When supercooled, water can remain a liquid even below its freezing point. As explained in this Minute Physics video, this happens because of a tug-of-war between effects in the water. Generally speaking, having impurities in the water or smacking the bottle will shift that battle enough for freezing to win out. But it’s possible–theoretically, at least–to create a situation where supercooled water can never freeze. (Video and image credit: Minute Physics)
Frost forms hexagonal columns on a wooden rail in this microphotograph by Gregory B. Murray. Like in snowflakes, when water molecules freeze they position themselves to form six-sided crystals. From this perspective, it looks like a miniature version of the Giant’s Causeway. (Image credit: G. Murray; via Ars Technica)
Sea ice’s high reflectivity allows it to bounce solar rays away rather than absorb them, but melting ice exposes open waters, which are better at absorbing heat and thus lead to even more melting. To understand how changing sea ice affects climate, researchers need to tease out the mechanisms that affect sea ice over its lifetime. A new study does just that, showing that sea ice loses salt as it ages, in a process that makes it less porous.
Researchers built a tank that mimicked sea ice by holding one wall at a temperature below freezing and the opposite wall at a constant, above-freezing temperature. Over the first three days, ice formed rapidly on the cold wall. But it did not simply sit there, once formed. Instead, the researchers noticed the ice changing shape while maintaining the same average thickness. The ice got more transparent over time, too, indicating that it was losing its pores.
Looking closer, the team realized that the aging ice was slowly losing its salt. As the water froze, it pushed salt into liquid-filled pores in the ice. One wall of the pore was always colder than the others, causing ice to continue freezing there, while the opposite wall melted. Over time, this meant that every pore slowly migrated toward the warm side of the ice. Once the pore reached the surface, the briny liquid inside was released into the water and the ice left behind had one fewer pores. Repeated over and over, the ice eventually lost all its pores. (Image credit: T. Haaja; research credit and illustration: Y. Du et al.; via APS)
In “Lively,” filmmaker Christopher Dormoy zooms in on ice. He shows ice forming and melting, capturing bubbles and their trails, as well as the subtle flows that go on in and around the ice. By introducing blue dye, he highlights some of the internal flows we would otherwise miss. (Video and image credit: C. Dormoy)
On lake bottoms, decaying matter produces methane and other gases that get caught as bubbles when the water freezes. In liquid form, water is excellent at dissolving gases, but they come out of solution when the molecules freeze. In the arctic, these bubbles form wild, layered patterns like these captured by photographer Jan Erik Waider in a lake on the edge of Iceland’s Skaftafellsjökull glacier. Unlike the bubbles that form in our fridges’ icemakers, these bubbles are large enough that they take on complicated shapes. I especially love the ones that leave a visible trail of where the bubble shifted during the freezing process. (Image credit: J. Waider; via Colossal)
So many natural processes take place right in front of us, but they’re too small and too fast to see. Here, the Beauty of Science team puts some of those processes — crystallizing solids, nucleating bubbles, and more — front and center. The shapes and colors draw you in, inviting you to engage with science we see daily but rarely appreciate. (Video and image credit: Beauty of Science)
At times altocumulus cloud cover is pierced by circular or elongated holes, filled only with the wispiest of virga. These odd holes are known by many names: cavum, fallstreak holes, and hole punch clouds. Long-running debates about these clouds’ origins were put to rest some 14 years ago, after scientists showed they were triggered by airplanes passing through layers of supercooled droplets.
When supercooled, water droplets hang in the air without freezing, even though they are colder than the freezing point. This typically happens when the water is too pure to provide the specks of dust or biomass needed to form the nucleus of an ice crystal. But when an airplane passes through, the air accelerated over its wings gets even colder, dropping the temperature another 20 degrees Celsius. That is cold enough that, even without a nucleus, water drops will freeze. More and more ice crystals will form, until they grow heavy enough to fall, leaving behind a clear hole or wisps of falling precipitation.
In the satellite image above, flights moving in and out of Miami International Airport have left a variety of holes in the cloud cover each of them large enough to see from space! (Image credit: M. Garrison; research credit: A. Heymsfield et al. 2010 and A. Heymsfield et al. 2011; via NASA Earth Observatory)
If you’ve ever made ice in a freezer, you’ve probably noticed the streaks of frozen bubbles inside the ice. In its liquid state, water is good at dissolving various gases — like the carbon dioxide in sparkling water. During freezing, though, those gases cannot remain in solution; the water simply doesn’t have space between its crystalline ice lattice for non-water molecules. So the gases are forced out of solution, where they form bubbles. The final shape of the frozen bubble depends on the interplay between the speed of a bubble’s growth and how quickly the ice freezes. Here, the researchers used polarized light to outline the bubbles in color, highlighting the wide array of possible shapes. (Image credit: J. Meijer and D. Lohse; via GoSM)
Condensation forms beads of water on a surface. When suddenly cooled, those drops begin to freeze into frost. This video looks at the process in optical and in infrared, revealing the patterns of spreading frost and the tiny ice bridges that link one freezing drop to the next. (Video and image credit: D. Paulovics et al.)
Little by little, snow and ice transform the landscape in Jamie Scott’s film “Winter.” From individual snowflakes to entire forest vistas, the timelapses showcase how winter remakes every surface in its image. The growing icicles show freezing in action, but I especially love seeing the “flow” brought about by progressively greater snowfall. Tree limbs bow, shrubs swell, and riverbanks contract as the snow gets thicker. And that final shot that pulls out from single snowflakes to the entire forest? Stunning! (Video and image credit: J. Scott et al.; via Colossal)