Climate change could create mega tsunamis

Climate change could trigger giant tsunamis in the Southern Ocean by driving underwater landslides in Antarctica.

Simulation of a tsunami about to hit the beach. Photo: iStock — Simulation of a tsunami about to hit the beach. Photo: *iStock*

By drilling sediment cores hundreds of meters below the Antarctic seafloor, scientists discovered that during a previous period of global warming, between 3 and 15 million years ago, loose sediments formed and eroded, creating mega-tsunami waves that swept across the coasts of South America, New Zealand and Southeast Asia. As climate change warms the oceans, the team believes that such tsunamis are likely to occur again. They published their research results in the journal Nature Communications, Live Science reported on May 24.

"Undersea landslides are a major geological hazard with the potential to trigger tsunamis leading to serious loss of life," said Jenny Gales, a lecturer in hydrology and ocean exploration at the University of Plymouth, UK.

Researchers first found evidence of an ancient landslide off Antarctica in 2017 in the eastern Ross Sea. Trapped beneath the landslide were layers of weak sediment packed with fossils of marine life like phytoplankton. They returned to the area in 2018 and drilled deep into the seafloor to collect sediment cores, long columns of the Earth’s crust that can reveal the region’s geological history layer by layer.

By analyzing the sediment cores, the team found that the weak sediment layer formed during two periods, 3 million years ago in the mid-Pliocene and 15 million years ago in the Miocene. At that time, the waters around Antarctica were 3 degrees Celsius warmer than today, leading to algae blooms. After they died, they filled the seafloor below with fertile, slippery sediment, making the area vulnerable to landslides. During the colder climates and ice ages that followed, the sediment was buried under a thick layer of coarse gravel brought by glaciers and icebergs, said Robert McKay, director of the Antarctic Research Center at the University of Wellington.

Researchers aren’t sure what drove past submarine landslides in the area, but they speculate that the most likely cause was the melting of glaciers due to a warming climate. The end of the ice age caused ice sheets to shrink and recede, reducing pressure on Earth’s tectonic plates, causing them to bounce back in a process called isostatic rebound.

After enough weak sediments had accumulated, the movement of the Antarctic continent caused earthquakes that caused the coarse gravel layer above the sediment to slide off the edge of the continental shelf, leading to landslides and tsunamis. The extent of the ancient tsunamis is unclear, but scientists have documented two recent underwater landslides that produced massive tsunamis that caused serious damage. The 13-meter-high Grand Banks tsunami in 1929 killed 28 people off the coast of Canada, and the 15-meter-high tsunami in Papua New Guinea killed 2,200 people.

With layers of sediment buried beneath the Antarctic seabed and glaciers above slowly melting, researchers warn landslides and tsunamis could recur in the future.

An Khang (According to Live Science )

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