One day in the office at the Geophysical Institute in Bergen last Friday, and for the first time in a long time I am writing a little bit of oceanography and tank experiments again: My colleague Stefanie Semper and I published a SERC “Teach the Earth” activity on “ocean currents and overflows”! This activity is […]
For all of you who know and love my “24 days of #KitchenOceanography” series (and for those who need to quickly look up what that was about and then fall in love with it ;-)) — you can now buy it as a book! The book contains 24 easy experiments, embedded in the bigger context […]
I did this demo for my freediving club Active Divers (and if you aren’t following us on Insta yet, that’s what I am taking all these pretty pictures for!): 1.5l PET bottle with holes punched in every 2cm, then filled with water. Looks cool and works pretty well (except the second hole from the bottom up, […]
Since our Denmark Strait tank experiment from 2013 (see here in a post from 2014!) is still the one I refer to when I want to point to pictures of such an overflow experiment, I decided to do the experiment again to take new (and hopefully better) pictures. Three experiments later, I am not sure […]
For the Christmas party of my freediving club, Active Divers, I made a freediving-themed #KitchenOceanography “escape game” (of sorts). If you are interested to use it for your own purposes, please feel free to contact me for detailed instructions and material lists etc! This is how it went: We formed teams with three players in […]
At the end of last year, I did a poll on Twitter, asking what people would like to see more of in 2021: Kitchen oceanography, wave watching, teaching & scicomm tips, and other things. And 2/3rds of the respondents said they wanted more kitchen oceanography! So obviously my strategy was to do a photo shooting […]
When students have only one day at sea, it’s important to prepare them well for what will happen there so they get the chance to make the most of the experience. For example, let’s consider a one day student cruises just outside of Bergen. Students are divided in teams that use different types of instrumentation and […]
I gave a talk withing iEarth’s seminar series to introduce myself to the network last week. And since it was the last lecture before the Christmas break, I tried to turn it into a fun event including kitchen oceanography and wave watching! Watch the recording at https://iearth.no/en/2020/12/17/iearth-digital-learning-forum-mirjam-glessmer/ or below:
We’ve become quite experienced with remotely-controlled rotating tank experiments, but the current lockdown brought us into yet another new-to-us situation: We had plans to film and live-stream tank experiments from Geomar, but not being employed there, I am currently not allowed in the building! So what happened this morning is that Torge and I met […]
Torge and I are planning to run the “tilting of a frontal surface under rotation / cylinder collapse” experiment as “remote kitchen oceanography” in his class on Thursday, so I’ve been practicing it today. It didn’t work out quite as well as it did when Pierre and I were running it in Bergen years ago, […]
Last Thursday, Torge & I invited his “atmosphere & ocean dynamics class” to a virtual excursion into my kitchen — to do some cool experiments. As you know, I have the DIYnamics rotating table setup at home, so this is what it looked like: We did two experiments, the very boring (but very important) solid […]
A very common misconception when looking at atmosphere & ocean dynamics in a rotating tank is that the center of the tank represents one of the poles and the edge of the tank the equator. And there is one experiment that — I fear — might reinforce that misconception, and that is the one we […]
This is the long version of the two full “low latitude, laminar, tropical Hadley circulation” and “baroclinic instability, eddying, extra-tropical circulation” experiments. A much shorter version (that also includes the end cases “no rotation” and “no thermal forcing”) can be found here. Several of my friends were planning on teaching with DIYnamics rotating tables right now. […]
The first experiment we ever ran with our DIYnamics rotating tank was using a cold beer bottle in the center of a rotating tank full or lukewarm water. This experiment is really interesting because, depending on the rotation of the tank, it will display different regimes. For small rotations we get a low latitude, laminar, tropical […]
Several of my friends were planning on teaching with DIYnamics rotating tables right now. Unfortunately, that’s currently impossible. Fortunately, though, I have one at home and enjoy playing with it enough that I’m Playing with it Making videos of me playing with it Putting the videos on the internet Going to do video calls with my […]
Several of my friends were planning on teaching with DIYnamics rotating tables right now. Unfortunately, that’s currently impossible. Fortunately, though, I have one at home and enjoy playing with it enough that I’m Playing with it Making videos of me playing with it Putting the videos on the internet Going to do video calls with my […]
