Today we are doing the melting ice cubes experiment in fancy glasses, because Elin is giving a fancy lecture tonight: The Nansen Memorial Lecture of the Norwegian Science Academy in Oslo! Cheers!
We each had green ice cubes in our glasses, but one of our glasses contained fresh water and the other one salt water, both at room temperature. Can you figure out who got which glass?
This time lapse might give you a clue…
To read more about this experiment, check out this blog post!
What I find really fascinating about the planetary Rossby wave experiment is to look from the side and see the columns develop and move around the tank.
Here is a side-view camera plus the top view, both cameras rotating with the tank. The movie is sped up 20x so in about 22 seconds, you will have a good idea of what happens:
And here is the same movie in real time. Here you can really beautifully watch the plumes of dense water sinking to the bottom while the whole column is rotating.
https://vimeo.com/364353173
One thing to avoid when running this experiment: Don’t put the ice cube too close to the side of the tank, otherwise it will get stuck there. I don’t know if it was surface tension keeping it so close to the wall or if, since it couldn’t rotate, it decided not to move at all, but in any case: If the ice cube is too close to the wall, it will get stuck. In our case, the dense water then sank down in the small gap between the sloped bottom and the wall of the tank (as you see in the picture below, which is looking under the sloping bottom towards the deep end of the tank).
You still see columns forming underneath the sloping bottom, but that wasn’t quite what we were aiming to do…
On the GEOF105 student cruise that I was lucky enough to join like I did last year, I happened to observe what you see in the picture above: Standing waves in a bucket! And this isn’t a staged photo, this is me taking a picture of a student at work.
We are looking at the bucket the students use to take surface water samples which they measure on deck. The bucket happens to stand just above the engine room. Which leads to vibrations. Which, in turn, leads to waves. Many different kinds of waves! In addition to what you see above, we find, for example, plain circular waves. They might look like they do in the picture below:
And here is a short movie of the waves, first in real time, then in slow motion.
Sometimes the circular waves also have other wave lengths.
The next pattern that develops from a monopole (like the one you see above) is my favourite: A monopole with higher order stuff developing at the edge of the bucket.
Watch the movie below to see it in motion (first at real speed, then in slow motion).
The next step, then, is water that almost looks as if it was boiling. Like so:
Here is a movie of the bucket with the “boiling” wave pattern, again in real time first and then in slow motion.
The movie below shows a close-up of some of the waves in the “boiling” state, when there was enough energy in the system to throw drops up in the air. The movie goes from real time to slow motion. Careful when you play it, I left the sound in in order to show how the frequency of the waves is the same as the frequency of the engine. (And because of the annoying sound, it doesn’t start up automatically, so you have to click to play)
Here is a movie that shows the bucket in different positions, shot continuously to show how quickly the wave pattern develop and also how close together the different spots with the different pattern are located. Thanks for playing along, Kjersti!
So clearly the location has an influence on what wave pattern develops. But what are other important factors? We tested material, shape and size of the container.
A small plastic bucket which is almost cylindrical, for example. Guess what happens?
We can get the same wave pattern as in the large bucket! The movie below shows three different wave pattern. When the frequency suddenly changes that’s because the movie is in parts played in slow motion.
As to material: It seems to be important that it’s flexible. Iron cast pans don’t work (yes, there is water in it!), neither do metal lunch boxes…
And round shapes make nicer waves. But the rectangular vanes of the surface drifters (aka paint roller trays) also make pretty pattern! But now the waves are, unsurprisingly, only parallel to the edges of the tray.
Yep, this is the kind of stuff that makes me really happy! :-)
And now we have arrived in the part of Norway that, to me, feels like home rather than “oh wow, impressive landscape”. Even though the landscape is still impressive! But also very familiar now.
And very beautiful!
Especially with these low clouds randomly hanging out above the fjords.
And are you going to be disappointed if I tell you that I will be taking the night train on my way back home?
I love the little meandering river in the picture above!
We are now approaching the west coast of Norway and all prejudices when it comes to weather over there are being confirmed. It’s grey and overcast. Still, there is a lot of cool water watching to be done on this train ride!
I think it was around this point of my 7 hour train ride, from which I sent a minutt for minutt live broadcast to my friend Kristin, that she pointed out that she had just noticed the common thread in the pictures I was sending: Water!
What a surprise… ;-)
Anyway, it’s getting darker outside, so the quality of the pictures is rapidly decreasing, but I will still show you some rapids in the rivers.
