The front of Antarctic glaciers that flow towards the coast breaks off due to melting, creating icebergs. These are known as fragmentation events and can have dramatic consequences. Not only are large chunks of ice free to move and reach lower latitudes, the process can also create a powerful underwater tsunami that profoundly alters the ocean.

The underwater tsunami phenomenon is a recent discovery. It’s invisible in the sense that it doesn’t create massive wave fronts, but it can still move a significant amount of water. Internal tsunamis can happen in oceans and lakes without being visible on the surface.

The latest study was carried out by a team on board the RRS James Clark Ross research vessel, part of the British Antarctic Survey (BAS) fleet. Scientists were taking measurements of the ocean near William Glacier and witnessed the entire front shattering into a multitude of pieces.

How is an underwater tsunami formed?

The front of the glacier was up to 40 meters above sea level, and the amount of ice that broke off had an area of ​​78,000 square meters. It may not seem like much, but it generated an internal tsunami with underwater waves as high as a house.

“It was remarkable to see and we were lucky to be in the right place at the right time. Many glaciers terminate in the sea, and icebergs regularly break off from their extremities. This can cause large waves at the surface, but we now know it also creates waves in the ocean interior,” said Professor Michael Meredith, Head of the Polar Oceans Team at BAS and lead author of the study.

“When they break, these internal waves cause the sea to churn and this affects sea life, the temperature at different depths and the amount of ice that can melt. This is important for us to better understand what’s going on,” Meredith continued.

Much remains to be learned about the oceans

Ocean churning is a key process for distributing nutrients across vast bodies of water. It was thought to be caused mostly by wind and tides, but this paper suggests that the breaking up of icebergs that cause internal tsunamis also plays a role in the churning.

The team measured temperatures in the ocean and found that the tsunami evened out temperatures at different depths, they note IFL Science.

“Our fortuitous moment shows how much we still need to learn about these distant environments and how they matter to our planet,” Professor Meredith said.

The study is published in the journal Science Advances.

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