of Canada (GSC) Public Safety Geoscience programme, the Government of Nunavut and ArcticNet. The Fisheries and Sealing Division, Department of Environment, Government of Nunavut is thanked for their support through the use of the RV Nuliajuk. We also thank the crew and scientific staff of the CCGS Amundsen, RV Nuliajuk and CCGS Hudson. This is NRCan contribution number 20200001
The authors declare no competing interests.
Peer review information Nature Geoscience thanks Jenna Hill, Jason Amundson and Morelia Urlaub for their contribution to the peer review of this work. Primary Handling Editor: James Super.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
a, Multibeam echosounder (MBES) bathymetry surveys were completed in 2013, 2014, 2018, and 2019 (red bars indicate dates of MBES surveys, blue indicates interval of time during which the submarine landslide was triggered according to MBES surveys). The new landslide was observed between the 2018 and 2019 multibeam surveys. b, Timing of satellite images without cloud cover (red bars indicate dates of satellite imagery, blue indicates the interval of time during which the submarine landslide occurred according to satellite imagery) showing the iceberg in Southwind Fjord and its grounding. Between 1 and 4 September 2018, the iceberg grounded upslope of the headscarp. Between 4 and 9 September 2018, the iceberg appears to have capsized and broke into two pieces. The iceberg is then at the landslide headscarp. The iceberg then remained grounded at the landslide headscarp until 1–13 October 2018.
a–c, Multibeam bathymetry images from 2013 (a), 2018 (b) and 2019 (c). d–f, Difference in elevation between 2013–2018 (d), 2018–2019 (e) and 2013–2019 (f). The difference in elevation shows the lack of seabed change between 2013 and 2018 and the erosion and deposition occurring between 2018 and 2019.
Extended Data Fig. 3 Satellite imagery showing iceberg drifting into Southwind Fjord on 27 August 2018 next to the CCGS Hudson.
(see inset of CCGS Hudson in (a). Subsequent images (c–f) show the iceberg grounded at the precise location where the submarine landslide was triggered.
Extended Data Fig. 4 Satellite imagery showing the iceberg entering and grounding in Southwind Fjord.
a, Sentinel 2 satellite imagery collected on 27 August 2018 showing the CCGS Hudson in Southwind Fjord and an iceberg to the north. b, Iceberg shown in A. c, Unammed Aerial Vehicle photography of the CCGS Hudson, its Fast Rescue Craft (FRC) and the iceberg illustrated in A. d, FRC next to the iceberg that serves as a scale to measure the approximate size of the iceberg (estimated at width of 35–40 m by 5 m high). These horizontal estimations were confirmed by satellite imagery dimension of the iceberg.
Geotechnical properties of sediment in Southwind Fjord, illustrating that the factor of safety reaches 1.8 at 295 cm.
Consolidation plot for sample 2018042–035, 246.0–248.5 cm. P’c is the preconsolidation pressure.
a, Effective overburden stress at each depth approximated using the depth to effective stress relationship from core 35. A normalized strength ratio of 0.3 was used to calculate the undrained shear strength at each depth for normally consolidated sediments b, Additional ice loads required for the sediment to fail calculated for failure depths of 5–15 m and slope angles of 5–15°. Equation 3 was used to estimate the additional load required to fail the sediments.
Extended Data Fig. 8 Examples of at least 16 submarine landslides along the eastern Canadian continental margin likely triggered by iceberg collision with the seafloor.
a, Multibeam bathymetry image of the Scotian Slope showing iceberg pits at the headscarp of submarine landslides. b,e,h, Multibeam bathymetry data of landslides 8, 15–16, 7, showing iceberg pits at the headscarp of submarine landslides. c,f,i, Downslope profiles of the landslides, illustrating the iceberg pits at the headscarps. d,g,j, Along-slope profiles of the iceberg pits at the headscarp and the failure depth of the landslides, illustrating their similar depth. The similar depth between the failure plane and the iceberg pits indicates that iceberg grounding or capsizing, as well as glacier calving, are a reasonable interpretation for the generation of these submarine landslides.
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Normandeau, A., MacKillop, K., Macquarrie, M. et al. Submarine landslides triggered by iceberg collision with the seafloor. Nat. Geosci. 14, 599–605 (2021). https://doi.org/10.1038/s41561-021-00767-4