Because they just look super awesome!
And again, waves breaking upstream because the river is flowing so fast, it’s ripping their bases away from underneath them.
And some impressive gorges!
…and very low-hanging clouds.
But the landscape is a lot lusher and greener again!
And I love water falls.
And rapids.
And more water falls!
And now we’ve reached the heights where there is fresh snow! And also where there are wild rivers. Don’t know which I find more exciting :-)
Ok, yeah, it’s definitely the rivers that I find more exciting. Also, isn’t it funny that at first glance, the river seems to be flowing left-to-right, because that’s the direction in which the waves break? It’s flowing right-to-left, though, and the waves are breaking in an upstream direction because the water is just flowing so fast, it’s ripping the carpet out from underneath their feet, so to speak.
And now we have arrived in winter wonder land :-)
…where there is some new ice on the more sheltered parts of the lakes, too!
And now we on our way back down on the west side of the mountains. Snow only on the higher peaks, not at ground level any more.
And now it’s properly overcast and occasionally also snowing!
But let’s end this part of the journey with this beautiful outflow of the lake, and the standing waves that look as if they were braided into each other. So pretty!
While I was on the train from Oslo to Bergen for almost 7 hours, I sent a lot of pictures to my friend Kristin who had expressed an interest in virtually joining the trip.
And it is a very pretty trip indeed!
Also really interesting wave watching, do you notice the white caps on the lake below? Must be quite windy here, too!
And an accidental tractor in the wave watching pic, but it looks actually quite interesting for a change!
I find it also pretty fascinating how everything looks more autumn-y as we go higher up the mountains.
And, of course, I love watching the rivers up here with all their rapids!
We are slowly approaching the tree line. See how vegetation is already very different from where we started out?
But it’s still quite windy, so lots of waves to be seen! Some even with white caps.
And here we see waves traveling around this little headland. Isn’t it fascinating to see how the wave direction is different on either side of the headland?
And some more waves changing direction after they have propagated out of the wind and around another little headland.
And some places are sheltered from the wind so that you see individual gusts of wind quite clearly!
Also — beautiful weather for the train ride! That is, at least, until…
…we are getting closer to the highest point. It’s starting to get overcast…
Oh, and there is the first snow on the mountain peaks in the back!
And here we are — at my favourite museum, the Fram museum!
And I think I have in previous posts said all I can possibly say about the waves you see in this picture. But they are very beautiful nevertheless :-)
As soon as the ferry had arrived in Oslo, I ran off and across the city, because we are up for the next part of the adventure: A train trip across the mountains! Stay tuned…
Next attempt at the topographic Rossby wave! This time with following the geosci.uchicago.edu instructions more closely…
…and then the tank had hickups, so we did get waves, but a lot more diffusive than we had hoped, because the tank slowed down a lot more and in a more bumpy fashion than I had planned…
For a demonstration of topographic Rossby waves, we want the Coriolis parameter f to stay constant but have the depth H change. We use the instructions by geosci.uchicago.edu as inspiration for our experiment and
I ran my new favourite experiment again, the planetary Rossby waves. They work super well on the DIYnamics table we built in Kiel and they also worked really well the other day in Bergen.
I mainly ran it today because I wanted to get an idea of how robust the experiment is, i.e. what to prepare for when running it with students in terms of weird results that might have to be explained.
Here is a side view of the square tank with a sloping bottom. The blue ice cube is melting. The melt water is forming a Taylor column down to the bottom of the tank. Some of it then continues down the slope.
Here we are looking at the slope and see the same thing (plus the reflection at the surface). Note how the ice cube and its meltwater column have already moved quite a bit from the corner where I released it!
When the blue ice cube had crossed half the width of the tank and the blue melt water had almost reached the other edge, I released a green ice cube. Sadly the dye wasn’t as intense as the blue one. But it’s quite nice that the wave length between the individual plumes going down the slope stays the same, for all the blue plumes as well as for the new green ones.
Here in the side view we see the columns of the blue and green ice cube, and we also see that each of the plumes going down the slope still has Taylor columns attached at its head.
Here is an accelerated movie of the experiment, 20x faster than real time. Not sure why there is still sloshing in the tank (this time I made sure it was level), but it’s very nice to see that the ice cubes are spinning cyclonically, faster than the tank! As they should, since they are sitting on Taylor columns…
I think next time I really want to make a side view movie of the Taylor columns and plumes. Not quite sure yet how I will manage the lights so they don’t get super annoying…