Thursday, February 11, 2016

Wacky Icicle Does Not Seem To Know About Gravity

One of the best things about doing this blog is the interesting pictures folks send me.   This week Anne Fox sent along a startling picture of some icicles from her cabin in Winthrop (see below).   This icicle curved upward and them curled around in a circle.   If you look carefully, there are a few more that had a similar behavior.

How could this be?  Icicles should be directed towards the ground as gravity acts on the melting water.!

I had my theory about this, but asked for more pictures with additional perspectives (see below).  Before the spoiler, think about this yourself.

My hypothesis.   Snow fell on the roof and temperatures starting to warm.  The snow started to flow slowly down and off the roof, with some icicles on below the leading edge as melted water refroze below.  Yes, icicles that WERE directed downward.  Naturally, the snow layer, under the influence of gravity, started to bend downwards as it extended off the roof.  Away from the relatively warm roof or because the exposure to the sun changed, the snow layer cooled and refroze, maintaining the curve.  As more snow pushed off the roof, the snow layer in the air below naturally had an increased curvature, causing the icicles on its leading edge to slow turn upward.   Perhaps because of warming air or because the icicle got close to the warmer post (darker colors absorb solar radiation better), the tip of the icicle started to curve downward, producing the strange curved tip.

Anyway, I am open to other explanations for these amazing pictures.    Could persistent wind contribute to curving?  Even aliens, if you can make that work.

This case of highly curved icicles, although unusual, is not unique.  Here is an example from a cabin near Truckee, CA:

Northwest Weather Workshop

The big local weather workshop is less than a month away (March 4-5, Seattle).  If you are interested in attending, the agenda and registration information can be found here.


SkunkBayWeather said...

Cliff… It’s simple… Obviously it’s all about global warming. Even our icicles are starting to look like desert climate scorpion tails…. :)

Unknown said...

Sort of reminds me of helictite in caves.

Kenna Wickman said...

Cliff, this is due to the influence of Gravity Waves, which they just discovered as real with the Laser Interferometer Gravitational-Wave Observatory (Ligo).

Ride the Waves and Let's Do the Time Warp Again!

Realm Lovejoy said...

I saw this happen with my candle. The wax was melting toward the direction of my fireplace so there was a horizontal wax stick coming out of the candle. I think it's the same with the icicles--it's melting gradually toward the hotter area, the cabin.

Richard Crutcher said...

The one big curved icicle probably began as melt water near the stovepipe that sticks through the roof directly above it. It's coincidental that it's above one of the porch posts. But the extra warmth of the post, or even that it may have eventually touched the post as the snow layer slipped off the metal roof, enhanced the curvature to make it curl back on itself. The remarkable thing to me is that the snow layer was strong enough to continue holding the heavy icicle up for as long as it must have taken for the whole effect to develop.

Michael Snyder said...

Larger amount of snow on roofs, icicles form on the overhangs, snow melts small amounts during the day and slides small amounts toward the edges. The icicles, in response, curve inwards toward the cabin as the snow creeps over the overhang. This happens all the time in the cascades at cabins up there. Have the icicle hit an object at the same time/ combine some melting and refreezing and all kinds of cool shapes can happen.

Nice pictures Cliff...

Deek said...

Cliff, Having watched this phenomenon much of the winter on our structures in Winthrop I have to agree with your hypothesis. We didn't get any curly shapes like those in the picture but we did get icicles pointing inward and even upwards a bit past horizontal. This even happened on our insulated and unheated garage. I suspect that the roof area heated from the sun on the siding as well as some light transmitting through the snow onto the metal roof. I continue to be amazed at the plasticity of ice and snow. With the warmth of the last couple days it all gone. Its been rather hazardous with large chunks of roof bergs breaking off and crashing to the ground.

faronium said...

Kenna is clearly correct.

Assuming this happened in the last week or so this is what we know:

--temperature near, but mostly below freezing
--Dew points below freezing.
--Some sunny days, some partly sunny (based on solar from nearby RAWS).
--Not much precip
--Probably some heat from inside the house and assume more head during the day than night.
--roughly 1foot of snow on the roof

First of all, if the snowpack reached melting throughout, then the whole thing would have broken off before any curled icicle could have formed because wet snow at the freezing point has little strength. This would be mitigated by any ice layers in the snow holding it all together.

There appears to be periods when the snow moves and periods when it doesn't. My guess is that the snow is thin enough to allow enough sunlight to strike the dark colored roof, warm it and melt a thin layer allowing the snow to glide during the day. At night, when the solar heating goes away it all refreezes. This would also promote an ice lens at the bottom of the snow that will help hold the whole works together in case conditions get a bit warm. Because temperatures are roughly freezing or below, once the snow slides past the roof edge, it all refreezes nice and solid/strong. The below-freezing dew point allows evaporative cooling to help prevent undue melt of the snow. It keeps it crusty and strong like the best of us.

