When you get outside in winter, it's an opportunity to observe some natural wonders, and Something Wild listeners have questions!
Casey asks: When I went outside this morning, I saw that everything was covered in very spiky frost, a gravity-defying frost on every surface. I’m wondering, how does that happen? How does that kind of frost form?
The quick answer: it’s rime ice.
Rime ice often forms when it is foggy and there is a lot of moisture in the air. Supercooled fog droplets freeze on contact with cold tree branches, power lines, and buildings.
And it’s not the clear glaze we normally think of with ice. Rime ice is white due to the air trapped in the freezing fog droplets that make it opaque.
You can often see rime ice on the summit of Mt. Washington, because in the winter the summit is frequently in the clouds and fog with below-freezing temperatures.
Mike Carman of the Mt. Washington Observatory says high winds tend to deposit rime ice much faster, resulting in feathers that are sometimes many feet in length forming on all summit structures.
Something Wild host Grace McCulloch says, “I was at Lake of the Clouds recently and got to see rime ice up close. It’s beautiful, and it works like a natural weather vane, showing you where the wind was blowing when it developed.”
Have you ever been out for a walk and come back with your breath frozen onto your eyelashes, eyebrows, and facial hair? Rime ice can even form on animal fur and human hair.
Hoar frost is another type of ice, with a much more feathered and delicate look. It happens on clear, cold nights when moisture in the air near the ground cools and changes directly from water vapor to ice.
Here’s another question from a listener:
Emily in Hillsboro: My question has to do with snow fleas. I know that they’re generally found in the soil so we don’t see them the rest of the year, but my question is: why do they come to the top of the snow? And usually I see them in the late spring, in hollows and near trees, but this year, I saw them the first cold snow we had, and I was wondering why they’re in specific spots.
Snow fleas, which aren’t actually fleas, are also known as springtails. They get their name from a body part called a furcula that’s like a spring under the abdomen. When released, it propels the snow flea upwards and away from potential enemies.
They are ancient creatures, thought to be among the first arthropods to move from water to land. They’ve been found in deep caves (6,500 feet underground) as well as Mount Everest. With six legs they are still considered to be hexapods. They are, however, not true insects. They are arthropods, in the same group as spiders, crabs, lobsters, and insects.
You may know that some frogs and turtles can overwinter without their cells freezing, thanks to a biological antifreeze in their blood. Springtails use a different antifreeze protein that lowers the freezing point of their bodily fluids. They can remain active even in sub-zero temperatures, allowing them to break down organic matter and bacteria year-round.
Their antifreeze proteins are structurally unique, suggesting their adaptation evolved independently. Researchers are even studying them for potential use in preserving human organs for transplant longer and at colder temperatures.
Springtails are triggered to feed on microscopic fungi, algae, and decaying organic material exposed by melting snow on the surface. Warmer, sunny days, even in winter, allow them to move and find food more easily. Large populations may cause them to seek out new areas or food.
They are especially drawn to damp areas with organic debris. Around trees is common, where there is shelter, moisture, and an easy pathway up from the soil.
And another reason they’re found in large numbers is reproduction. Fertile females release a sex-pheromone that attracts other springtails, and the bigger the gathering, the stronger the signal. That’s why you see so many of them.
If you have a question for Something Wild, email or send a voice memo to SomethingWild @NHPR.org.
Something Wild is a collaboration between the Forest Society, NH Audubon and NHPR.