It’s #KitchenOceanography season! For example in Prof. Tessa M Hill‘s class at UC Davis. Last week, her student Robert Dellinger posted a video of an overturning circulation on Twitter that got me super excited (not only because as of now, April 15th, it has 70 retweets and 309 likes. That’s orders of magnitude more successful than any […]
Reposting a guest post I wrote for the @DIYnamicsTeam‘s blog: When we came across the DIYnamics article right after its publication, Torge and I (Mirjam) were very excited about the endless possibilities we saw opening up with an affordable tool like the DIYnamics rotating table. We applied for, and were granted, money for an “innovative […]
(Not true, there were 22 tweets, but apparently I can’t count! :-D) For those of you that don’t follow my Twitter, here is what I posted over there the day our Nature paper got published: Published online in @Nature today: “Ice front blocking of ocean heat transport to an Antarctic ice shelf” by @a_wahlin @nadsteiger […]
A long, long time ago (ok, in fall of 2017) I got the chance to join Elin Darelius and Anna Wåhlin’s team for a measuring campaign at the Coriolis platform in Grenoble for several weeks. I was there officially in an outreach officer-like role: To write and tweet about the experiments, conduct “ask me anything” […]
Inspired by a recent twitter comment on how our tanks are higher-walled than those usually used on the DIYnamics rotating tables, today I’ll talk about why we went for those. Full disclosure: Mainly for practical reasons (see below). BUT: having high-walled tanks is really helpful for many experiments because they make it a lot easier […]
Yesterday, we’ve had four rotating tables operating simultaneously, for three different experiments. The one that everybody is gathering around in the picture above is our favourite experiment: a slowly rotating tank with cooling in the middle that shows a nice 2D circulation instead of an overturning as we would expect in a non-rotating system. A […]
I had so much fun playing with rotating tank experiments on a cone this afternoon! And with Torge Martin (who I have the awesome #DryTheory2JuicyReality project with) and Rolf Käse (who got me into tank experiments with an amazing lab course back in 2004, that I still fondly remember). We tried so many different things, […]
Remember the experiment on Nansen’s observation of “dead water” that Elin & myself set up as part of GEOF213? Our movies of this experiment are now featured in a brilliant Youtube video by my friend, the german science communicator Doktor Wissenschaft! Check it out! (English subtitles available) I feel so proud to have contributed to […]
On Thursday, I wrote about the thermally driven overturning circulation experiment that Torge and I did as past of our “dry theory 2 juicy reality” experiments, and mentioned that it was a non-rotating experiment in a class about rotating fluid dynamics. I showed you the rectangular tank, but we also used a cylindrical tank with […]
You might have noticed them in yesterday’s thermally driven overturning video: salt fingers! In the image below you see them developing in the far left: Little red dye plumes moving down into the clear water. But wait, where is the salt? In this case, the “double” in double diffusion comes from heat and dye which […]
Today was the second day of tank experiments in Torge’s and my “dry theory 2 juicy reality” teaching innovation project. While that project is mainly about bringing rotating tanks into the theoretical teaching of ocean and atmosphere dynamics, today we started with the non-rotating case of a thermally driven overturning circulation. Very easy setup: A […]
I’m actually at a loss for words. Amazing? Spectacular? So much fun? All of that! Today was the first time Torge and I tried our four DIYnamics-inspired rotating tables in teaching. (Remember? We want to use 4 rotating tables simultaneously so students can work in small groups rather than watching us present experiments, and also […]
When Tor came to visit me in GFI’s basement lab a couple of days ago, he told me about an experiment he had seen in Gothenburg in the seventies. So Elin and I obviously had to recreate it on the spot. Therefore today, we are comparing phase- and group velocities in deep and shallow water! […]
This experiment just doesn’t want to be filmed by me. Even though I spent more time on preparation of this experiment than on almost any other experiment I have ever done! I have written up the theory behind this experiment, run it with a blob of dye to visualize the wave, then with a ring of dye. […]
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 […]
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… Setup of […]
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 […]
And here is my new favourite experiment again: Planetary Rossby waves! This time filmed with a co-rotating camera. We have a square tank with a sloping bottom at solid body rotation (except this annoying slogging because the rotating table wasn’t levelled out [meaning: I didn’t level it before starting the experiment…]). We then release a […]
Finally trying the topographic Rossby wave experiment I wrote about theoretically here! And it is working — ok-ish. If you know what you are looking for, you can kind of see it. So check out the picture above so you know what you expect to see below ;-) We are rotating the tank fairly rapidly […]
