Researchers at NYU’s Courant Institute of Mathematical Sciences found that icebergs capsize because of the unstable shapes they melt into, further defining the fluid dynamics behind how global warming affects major bodies of water.
In an article published last month, Courant researchers described how they modeled the hydrodynamics behind icebergs capsizing. The team found that when ice floats in water, the part that sits in the water melts faster than the top half because of water pressure and buoyancy, causing it to form strange shapes and capsize.
“All we do is put a piece of ice in the tank and by itself, and it starts capsizing,” said Alison Kim, a contributing researcher and fourth-year Ph.D. student. “It’s catastrophic, because they’re so huge and can cause tsunamis and break up other icebergs.
The team prepared ice blocks as cylinders and placed them in room temperature water. They documented the ice melting in a video and used the footage to draft mathematical models based on the shape the ice melted into and how frequently it capsized.
Bobae Johnson, a contributing researcher and Courant Ph.D. candidate, said that ice repeatedly moved around when placed in water, meaning they had to devise a way for the ice to remain in place without manipulation so they could assess its natural melting process. They also needed special lighting, and for the ice to be perfectly clear — which required freezing the ice from the bottom up.
“It was something that seemed really simple but we had to approach it from so many directions,” Johnson said. “We had the complexities of running experiments, and then we had to analyze a lot of data from our experiments — then we had to approach it from the completely opposite direction and try to use math to model what was happening.”
In a study supported by a grant from the National Science Foundation, the team was originally observing how ice melts by holding it underwater — until a piece broke loose and floated to the top. They watched as the ice block took different forms and capsized around a dozen times in a half an hour, which inspired them to change the course of the experiment.
The researchers hoped that by learning about the physics behind how ice melts, they can add value to climate models and help other scientists better understand the implications of global warming.
“Our results show that math modeling at a small scale is really important because there’s so much we don’t understand on a small scale,” Johnson said. “In order to scale up to bigger things that involve the climate, we need to have foundational understanding of the basics of how ice melts.”
Lead author and Courant professor Leif Ristroph said that going forward, he hopes to expand research on how ice changes shapes according to its environment. He said that one topic he’s particularly interested in is documenting the way that asymmetric shapes propel ice forward and cause it to gradually move.
“Ice has been a really fruitful problem,” Ristroph said. “Once we have it and start to play with it — and you have an open mind as an experimentalist who’s tinkering with it — it dances for you, it rolls over for you and does all the fun pet tricks that you would want it to do.”
Contact Ashlie West at [email protected].