Climate change could unleash gigantic tsunamis within the Southern Ocean by triggering underwater landslides in Antarctica, a brand new study warns.
By drilling into sediment cores lots of of feet beneath the seafloor in Antarctica, scientists discovered that in previous periods of worldwide warming — 3 million and 15 million years ago — loose sediment layers formed and slipped to send massive tsunami waves racing to the shores of South America, Recent Zealand and Southeast Asia.
And as climate change heats the oceans, the researchers think there is a possibility these tsunamis could possibly be unleashed over again. Their findings were published May 18 within the journal Nature Communications.
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“Submarine landslides are a significant geohazard with the potential to trigger tsunamis that may lead to very large lack of life,” Jenny Gales, a lecturer in hydrography and ocean exploration on the University of Plymouth within the U.K., said in an announcement. “Our findings highlight how we urgently need to reinforce our understanding of how global climate change might influence the steadiness of those regions and potential for future tsunamis.”
Researchers first found evidence of ancient landslides off Antarctica in 2017 within the eastern Ross Sea. Trapped underneath these landslides are layers of weak sediment filled with fossilized sea creatures often called phytoplankton.
Scientists returned to the world in 2018 and drilled deep into the seafloor to extract sediment cores — long, thin cylinders of the Earth’s crust that show, layer by layer, the geological history of the region.
By analyzing the sediment cores, the scientists learned that the layers of weak sediment formed during two periods, one around 3 million years ago within the mid-Pliocene warm period, and the opposite roughly 15 million years ago through the Miocene climate optimum. During these epochs, the waters around Antarctica were 5.4 degrees Fahrenheit (3 degrees Celsius) warmer than today, resulting in bursts of algal blooms that, after that they had died, filled the seafloor below with a wealthy and slippery sediment — making the region susceptible to landslides.
“During subsequent cold climates and ice ages these slippery layers were overlain by thick layers of coarse gravel delivered by glaciers and icebergs,” Robert McKay, director of the Antarctic Research Centre at Victoria University of Wellington and co-chief scientist of International Ocean Discovery Program Expedition 374 — which extracted the sediment cores in 2018 — told Live Science in an email.
The precise trigger for the region’s past underwater landslides isn’t known of course, however the researchers have found a most-likely offender: the melting of glacier ice by a warming climate. The ending of Earth’s periodic glacial periods caused ice sheets to shrink and recede, lightening the load on Earth’s tectonic plates and making them rebound upwards in a process often called isostatic rebound.
After the layers of weak sediment had built up in sufficient quantities, Antarctica’s continental upspringing triggered earthquakes that caused the coarse gravel atop the slippery layers to slip off the continental shelf edge — causing landslides that unleashed tsunamis.
The size and size of the traditional ocean waves just isn’t known, however the scientists note two relatively recent submarine landslides that generated huge tsunamis and caused significant lack of life: The 1929 Grand Banks tsunami that generated 42-foot-high (13 meters) waves and killed around 28 people off Canada’s Newfoundland coast; and the 1998 Papua Recent Guinea tsunami that unleashed 49-foot-high (15 m) waves that claimed 2,200 lives.
With many layers of the sediment buried beneath the Antarctic seabed, and the glaciers on top of the landmass slowly melting away, the researchers warn that — in the event that they’re right that glacial melting caused them previously — future landslides, and tsunamis, could occur again.
“The identical layers are still present on the outer continental shelf — so it’s ‘primed’ for more of those slides to occur, but the massive query is whether or not the trigger for the events continues to be in play.” McKay said. “We proposed isostatic rebound as a logical potential trigger, but it surely could possibly be random failure, or climate regulated shifts in ocean currents acting to erode sediment at key locations on the continental shelf that might trigger slope failure. That is something we could use computer models to evaluate for in future studies.”
