Researchers have found that collapsing blocks of ice in Antarctica cause not only a surface tsunami, but also a second tsunami at depth. This event has significant impacts on water temperature and underwater biodiversity.
At the poles, the collapse of sea ice apparently causes severe turbulence in the water, in the form of massive waves resembling a real tsunami. However, scientists have made an additional discovery: in addition to the tsunami at the water surface, the falling ice causes a second tsunami at depth.
From a distant perspective like ours, this “detail” doesn’t seem to matter. However, this double tsunami affects the composition of the ocean by mixing several masses of water. According to the European Space Agency, which published the abstract of a study, a British research team was on board a boat in the Antarctic Peninsula in January 2020 when a piece of Glacier William collapsed in front of them.
At the same time, a Copernicus Sentinel-1 satellite took a picture of the event. This showed the different distribution of ice and water between January 8 (before the collapse) and January 20 (the day of the collapse). This collapse caused the detachment of a block of 78,000 m2, the equivalent of 10 football fields, knowing that William Glacier has already lost 3 km of ice since 1955.
The collapse of part of William Glacier in Antarctica filmed in 2020. © European Space Agency
Underwater tsunami changes sea temperature
The research team then witnessed the tsunami that hit the sea surface, but were also able to record the second tsunami underwater using sensors. A phenomenon that is very important in climate forecasting models and has never been discovered before.
The chaos caused by the underwater tsunami has several consequences: due to the mixing of water masses that should not meet, the underwater waves, which can reach more than 10 meters, have an impact on wildlife, underwater temperatures at different depths and thereby on melting ice. Once the pieces of ice have detached from their main block, icebergs are most often formed. But some of them sink into the ocean and melt.
Before the glacier collapsed, the sea water was cold at a depth of 50-100 m, with a warmer water layer below. After the submarine tsunami, the mixing of the water resulted in a much more uniform temperature between these different bodies of water. The nutrients available in the ocean, which nourish biodiversity, are distributed in the water layers according to the different temperatures. By mixing these layers and unifying the temperatures, the ice collapse then affects the entire ocean ecosystem and thus biodiversity.
A parameter that can be used to indicate the results of climate forecasts
In general, these water mixtures are mainly formed at the surface under the action of wind and tides. But the collapse of the ice linked to global warming is causing a violent mixing of water at depth, of the same kind as in an earthquake or a landslide, specifies the European Space Agency.
So far, these sudden mixings caused by melting ice have only been observed in Antarctica, but scientists believe they may also occur in Greenland and the Arctic. An important parameter that must be taken into account in the development of future climate and the consequences of global warming and is currently not yet integrated into climate prediction models.
This discovery must therefore be included in the calculations of new climate models, the purpose of which is to stimulate the climate of the coming years. The integration of this parameter will thus make it possible to obtain more precise results on the development of sea level rise, on the future composition of marine ecosystems and on global warming of the planet.
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