The overhanging snow/ice melange will be continuously deforming under the stress of gravity. Ice is a semi-plastic material. Snow is a plastic/granular medium so also capable of deformation in this way. The greatest deformation rates will be right at the roof edge because the mass working on the snow/ice melange will be greatest there (it will be a function of the total length of the overhang, thickness of overhanging layer, and density). By extension, the icicles at the far edge of the overhang will undergo the least amount of stress so will deform the least. Deformation at the roof edge will continue only as long as the angle of the snow/ice overhang is anything but perpendicular to the earth. If the conditions were to cool and the sun hidden behind clouds, eventually the overhanging snow nearest the roof edge would be angled almost vertically or break off.

With each successive day, the snow slides and at night some bend is introduced and the bend is always in the same direction. These creases eventually add up to a curl. If conditions were really consistent from day to day, it would be possible to calculate how many days it took for the curled icicle to form. The most curled icicle is probably behind the post because the radiant heat from the house is blocked allowing greater preservation. The mass of the icicle is small enough that its deformation rates will be much slower than that at the roof edge, so will be continually subject to curling.

This will all continue until the temperature rises enough to weaken the snow at the roof edge when it will all collapse. Or, if conditions stay similar, eventually the weight of the ice will exceed the brittle strength of the snow/ice at the roof edge and it will snap off.

Deek said...

One more comment: Its hard to tell but it looks like the icicle in the first picture is actually touching the post. Perhaps this provided a mechanical force to curve the icicle into a loop

Mark said...

I've seen icicles form at unusual angles when there is a strong wind.

When I was a kid, I attended a 2 story elementary school in Minnesota with slate roofs. In late winter, the sun would melt the bottom layer of the snow/ice and large chunks would slide off like mini-avalanches crashing on the parking lots and side walks below. The falling slabs of ice/snow were dangerous. There was a loud rumble as they came down.

I recorded 1.27 inches of rain at South Vashon from Feb 11, noon through Feb 12, noon. Now there is sunshine with bright blue skies and 53 degrees, very nice. My home town in Minnesota is +9 degrees with blowing snow, not so nice.

CC said...

Curved icicles are very common in the mountains. They are associated with creeping roof dumps, which sometimes take weeks, which occur under certain snow/temperature conditions: There are a number of them in this photo album from my home:

The reverse-curved one which started this thread obviously has something to do with its interaction with the post.

The phenomenon which puzzles me are the snow mushrooms that form around a bit of snow on the edge of the roof crest which doesn't dump because it is over the roof overhang. There is one on the last picture in the album. I don't understand why they form into that circular shape.

tornado.specialist said...

We've seen the curving icicles commonly in the relative flatlands of Oklahoma, thanks to tree limbs that shift positions with the weight or melting of ice thereon. The physical concept fundamentally is the same as in the examples above. Here is one example among many I've seen and photographed:

I have photos of a few even more strongly curved icicles and will post them in time to the same site (SkyPix "Okie Winters" gallery).

Thomas said...

The snow layer curls inward because as it slides off the roof it is compressed on the lower side making that side shorter. (The inner circumference of a ring is shorter than the outer circumference of ring.) The icicle curls inward because as it is tilted inwards by the curl of the snow layer water runs down the outside of the icicle, not uniformly around the icicle). As the water freezes on the outside, or now the lower side, that side of the icicle lengthens, forming an inward curl. If conditions warm up the icicle will go from tilted to vertical again.

Bill said...

Ok, pretty cool icicle puzzle, now solve the puzzle of this stalactite in the beautiful Chapada Diamantina park of Brazil. I couldn't find a still image but this links directly to an image of it on a youtube video:

Thomas said...

Very cool stalactite indeed Bill. Here is my guess. These structures form as calcite, dissolved in ground water, is deposited when the water evaporates from a central tube in the stalactite, exiting, evaporating and leaving the calcite which adds to the length of the stalactite. Nothing new there. But sometimes the water also contains particulate matter, perhaps seasonally during heavy rains. This particulate matter plugs the tube and the acidic nature of the water can bore a second hole to the side of the main tube. Thus the stalactite can change direction. Amazingly it even can go vertical. When its vertical things change. Now the exiting water just collects, forming the bulb, like a bubbling fountain. The bulb allows multiple water exit points, thus the individual exiting calcite spikes. Note the uniformity, equal spacing, of these spikes. Probably from a uniform head pressure in the water. Really fun stuff.

shawn stone said...

I have a picture of a forked icicle ID love to share with you...not sure how though... I've never seen one before!