Scientists on a research ship in Antarctica watched the front of a glacier disintegrate and his measurements “went off scale”.
In addition to witnessing disruptions to the ocean surface, they recorded tsunamis “internal” submarines as tall as a house, orA phenomenon that had previously been overlooked in understanding ocean mixing and in computer models.
The team, led by researchers from the British Antarctic Survey (BAS), is now reporting their observations in the journal Science Advances.
Internal tsunamis are an important factor in the mixing of the oceans, which affects life in the ocean, temperatures at different depths and the amount of ice that the ocean can melt. Ice in Antarctica flows to the coast along valleys filled with glaciers. As some of the ice melts into the ocean, much of it breaks up into icebergsranging in size from small chunks to the size of a country.
A team aboard the BAS research vessel RRS James Clark Ross was taking oceanic measurements near the William Glacier on the Antarctic Peninsula when its front dramatically disintegrated into thousands of tiny pieces.
William Glacier typically has one or two large calving events per year, and the team estimated that around 78,000 square meters of ice broke off, around the area of 10 football fields, with the glacier front rising 40 meters. above sea level.
Before it ruptured, the water temperature was coldest at about 50-100 meters depth and warmest below it. After calving this changed dramatically, with much more uniform temperatures at different depths.
The lead author of the study, Professor Michael Meredith, head of the polar oceans team at BAS, said in a statement: “This was remarkable to see, and we were lucky to be in the right place at the right time. Many glaciers end in the sea, and their ends regularly break up into icebergs. This can cause large waves on the surface, but we now know that it also creates waves within the ocean. When they break, 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. This is important for us to understand better.
“The mix influences where are the nutrients in the water and that is important for ecosystems and biodiversity. We thought we knew what was causing this mix; In summer, we thought it was mainly wind and tides, but it never occurred to us that calving icebergs could cause internal tsunamis that would mix things up so substantially.”
Internal tsunamis have been noted in a handful of locations, caused by landslides. Until now, no one has realized they are happening around Antarctica, probably all the time because of the thousands of glaciers calving there. Other places with glaciers are also likely to be affected, such as Greenland and other parts of the Arctic.
This serendipitous observation and understanding is important, as Glaciers retreat and crumble further as global warming continues. This could likely increase the number of internal tsunamis created and the mix they cause.
This process is not accounted for in current computer models, allowing us to predict what might happen in Antarctica. This discovery changes our understanding of how the ocean around Antarctica mixes and will improve understanding of what it means for climate, ecosystems and sea level rise.
Professor Meredith commented: “Our serendipitous timing shows how much more we need to learn about these remote environments and how important they are to our planet.”