Climate change could unleash massive tsunamis in the Antarctic Ocean triggered by submarine landslides. A new study based on sediment drilling on the Antarctic seafloor predicts this alarming possibility. The scientists’ hypotheses are supported by past events. During previous periods of global warming, 3 million and 15 million years ago, loose sediment layers slid into the sea, creating tsunamis that hit the coasts of South America, New Zealand, and Southeast Asia.
Today, with the anthropogenic warming of the oceans, researchers believe that there is a real possibility that these tsunamis could be unleashed once again. Their findings were published on May 18th in the journal Nature Communications (ref.).
Instability of Antarctica
“Submarine landslides pose a significant risk. They have the potential to trigger enormous tsunamis that can lead to loss of human lives” stated Jenny Gales, a lecturer in hydrography and ocean exploration at the University of Plymouth in the United Kingdom. “Our results highlight the urgent need to improve our understanding of these phenomena. We need to understand how global climate change affects the stability of these regions”.
In 2017, researchers found evidence of ancient landslides off Antarctica for the first time in the Eastern Ross Sea. Trapped beneath these landslides, within layers of sediment, are fossilized marine creatures known as phytoplankton. Scientists returned to the site a year later and drilled deep into the seafloor to uncover the region’s geological history.
By analyzing sediment cores, scientists learned that the weak sediment layers formed during two periods. The first occurred approximately 3 million years ago during the warm mid-Pliocene, and the other 15 million years ago during the Miocene. During these epochs, the waters of Antarctica were 3 degrees Celsius warmer than today’s temperatures. Algal blooms filled the underlying seafloor, creating a rich and slippery sediment, making the region prone to landslides.
“During subsequent cold climates and ice ages, these slippery layers were covered by thick layers of coarse gravel produced by glaciers and icebergs” said Robert McKay, director of the Antarctic Research Center at Victoria University in Wellington.
Causes of tsunamis
The exact triggering factor of past submarine landslides in the region is not precisely known. Researchers believe that the most likely culprit is glacier melting due to climate warming. The end of glacial periods on Earth caused the shrinking and retreat of ice caps. By lightening the load on the tectonic plates, they bounced upward in a process known as isostatic rebound.
After sufficient amounts of weak sediment layers had accumulated, the continental uplift of Antarctica triggered earthquakes that caused the coarse gravel to slide over the slippery layers from the edge of the continental shelf, triggering landslides that unleashed enormous tsunamis.
The scale and size of the ancient oceanic tsunamis are not known. However, based on two relatively recent submarine landslides, scientists have understood the magnitude of these potential destructive events. The 1929 Grand Banks tsunami generated waves as high as 13 meters. Meanwhile, the 1998 Papua New Guinea tsunami unleashed waves as high as 15 meters, resulting in 2,200 casualties.
Current situation
With many layers of sediment buried beneath the Antarctic seafloor and the melting of glaciers on top of the continent due to climate change, researchers warn that if they are correct, future landslides and massive tsunamis could happen again. “The same layers are still present on the outer continental shelf. So it is highly likely that these landslides will occur. The big question is whether the triggering factor of the events is still in play” McKay stated.
“We have proposed isostatic rebound as a potential logical trigger. But sediment erosion could be caused by a random fault or climate-driven changes in ocean currents at key points on the continental shelf. We will know more when we can use computational models in future studies”.