Ice and waves

Waves going through very fresh, still flexible ice. What an exciting topic :-) We had a first look at the picture below in the last blog post already, when we looked at stages of ice formation. Can you see how the pancakes are deformed by waves going through?

It’s a little more difficult to see in the picture below, where a storm drain drips into the fjord. Can you make out how the wave rings are spreading through the thin ice?

And one thing that I found super fascinating was that ducky ice-breaking: You see the open water bit just behind it, and there are a lot of waves. But then you also see those waves spreading into the ice! Poor ducky must have put a lot of energy into this…

My favourite picture, though is the one below: A crisscross of waves and an ice floe that moves (obviously) with both wave fields!

This even works if there is more ice than just one lonely flow:

How awesome is that??? :-)

Ice forming on Kiel fjord

One thing I really like is watching ice form. Well, maybe not watching the actual freezing (don’t have the attention span for that) but looking at all the different stages.

At first, you have all the small, individual needles that still slush around.

Then, the needles start sticking together, and if there is a little wave action, the ice breaks apart into individual pancakes, which bump into each other and start piling up along the edges.

If the wave action isn’t too bad, those pancakes can freeze together, forming a closed ice cover.

Sometimes you can also see several stages at once, like in the picture below: Open water out on the fjord, slush a little further in, then smaller pancakes and then larger pancakes. Not very surprising: Most wave action in the middle of the fjord, and the further you get towards the shore, the more waves have been dampened by the ice, so the larger the ice floes can grow.

Here you can actually see waves going through the ice-covered area, giving you an idea of how flexible the pancakes still are. More on that in the next post… ;-)

Here you see all the stages in one pic again. Together with the raising sun it makes for very pretty pictures! :-)

Desublimation: When water vapour freezes to ice without becoming liquid in between

One of my favourite phenomena right now is desublimition, or deposition: The phase transition of water vapour to ice that doesn’t go through the liquid phase. It happens when moist air is cooled below the dew point and condensation doesn’t occur spontaneously: When the supercooled water vapour then gets in touch with a cold surface, it turns to ice immediately. And the results are incredibly beautiful!

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These pictures are all from a trip I took with my godson and his family to Möhne Reservoir, the largest artificial lake in western Germany. You can see we were actually on a shore: What a surreal mixture of shells, leaves and frost flowers.

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And we initially just wanted to go over and have a look at the fog that we saw across the Reservoir from where we were throwing stones in the water

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Getting closer, we were almost afraid that we’d encounter dementors there. We could feel it getting a lot colder, and there was frost on the shore and ice on the water… Spooky :-)

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Frost flowers on ice cream: When you start thinking about phenomena and something really annoying, all of a sudden, becomes really cool.

Frost flowers on ice cream. You must have seen them before: They sometimes occur when you’ve had some ice cream, put the left-overs back in the freezer, and take them out again. And there you have it: Water-ice crystals all over your lovely ice cream! Completely annoying because, obviously, they only taste like water and mess up your whole ice cream experience (or is that only me)?

You know I’m kinda fascinated with ice crystals on frozen blended strawberries, but last time I had some, there weren’t only crystalline structures, but there was frost on it:

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Frost occurs when water vapour freezes without going through the liquid phase. Look at the awesome crystals!

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Once I started thinking about the process that formed the ice and realised that those were actually frost and not just ordinary ice crystals, they all of a sudden stopped being annoying and instead became something that I kinda look forward to finding when I open a tub of my frozen blended strawberries. Because the structures are different every time, and really really pretty! And also how awesome is it to know that those ice crystals formed from water that wasn’t even liquid? Yes, this is the kind of stuff that makes me happy! :-)

Using the “melting ice cube” experiment to let future instructors experience inquiry-based learning.

Ice cubes melting in fresh water and salt water. By Mirjam S. Glessmer

Using the “melting ice cube” experiment to let future instructors experience inquiry-based learning.

I recently (well, last year, but you know…) got the chance to fill in for a colleague and teach part of a workshop that prepares teaching staff for using inquiry-based learning in their own teaching. My part was to bring in an experiment and have the future instructors experience inquiry-based learning first hand.

So obviously I brought the ice cubes melting in fresh water and salt water experiment! (Check out that post to read my write-up of many different ways this experiment can be used, and what people can learn doing it). On that occasion the most interesting thing for me was that when we talked about why one could use this — or a similar — experiment in teaching, people mainly focussed on the group aspect of doing this experiment: How people had to work together in a team, agree to use the same language and notation (writing “density of water at temperature zero degree Celsius” in some short syntax is not easy when you are not an oceanographer!).

