An iceberg isn’t just a threat to unsinkable ships. Coastal cities are at risk for their ability to cause underwater landslides.
As a result of earthquakes, landslides can occur on the ocean floor, which can cause tsunamis.
Researchers found that drifting icebergs can create submarine landslides when they capsize and hit the ground. As oceans warm, the number of icebergs is increasing, making a previously unknown geohazard.
The world’s most enormous iceberg was set to break loose from the western side of Antarctica’s Filchner-Ronne Ice Shelf in May 2020. In the middle of the Weddell Sea, A-76, the largest iceberg in history, had a width of 15 miles and an area of 1667 square miles. Global warming is causing significant chunks of Antarctic ice to melt at an alarmingly rapid rate.
The bottom of the ocean can be scraped by icebergs that are deep enough. The extreme quantities of water they displace can threaten ships and damage structures similar to platforms and undersea internet cables. They may be large enough to cause tsunamis as they splash into the sea.
Now a new study has revealed that smaller icebergs, chunks whose keel does not even touch the bottom, can cause underwater landslides when they hit a shoreline and capsize, possibly causing a tsunami. There is an underestimated geohazard here.
According to the study, “Icebergs originating from the Arctic, Greenland and Antarctica are hazards thousands of kilometers away from their original source and can affect continental slopes by triggering submarine landslides.”
The iceberg is coming
The worrying insight was revealed from some detective work that demonstrated an underwater landslide that occurred somewhere between September 2018 and September 2019, along the Southwind Fjord near Nunavut’s Baffin Island.
It is notoriously difficult to analyze marine landslides due to their usually unseen nature. A geological mystery was solved using satellite data, bathymetric data, and analyses of the composition of the local seabed.
A comparison of high-resolution, multibeam echosounder data of the fjord’s seabed taken in 2013, 2014, 2018, and 2019 revealed the telltale signs of the landslide. “Featureless” seabeds were depicted in the earliest seabed paintings. Two more minor scarps, however, had been found by the later readings.
According to the story, a primary landslide occurred between August 27, 2018 (the date of the 2018 bathymetric survey) and September 24, 2019 (the date of the next bathymetric survey). At the same time, there was also evidence of two adjacent landslides, which occurred when the two smaller scarps failed. During this period, no large earthquakes have been reported within 300 kilometers of the fjord.
There was, however, a geological smoking gun: the scientists observed 20-27-meter-deep iceberg pits, depressions indicative of an iceberg impact.
Captured on camera
According to Sentinel 2 satellite images, the perpetrator entered the fjord in August 2018, became grounded between September 1-4, and was no longer visible by early October. In September 2018, the interloper ran into the ice pits 3 meters upslope and then 3 meters downslope – lining up perfectly with the seabed data – and went downslope three days later. According to the narrative, the iceberg capsized between September 4 and 9, hit the seafloor, and broke into two pieces.
Not just A threat to unsinkable ships
According to the study, landslides beneath the sea surface are not caused only by earthquakes but also by subaquatic phenomena. As icebergs floated into shallow water, the damage was believed to be limited to continental shelves and upper slopes.
As a result, the study concluded: “These results indicate that icebergs grounding and capsizing may be responsible for triggering submarine landslides in many fjords and on continental slopes in polar to sub-polar environments, representing a previously underestimated hazard.”
Coastal cities, be on the lookout for wandering icebergs.