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Antarctica: Tsunamis – triggered by calving glaciers


Huge masses of ice break off from glaciers several times a year and fall into the sea. According to a study, this mixes up the water – with significant effects. For plankton, however, this is good news.

Enlarge image

William Glacier (Image from 2017)

Photo: Eleanor Scriven / robertharding / IMAGO

About once or twice a year, larger ice masses from the William Glacier on the Antarctic Peninsula fall into the water.

This also happened in January 2020 - when the RSS James Clark Ross was nearby, which was carrying out oceanographic measurements in the Börgenbuch.

The researchers were able to determine that the so-called calving of the glacier triggers tsunamis under water, which mix the water vigorously.

The results of the research were published in the journal Science Advances, reported by Spektrum.

In the case of internal tsunamis, as the scientists write, the energy is not discharged in large waves on the surface, which are particularly dangerous when they hit inhabited land.

Instead, the energy goes downwards - and here it ensures that the water levels are mixed.

Because these tsunamis are widespread and occur frequently, they are at least comparable to winds and much more important than tides for the regional mixing of the shelf, the study says.

They could also be relevant in Greenland and in the Arctic.

The frequency of calving may also change with higher sea temperatures, suggesting a possible shift in internal tsunami genesis and mixing to a warmer climate, the authors write.

Before calving, there had been a pronounced subsurface temperature minimum in the Börgenbucht, which is characteristic of the Southern Ocean in summer.

In the vicinity of the William Glacier, however, this is also related to the underground spread of glacial meltwater.

Below, waters coming in from the coast provided the heat for the melting of the glacier.

After calving, the structure of the water column differed significantly - it was much more homogeneous.

According to the researchers, the changes in the water of the Antarctic continental shelf have a global climatic influence.

The heat from these waters is driving the retreat of glaciers and ice shelves on the fringes of Antarctica, affecting ice sheet stability and sea-level rise.

However, the strong mixing at the interface between the ocean and the ice would also ensure that the nutrients were distributed differently in the water - and were therefore also accessible to plankton in the upper layer of the water.

According to the information, the William Glacier is about 4.5 kilometers wide.

According to the study, the calving extended over about one kilometer of the ice front, and 78,000 square meters of ice had drained.

The event is characteristic of the disintegration of the ice front.


Source: spiegel

All tech articles on 2022-11-29

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