6 Dec 2013

Hair Ice and Singing Lakes and Icebergs: Fabulous Ice Phenomena

Jan Thornhill
Hair ice can grow 5 cm long
Hair ice growing from twig.

Antarctic sea ice from above
Antarctic sea ice (NASA)
My friend Ulli called one chilly morning a couple of weeks ago and said she’d found a stick in the woods for me. “A stick?” I said.

“You want it,” she said cryptically.

She was right. Though what she brought over ten minutes later looked like an ordinary piece of a dead alder branch, part of it was not ordinary in the least. One end had sprouted a glorious tuft of long silky white hair. Ulli had found hair ice!

Hair ice melting
Hair ice starting to melt. (Jan Thornhill)
Though you might think at first glance that hair ice is some kind of peculiar frost – it’s not. Frost forms when moisture in the air freezes on objects. Hair ice, on the other hand, starts from the inside and moves outwards. Moisture in a stick or twig is exuded through minute pores on the surface, and when this moisture hits humid sub-zero air the result is very fine filaments of ice that can grow up to five centimeters in length – filaments that look just like hair. It’s an uncommon phenomenon, and not just because weather conditions must be absolutely perfect. Here's the real glitch: the appearance of hair ice seems to be dependent on, of all things, fungi.

Hair Ice and Fungi

So what do fungi have to do with it? The idea that “a fungus participates in a decisive way” in the formation of hair ice, was first suggested in 1918 by the brilliant interdisciplinary scientist Alfred Wegener (who developed the theory of continental drift), but was unproven. Recently though, Gerhart Wagner and Christian Mätzler from the University of Bern have been studying "haareis" and its relationship to fungi. In one experiment they collected a number of twigs that had previously grown hair ice and treated them variously with three agents known to suppress the growth of fungi – heat, alcohol, and fungicide – while keeping a portion of each twig aside as a control. Afterwards, they froze all the samples under identical conditions, then compared the results. Sure enough, only the untreated pieces re-grew luxuriant manes of ice. 

The two scientists theorize that the living mycelium of various fungi within the wood (i.e. Exidia glandulosa or Tremella mesenterica) continues to metabolize at near freezing temperatures, producing heat and gases that force moisture outwards. When this moisture escapes through pores and comes into contact with humid below-freezing air, hair ice grows.

2cm long hair ice
Hair ice that grew overnight. (Jan Thornhill)
After reading about Wagner and Måtzler's success at coaxing hair ice to grow in the laboratory, I decided to try to try a simple experiment of my own. I soaked the stick Ulli had brought me in water (its original hair ice having quickly melted). I then laid it on a wet paper towel on a plate and put it out in our unheated boot room, then waited for the temperature to drop. By the 10:00 pm the whole stick was sprouting hair ice. By morning I had a new pet!

hair ice and ice globules
The end of the twig  formed solid globules of ice, possibly
because moisture was released too quickly to form hair ice. (Jan Thornhill) 

Singing Lakes

A few days later, another friend was talking about how much he loves the quality of the human voice outside on cold winter days. The topic of walking on frozen lakes came up. I asked if he’d ever heard a frozen lake “sing.”

person walking on frozen lake
Frozen lakes sing! (Nentori)
I’ve heard it several times – haunting, otherworldly sounds caused by ice expanding and contracting, which is most common when there are major fluctuations in temperature. The best sounds, and the ones that carry the furthest, occur when there is no snow cover – rare conditions on the lakes near where I live, but not unheard of. Listen to Andreas Bick’s extraordinary recording of this phenomenon on a lake in Germany here. Turn up the volume and brace yourself!

Antarctic Ice & Animal Sounds

Weddell seals underwater
Weddell seals whistle and chirp.
And then I discovered something even more wonderful: The Alfred Wegener Institute (yes! that's the same Alfred Wegener as mentioned above!) that co-ordinates German polar research in both the Arctic and Antarctic has an acoustic laboratory in Antarctica. They are always recording – and on their website they offer this MP3 audio livestream of Antarctic ice and animal sounds from near the Neumayer Station on the ice shelf of Atka Bay. You can listen to the under-ice sounds of the Antarctic in real time! I can't turn it off!

All of this icy stuff is so cool it warms my heart. 

More Links:

This page from the Alfred Wegener Institute has sound files of various seal and whale noises to listen for on the live audio feed, as well as rubbing ice, singing icebergs, and some “mystery” sounds that are truly astonishing.

Download Gerhart Wagner and Christian Mätzler"s paper,  "Haareis auf morschem Laubholz als biophysickalisches Phanomen"  or  "Hair Ice of Rotten Wood of Broadleaf Trees – A Biophysical Phenomenon" – lots of pictures, though only some parts are in English.

Weddell seals source: http://commons.wikimedia.org/wiki/File:Diving_weddell_seals.jpg

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