Researchers on board the British Antarctic Survey’s RRS James Clark Ross have captured a major calving event as the William Glacier disintegrated into a thousand small pieces before their very eyes. William Glacier lies on the Antarctic Peninsula.
While such events have long been known to trigger tsunamis at the surface of the ocean, the calving event when analysed by the team revealed that the glacier calving can excite vigorous internal waves – a process that has been neglected in driving ocean mixing in computer models.
The findings have been published in the journal Science Advances.
While the results have been released now, the event happened in 2020 when the team aboard the British Antarctic Survey’s RRS James Clark Ross research ship was taking ocean measurements off the Antarctic Peninsula. They watched the William Glacier disintegrate into a thousand small pieces before their very eyes.
The William Glacier typically has one or two large calving events a year. With the front of the glacier towering 40 m above sea level, the team estimated that this event broke off around 78,000 square meters of ice – around the area of 10 football pitches. Before the glacier front disintegrated, the ocean water at the depth of 50–100 m was cool but there was a warmer layer beneath this. After the calving, this changed dramatically, with the temperature much more even across different depths.
Researchers said that internal tsunami waves are an important factor in ocean mixing, which affects marine life, temperatures at different depths, and how much ice the ocean can melt. Researchers used the data from Europe’s Copernicus Sentinel-1 satellites passed overhead while the ship was close to the Peninsula and captured a radar image.
“This was remarkable to see, and we were lucky to be in the right place at the right time. Lots of glaciers end in the sea, and their fronts regularly split off into icebergs. This can cause big surface waves, but we know now that it also creates waves inside the ocean. These internal waves cause the sea to mix, and this affects life in the sea, how warm it is at different depths and how much ice it can melt,” Michael Meredith, lead author of the paper said.
Internal tsunamis have been noticed in a handful of places, caused by landslides. Until now, no one had noticed that they are happening around Antarctica, probably all the time because of the thousands of calving glaciers there. Other places with glaciers are also likely to be affected, including Greenland and elsewhere in the Arctic.
Glaciers around the world are generally retreating – a serious consequence of climate change.