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And this experiment never fails to deliver:

  • you can be 100% sure that at least in one group, someone will say “oh wait, which was the salt water again?” which hands you on a plate the opportunity to say “see — this is a great experiment to use when talking about why we need to write good documentation already while we are doing the experiment!”
  • you can also be 100% sure that in that group, someone will taste the water to make sure they know which cup contains the salt water. Which lets you say your “see — perfect experiment to talk about lab safety stuff! Never ever put things in your mouth in a lab!”
  • you can also be sure, that people come up with new experiments they want to try. At EMSEA14, people asked what would happen if the ice cubes were at the bottom of the beaker. Today, people asked what the dye would do if there was no ice in the cups, just salt water and fresh water. Perfect opportunity to say “try! Then you’ll know! And btw — isn’t this experiment perfect to inspire the spirit of research (or however you would say that in English – “Forschergeist” is what I mean!). This is what you see in the pictures in this blog post.

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So yeah. Still one of my favorite experiments, and I LOVE watching people discover the fascination of a little water, ice, salt and food dye :-)

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Photo taken by Ulrike Bulmann
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Photo taken by Ulrike Bulmann

Btw, when I gave a workshop on active learning last week and mentioned this experiment, people got really really hooked, too, so I’ll leave you with a drawing that I liked:

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Frost flowers – when water vapour freezes to ice without going through the liquid phase. Examples “at sea”

Frost flowers on the ice of the Schlei in Schleswig. By Mirjam S. Glessmer

Frost flowers! I learned about those in the context of Arctic and Antarctic ice formation. I kinda assumed that ice flowers only formed in salt water, because I remember hearing about how the ice needles that form wick up brine and that, due to their large surface (which you will remember noticing in the last post where we looked at them forming on trees), they are super important in the air-sea exchange of all kinds of stuff,  like for example bromine. So imagine my excitement when I saw them growing the other day!

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Frozen Schlei river in Schleswig

Frost flowers are really pretty by themselves, but they also tell us a lot about recent weather conditions. For example, they only form when the air is A LOT colder than the water/ice surface. Do you know the snowy ice crystals you sometimes find on the inside of ice cream containers when you’ve opened and refrozen them? Yep – same thing! I even suspect that the ice crystals I was talking about in this post are also frost flowers.

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Frost flowers

I find it really fascinating how they are distributed over the larger surface of the Schlei river.

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Schlei river in Schleswig coated in frost flowers

Here, for example, you see them forming on the edges of ice that has been broken up by some mechanical process. Judging from their placement, I would suspect that they only formed after the ice was broken and some of the pieces tilted up.

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Cracked ice and frost flowers

Here, they were probably everywhere, but then the ice got broken up and some parts submerged. When the water there refroze, no snow flowers formed, just “normal” ice. However, the existing snow flowers seem to have continued growing!

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Ice with frost flowers. Partially submerged and then refrozen into “normal” ice

The really interesting thing is that frost flowers don’t actually form from the water that is freezing below, but from water vapour in the air. Which, btw, explains why they can form on benches, ice cream lids or trees (all of which would be really difficult if they could only form on open water surfaces).

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Ice with frost flowers. Partially submerged and then refrozen into “normal” ice

Above you see a larger part of the Schlei’s surface: Seems like there used to be frost flowers everywhere, but when the ice broke up, some of it got pushed out of the water, and as such preserving the frost flowers and letting them continue to grow. Meanwhile, other parts got flooded and only normal ice formed there. Maybe because the temperature gradient at that point wasn’t large enough any more?

Isn’t this just beautiful??? I could watch this all day, every day.

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Frozen Schlei river in Schleswig with frost flowers

But let’s look at some more details. No idea why that patch of frost flowers formed there! But they seem to always start in small patches, which eventually grow together if the conditions are stable enough over long enough periods of time.

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Frost flowers on ice

Here, we see the opposite situation to the one a couple of pictures up: “Normal” ice had formed, and then was broken up. And then, when the crack froze over, frost flowers formed!

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Frost flowers growing in a crack in the ice

Very cool stuff!

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Frost flowers

Yep, I would still just sit there and watch!

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Frozen Schlei river in Schleswig

Frost flowers – when water vapour freezes to ice without going through the liquid phase. Examples on land

Frost flowers on the ice of the Schlei in Schleswig. By Mirjam S. Glessmer

What happens when water vapour freezes to ice without going through the liquid phase? Frost flowers!!!

That’s when trees suddenly look like this:

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Frosted tree.

Btw – the stem of that tree is painted white! That’s just to confuse you a little but…

But let’s take a closer look. This is what the branches look like: Tiny ice needles growing on the individual pine needles! And the orientation of the image below is correct. They are growing to the side!

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Frosted tree.

You can clearly see them all growing to one direction, to one side!

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Frosted tree.

When you take off a bit of frost, this is what it looks like. Needles, but with a fractal 3D structure! Since what happened here (water vapour freezing without becoming liquid in between) is basically snow forming on the surfaces down here instead of in the clouds up above, it isn’t too surprising that snow is exactly what the frost bits feel like.

