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IMAGE: Visualization of the coupling dynamics of the ice layer and turbulent convective motions in the water layer. 3D simulation for the surface below 8oC and the upper surface in … view More
Credit: Chao Sun
VIRTUAL MEETING (CST), November 22, 2020 – Eric Hester has spent the past three years hunting for icebergs. A graduate student in mathematics at the University of Sydney in Australia, Hester and researchers from the Woods Hole Oceanographic Institution in Massachusetts are studying how the shape of an iceberg shapes the way it melts.
“Ice deforms when it melts,” said physical oceanographer Claudia Cenedese, who worked with Hester on the project. “It makes these shapes very strange, especially on the bottom, like the way the wind shapes a mountain on a longer time scale.”
At the 73rd Annual Meeting of the American Physical Society’s Division of Fluid Dynamics, Hester presented the results of her group’s experiments aimed at understanding how melting alters the shifting boundary of a shrinking iceberg and how these alterations in turn affect the dissolution.
The dynamics of iceberg melting are not present in most climate models, Cendese said. Including them could help with the prediction: Icebergs pump fresh water from ice sheets into the oceans, strengthening communities of living organisms. Icebergs are the main source of freshwater in the Greenland fjords and contribute significantly to the loss of freshwater in Antarctica. Icebergs play a vital role in climate, Cenedese said, and shouldn’t be overlooked in models. The physics of melting ice are well understood and some models accurately simulate it, he said. Others don’t. “But what you can’t do in those simulations is change the shape of the ice.”
Icebergs form in a wide range of shapes and sizes, Hester said, and distinct thermodynamic processes affect different surfaces. The base, immersed in water, does not melt in the same way as the side. “And every face doesn’t melt evenly,” Cenedese added.
Hester conducted her experiments by immersing a block of colored ice in a channel with a controlled flow of flowing water and watching it melt. He and his colleagues found that the side facing a current melts faster than the sides that run parallel to the flow. Combining experimental and numerical approaches, Hester and his collaborators traced the relative influences of factors such as the relative speed of water and proportions, or the proportion of height and width on one side. Unsurprisingly, they found that the bottom had the lowest melting rate.
Cenedese said Hester’s project brings together collaborators from a wide range of disciplines and countries and that diverse collaboration was needed for such an interdisciplinary project. “Working in isolation isn’t that productive in this case.”
Other studies discussed at the conference focused on ice formation rather than melting. During a session on particle-laden flows, engineer Jiarong Hong of the St. Anthony Falls Laboratory at the University of Minnesota, Minneapolis, discussed the results of experiments showing how turbulence affects both the speed and distribution of snow. as it falls and settles. The findings could also help scientists better understand precipitation, Hong said.
Another project, presented by physicist Chao Sun of Tsinghua University in China and his group during a session on convection and buoyancy-guided flows, focused on ice formation in lakes.
Working on a scholarship from the Natural Science Foundation of China with Ziqi Wang of Tsinghua University, Enrico Calzavarini of the University of Lille in France, and Federico Toschi of the Eindhoven University of Technology in the Netherlands, Sun showed how the formation of the ice on a lake is closely related to the fluid dynamics of the underlying water.
A lake can have layers of water of different densities and temperatures. “Water density anomalies can induce elaborate fluid dynamics under a moving ice front and can drastically change system behaviors,” Sun said. “This has often been ignored in previous studies.”
Sun’s team combined physical experiments, numerical simulations, and theoretical models to study the connection between ice and convective (turbulent) flows. They identified four distinct regimes of different flow dynamics, each interacting with other layers and ice in its own way. Even with that complexity, however, the group developed an accurate theoretical model that could be used in future studies.
“It made a correct prediction of the thickness of the ice sheet and the time of ice formation,” Sun said.
Since ice formation and melting plays such a critical role in climate, he said, a better understanding of the fluid dynamics behind the process could help researchers accurately identify and study markers of a warming world. “The time when ice forms and melts, for example, could potentially provide an indicator of climate change.”
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ABSTRACTS HIGHLIGHT
How does the shape of the iceberg affect the melt?
MANIFEST:
8:45 am CST, Tuesday, November 24, 2020
ABSTRACT:
http: // meetings.
CONTACT:
Eric Hester,
[email protected]
Settlement dynamics of snow in atmospheric turbulence
MANIFEST:
5:00 p.m. CST, Monday November 23, 2020
ABSTRACT:
https: /
CONTACT:
Jiarong Hong,
[email protected]
How lake ice growth depends on the underlying fluid dynamics
MANIFEST:
3:55 PM CST, Sunday November 22, 2020
ABSTRACT:
http: // meetings.
CONTACT:
Chao Sun,
[email protected]
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Registration:
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ABOUT DFD
The Fluid Dynamics Division of the American Physical Society, founded in 1947, exists for the advancement and dissemination of knowledge of the physics of fluids with particular emphasis on the dynamic theories of the liquid, plastic and gaseous states of matter in all conditions of temperature and pressure. .
ABOUT APS
The American Physical Society (APS) is a nonprofit membership organization that works to advance and disseminate knowledge of physics through its outstanding research journals, scientific meetings, and educational, outreach, support and international activities. APS represents over 55,000 members, including physicists from academia, national laboratories, and industry in the United States and around the world. The company’s offices are located in College Park, Maryland (headquarters), Ridge, New York and Washington, DC.
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