Scientists warn giant tsunamis from Antarctica will come with global warming

Scientists discovered that, between 3 and 15 million years ago, in earlier times of global warming, layers of loose sedimentary rock shifted, causing massive tsunami waves that rushed to the coasts of South America, New Zealand and Southeast Asia. The same thing can happen again today.

what is known

Underwater landslides are an important geological hazard that can cause tsunamis that cause great human casualties. Our findings underscore our urgent need to deepen our understanding of how global climate change may affect the stability of these regions and the potential for future tsunamis.
– says Jenny Gales, a lecturer in hydrography and ocean studies at the University of Plymouth in Great Britain.

Researchers first found evidence of ancient landslides off the coast of Antarctica in the eastern part of the Ross Sea in 2017. Beneath these landslides are layers of weak sedimentary rock filled with fossilized sea creatures known as phytoplankton. In 2018, scientists returned to the area and drilled deep under the seafloor to extract sediment cores, which are long, thin cylinders of the earth’s crust that reveal the region’s geological history layer by layer.

After analyzing the sediment cores, the scientists learned that weak sediment layers were formed over two periods:

• About 3 million years ago, during the warm period of the middle Pliocene.
• About 15 million years ago, during the Miocene climatic optimum.

During these times, the waters around Antarctica were 3 degrees Celsius warmer than today, leading to algal bloom eruptions that, when they died, filled the seafloor below with rich and slippery sediment, making the area prone to landslides. In subsequent cold climatic periods and ice ages, these slippery layers were covered with thick layers of coarse gravel brought by glaciers and icebergs.

While the exact cause of underwater landslides that have occurred in the past in this region is not known for certain, researchers have identified the most likely culprit: melting of the ice sheet due to the warming climate. The end of Earth’s periodic ice ages caused ice sheets to contract and retreat, easing the load on Earth’s tectonic plates and causing them to retract upward in a process known as isostatic rebound.

After enough layers of weak sedimentary rock had accumulated, the uplift of Antarctica triggered earthquakes that led to landslides that caused coarse gravel to slide off the edge of the continental shelf over slippery layers and caused tsunamis.

The scale of the threat

The sizes of ancient ocean waves are unknown, but scientists point out two relatively recent underwater landslides that created massive tsunamis and caused significant human casualties:

• The 1929 Grand Banks Tsunami created waves 13 feet high and killed about 28 people off the coast of Newfoundland, Canada.
• The tsunami that struck Papua New Guinea in 1998, causing waves of 15 meters high, claimed 2,200 lives.

Researchers warn that future landslides and tsunamis may repeat themselves, as many layers of sedimentary rock still buried under Antarctica’s seabed and glaciers on land are slowly melting.