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A piece of frosting. This picture isn’t blurry – the ice needles have a fractal 3D structure!

Look below, you can clearly see the frost only growing to one side (and this picture is the right way up, too!):

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Frosting on tree branches

Doesn’t it make you want to sit there and just watch?

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What a nice picknick spot!

Although every time the slightest of breezes comes, this is what happens:

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Tree being de-frosted by wind

Also really cool: These plants growing on a balcony behind a glass railing. Only the tips have been frosted!

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Plants on balcony with frosted tips

And if you were wondering what this post has to do with oceanography, check out the image below. Can you spot it?

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Frozen Schlei river in Schleswig

Can you spot it now? No, not my niece (although she is pretty cool, too!), the frost flowers!

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Schlei river in Schleswig with frost flowers

We’ll talk about those next time :-)

Reading ice on a river as tracer for flow fields

Ice on Elbe river in Hamburg. By Mirjam S. Glessmer

For most of my readers it might be pretty obvious what the movement of floating ice says about the flow field “below”, but most “normal” people would probably not even notice that there is something to see. So I want to present a couple of pictures and observations today to help you talk to the people around you and maybe get them interested in observing the world around them more closely (or at least the water-covered parts of the world around them ;-)).

For example, we see exactly where the pillars of the bridge I was standing on are located in the river, just by looking at the ice:

What exactly is happening at those pillars can be seen even more clearly when looking at a different one below. You see the ice piling up on the upstream side of the pillar, and the wake in the lee. Some smaller ice floes get caught in the return flow just behind the pillar. Now imagine the same thing for a larger pillar – that’s exactly what we saw above!

And then we can also see that we are dealing with a tidal river. Looking at the direction of the current only helps half of the time only, and only if we know something about the geography to know which way the river is supposed to be going.

But look at the picture below: There we see sheets of ice propped up the rails where the rails meet the ice, and more sheets of ice all over the shore line. As the water level drops due to tides, newly formed ice falls dry and that’s all the sheets of ice you see on land.

The bigger ice floes in the picture have likely come in from the main arm of the Elbe river.

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Small port on a tiny bay on the Elbe river in Hamburg. Look at the sheets of ice on shore!

It is actually pretty cool to watch the recirculation that goes on in all those small bays (movie below picture). Wouldn’t you assume that they are pretty sheltered from the general flow?

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Can you make “boring” math or physics exciting by relating it to the adventures of a research cruise in Antarctic? Elin can!

My friend Elin is currently on a research cruise in Antarctica and you really need to check out her blog. She is writing about life at sea, including the most beautiful photos of sea ice. Today’s post is called “ice or no ice” and describes the first couple of days of the research cruise. Elin combines the catching narrative with exercises and experiments that will be conducted by at least 30 schools all over Norway! And maybe you can use some of her posts, exercises and experiments in your teaching, too?

Today, for example, the exercises are all about ice. Depending on how much brain power you want to invest and how much prior knowledge your students have, you could for example do an exercise about Archimedes’ principle, calculating how much of an ice floe is visible above the water’s surface, and how many scientists you could put on it before people start getting wet feet. Or, more challenging, you could work with real data that Elin provides to practice your statistics and look at the annual cycle of sea ice in Antarctica. Or you could even set up differential equations for how ice thickness increases over time.

There will be new exercises every Monday for the next two months. How exciting!

Elin’s blog, “På tokt i Antarktis“, is available in English, Norwegian and Swedish. So you can use it not only to practice your maths and physics, but also your language skills! :-)

Btw, if you got hooked and can’t nearly get enough of reading about that research cruise, there is a second blog that tells you, for example, about the different kind of New Year’s Eve the scientists and crew had before heading off to Antarctica. Also very much worth a read!

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Temperature-driven overturning experiment – the easy way

In my last post, I showed you the legendary overturning experiment. And guess what occurred to me? That there is an even easier way to show the same thing. No gel pads! (BUT! And that is a BIG BUT! Melting of ice cubes in lukewarm water is NOT the process that drives the “real” overturning! For a slightly longer version of this post check this out).

So. Tank full of luke warm water. Red dye on one end. Spoiler alert: This is going to be the “warm” end.

overturning-ice-1Now. Ice cubes on the “cold” end. For convenience, they have been dyed blue so that the cold melt water is easily identifiable as cold.

overturning-ice-2A very easy way to get a nice stratification! And as you see in the video below, awesome internal waves on the interface, too.

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And because I know you like a “behind the scenes”:

I took this picture sitting on my sofa. The experiment is set up on the tea table. The white background is a “Janosch” calendar from 15 years ago, clipped to the back of a chair. And that is how it is done! :-)

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