Freezing Cold

[chrispenycate]

*I'm wondering how rivers and waterfalls behave in a winter with snowfall. Now my lack of knowledge regarding cold climates really got me

Well, I used to ski the black run in Avoriaz where you ski across the near vertical surface of a frozen waterfall. Sort of like skating without the horizontal - edges are critical.

So, autumn (fall) edges of rivers and streams start getting ice film over the surface in the morning when you wake. Swifter current it's ice threads, like horizontal icicles. Mainly, to start with, these melt during the day and reform at night but, little by little as the season advances they stretch further, and last longer, until you have a solid ice sheet all along the banks, extending ever further towards the centre. This is thin and brittle, and animals and birds break it up to drink. The faster flowing the watercourse the more irregular and bumpy the ice sheet, and rapid flows will freeze up later than

A waterfall freezes in icicles along the edge, which thicken as more moisture freezes on by layers. I've never seen a smooth frozen waterfall, though I've no doubt they exist; all the ones I've met have been lumpy. If they come from high springs, or glacier melt which stops during the winter, they often freeze clean through into solid sheets. Snow doesn't tend to stick to them, which means that as you cross, on skis, sledge or snowshoes friction suddenly changes from something like wedding cake icing to one of those bathroom windows you can't actually see through. Fun.

On your more sedate river or lake the ice sheets meet in the middle, and freezing slows, as wind can't tear molecules from the surface cooling it anymore. Heat has to conduct up through the ever thickening ice layer, and there are almost always bubbles of air trapped which further slow the process, and frequently layers of snow (very good thermal insulation).

In calm air, the ice sets smooth enough to do figure skating, but if it freezes with a cold wind the surface gets ripples, and broken ice plates sticking out of it. Incidentally, when it gets really cold the ice isn't slippery any more, as your weight can no longer generate enough pressure to melt it to lubricating water, but that's silly cold temperatures - minus thirty, forty degrees (Centigrade or Fahrenheit, doesn't really matter. Chilly.)

Well, I can lecture for hours, but it's probably better to let someone else from a cold region give answers from another perspective, unless there are some specific questions?

 

[Nihal]

Thanks! That's really valuable information, I wouldn't be able to imagine all those details the first-hand experience provides.

I did a little more research on my own because I have a very specific situation in my story. It's a citadel, located in an artificial island in the middle of a fall of epic proportions—think more in Victoria or Iguazu, not Niagara. Until yesterday I didn't realize it could see light snowfall, and sometimes freezing temperatures during the worst winters.

I'm less than clueless when it comes to cold climates (but if you ever need to know about tropical climates, hot summers and thunderstorms you may ask me).

Based on what happens in Niagara I came to the conclusion that the complete freezing of this fall would be extremely unlikely, but if the river freezes upstream the falls could be reduced to a trickle.

It would be helpful to know more about the melting process of a river/waterfall and the threats involved. Other general considerations about ice, snow and cold are also helpful. I'll have a couple of dumb characters crossing the plateau above these falls during the winter.

 

[Terry Greer]

Thaws are interesting too.
In rivers large ice blocks can do huge amounts of damage as they drift downstream, and lakes empty beneath the ice causing the surface to fragment and buckle leaving huge caves beneath along the waterline.
I'd also suggest you l;ook at this from the Human Planet series (which is astounding and along similar lines):
Race against the tide, risking death under huge blocks of ice - Human Planet: Arctic - BBC One - YouTube

I'd also check out references to the old medieval frost fairs on the Thames.

 

[ThinkerX]

Lifelong dweller in the about to be frozen north country here (frost on the ground past week or so in the mornings).

Yes, waterfalls do freeze solid...at least the smaller ones do. Icicles are...a weak variant of frozen waterfalls.

Lakes tend to get a thick crust of ice 'up top'. Before it snows, they look like giant sheets of glass...and like glass, that ice can and does crack, with groaning sounds mistakable for thunder...or a gunshot. Unless the ice is very new (cracking underfoot with each step) this is not a prelude to falling through the ice. It does mean something else in the winter, once the snow covers the ice: overflow.

With overflow, tiny amounts of water seep *up* through the cracks in the ice, turning the snow above it into faintly discolored mush. This discoloration is easy to miss, and can be concealed completely with a fresh snowfall. What this means for travelers is you are walking or skiing or snow-machining along a nice firm packed trail...and then you sink. You don't go through the ice, but snow machiner's can get stuck but good. You also get wet - and wet clothes plus below freezing weather is not good.

Overflow is a hazard of winter travel along rivers. Plus, the river is still flowing beneath the ice (at least with the deeper rivers), which translates to weak spots in the ice. I get to listen to reports each winter of people falling through these weak spots and drowning...and many of them are experienced north country types.

In spring the ice 'rots,' melting into sheets that resemble thousands upon thousands of upright glass soda bottles melted together. On the lakes, towards the end of this process, these sheets clash against each other with each slight current, making lovely silver-bell like sounds. The thawing process is much less even for the rivers. The ice will vanish from the parts with the strongest currents, but sheets of ice will cling to the banks, sandbars, and islets, breaking loose weeks later.

True 'ice damns' or winter breakups are rare. We had one here a few years ago that worked its way down stream at something like 1 kilometer per hour. It literally scoured the banks as it passed, smashing boats, trees, and riverside buildings.

At work, I get to drive down a road that floods each winter...even though the water is froze solid. The road builders rut the road into a hillside spring. Summer, the water flows to a culvert and drains away. Winter, the water bubbles to the surface, and turns to ice. First it fills the ditch, then it creeps onto the road. Driving that stretch can be a real pain.

 

[AliceS]

I lived in Aspen, Colorado for a couple years. Walking in the freezing cold is painful. There, it's a dry cold and you can become dehydrated easily. You want to make sure that all entrances to your clothing are sealed - sleeves cinched tight, neck buttoned up. Your nose hairs can freeze if it's cold enough and breathing gets hard. Inhaling cold air can make you cough. And if you have sensitive teeth, it's like iced drinks, if you breath through your mouth. Your face gets numb. Exposed skin burns when you come in out of the cold. Mittens are better than gloves because they make more of a pocket to hold warmth. My fingers and toes always got cold. They'd be bone white and ice cold by the time I walked home from the bus stop. Then they'd get red and burn until they warmed up. Cold water could feel like it was hot because my skin was so cold. I shivered constantly, which can give you muscle aches after awhile.

I worked for the ski company there for one season. They loaned me fabulous goretex clothes to work outside in. Totally wind proof. I was warm as toast while checking ski passes on the lift. Nothing in comparison to the cheaper items I could afford on my own, so I always had lots of layers. And hats are essential. Especially covering the ears. They are very thin and freeze easily.

I also worked for a glass company. Not sure if this is something you could use, but when the temp dropped too low, glass got very fragile. I found out that the heat of your hand on a car window (left out in the cold over night) could shatter it.

And you know about fur - in those temps you wear your fur coat with the fur on the inside.

 

[SeverinR]

January I took over 100 pictures of frozen waterfalls.
deviantART: 403 Forbidden
deviantART: 403 Forbidden

Only two I found online. There is one that is probably 20-30 foot around and over 100 ft drop.
I will see if I can find it on my home computer.


It was a great day, 50degrees(f) jacket weather, took my little dog and she never shivered.

 

[Svrtnsse]

That's some really cool pictures.

 

[SeverinR]

http://media-cache-ec0.pinimg.com/736x/62/0a/75/620a75008e4aa8e6d0d86e96f33cd0a3.jpg
Here is one in the making. This one is not mine, just found on web.