A colossal tsunami, triggered by a massive rockfall in an Alaskan fiord last year, has been revealed in a recent study to be one of the most significant tsunamis on record, towering at a staggering 481 meters, taller than the highest observation deck of the CN Tower. The study, led by Dan Shugar, an associate professor at the University of Calgary, highlights the immense potential devastation of such waves and emphasizes the urgent need for policymakers, especially in British Columbia, to address the risks associated with them.
The research, featured in the Science journal, underscores that the southeast region of Alaska near the northwest B.C. border experienced this tsunami due to a glacier’s rapid retreat that cleared the path for the landslide. The study warns that with ongoing climate change and the expansion of infrastructure and cruise ship tourism, the danger of landslide-induced fiord tsunamis is escalating, potentially leading to future catastrophic events.
According to the study, the rockfall, totaling over 64 million cubic meters, plummeted 1,000 meters into the deep Tracy Arm Fjord at 5:26 a.m. on Aug. 10 of the previous year, resulting in a colossal wave with the second-highest run-up ever recorded, reaching approximately 481 meters. The fiord, usually frequented by three cruise ships daily, sees a surge in ship visits during the summer months, with over 20 ships navigating Tracy Arm and nearby Endicott Arm fiords each day.
Fortunately, the lone cruise ship present in the fiord at the time narrowly escaped the tsunami’s path, as it would have been catastrophic if in its trajectory. Shugar and Aram Fathian, a co-author of the study, emphasized the potential severity of the event, highlighting the risk posed to large vessels such as cruise ships.
The study also points out the significant retreat of the South Sawyer Glacier near the landslide site in the months leading up to the event, indicating that had the glacier not retreated, the landslide might have been averted or collapsed onto the glacier ice. Shugar attributes the glacier retreat and subsequent landslide to human-induced warming over the past two centuries, causing glaciers to thin and recede.
Despite the potential hazards posed by such events, Shugar does not advocate for barring cruise ships and tankers from the Canadian coast but suggests a thorough risk assessment and investment in early-warning systems. Fathian highlighted the importance of seismic activity monitoring for future prediction and early warnings, emphasizing the need for policymakers to adopt a national approach to evaluate and mitigate the risks associated with fiord tsunamis.