This is seriously one of the easiest tank experiments I have ever run! And I have been completely overthinking it for the last couple of weeks. Quick reminder: This is what we think hope will happen: On a slope, melt water from a dyed ice cube will sink, creating a Taylor column that will be driven […]
For both of my tank experiment projects, in Bergen and in Kiel, we want to develop a Taylor column demonstration. So here are my notes on the setup we are considering, but before actually having tried it. Since water under rotation becomes rigid, funny things can happen. For example if a current in a rotating […]
For both of my tank experiment projects, in Bergen and in Kiel, we want to develop a Rossby wave demonstration. So here are my notes on three setups we are considering, but before actually having tried any of the experiments. Background on Rossby waves I recently showed that rotating fluids behave fundamentally differently from non-rotating […]
In earlier posts on drop photography, you might have noticed that the reservoirs for the water that drops out and creates the beautiful liquid art has a weird cork on top, sealing it off, and a glass pipe sticking through. I’ve been wanting to explain what that’s all about for a while, but had to […]
When you stop a rotating tank, lots of stuff happens and it is usually very impressive to watch. Sometimes we stop tanks on purpose to show for example the development of Ekman layers, but sometimes we are just done with an experiment and then get to see cool stuff to see just as part of […]
One of the first exercises Torge and I plan on doing with the students in our “dry theory to juicy reality” project is to bring a water-filled tank to solid body rotation and measure rotation, surface height at the center of the tank and the sides, as well as water depth before rotation, and then have […]
Lots of demonstrations being prepared for Torge’s and my “dry theory to juicy reality” project. Shown here today: rotating vs non-rotating turbulence. Because the only way to really appreciate how amazing rotating flows are is to compare them with non-rotating ones. And not everybody does have a clear idea what non-rotating flows would even look […]
With all the rotating tank experiments I’ve been showing lately, one thing that comes up over and over again is the issue of solid body rotation. On our DIYnamics-inspired turntable for our “dry theory to juicy reality” project, Torge and I came up with a fun way to illustrate the importance of full body rotation in […]
The DIYnamics-inspired turntable that Torge and myself have been working on for our “dry theory to juicy reality” project is finally working well! This is what the setup now looks like (how simple is that?!) and we had an exciting morning testing different experiments! The one experiment that we have been using as test case […]
Yesterday, we combined a thermally-driven overturning circulation with the effects of rotation, and thus created a Hadley cell circulation. And while the tank was turning faster than we would have liked, we still managed to create a circulation that largely resembles the sketch below: An axially-symmetric overturning circulation (with cold water, indicated by blue arrows, […]
Setting up an overturning circulation in a tank is easy, and also interpreting the observations is fairly straightforward. Just by introducing cooling on one side of a rectangular tank a circulation is induced (at least for a short while until the tank fills up with a cold pool of water; see left plot of the […]
For our project “Ocean currents in a tank: From dry theory to juicy reality“, Torge, Joke and I are working on building affordable rotating tanks to use in Torge’s Bachelor class on ocean and atmosphere dynamics. When people ask what we need rotating tanks for, the standard answer is that rotation of the tank simulates […]
A pink swirl going across a styrofoam block underneath a layer of yellow water? What’s going on here? The picture was taken in a water tank, simulating the circulation of water masses in a fjord. A fjord is a long and narrow bay, usually with a sill that is separating the bay from the open […]
Ekman spirals — current profiles that rotate their direction over depth, caused by friction and Coriolis force — are really neat to observe in a rotating tank. I just found out that they are apparently (according to Wikipedia) called “corkscrew currents” in German, and that’s what they look like, too. I tend to think of […]
I am a huuuge fan of Wlodek Brühl’s liquid art: Pictures of water sculptures that are created with focus on the tiniest of details, that only persist for milliseconds, but that are captured forever in all their fragile beauty. And I think these pictures are an awesome tool in science communication — I see so […]
It has been a long time in the making, but finally we have a nice fjord circulation in our tank! Pierre and I tried to improve it 6 years ago, Steffi, Ailin and I have been working on it for a couple of days last August, then finally this morning, Steffi and I tried again — […]
Inspired by the article “Affordable Rotating Fluid Demonstrations for Geoscience Education: the DIYnamics Project” by the Hill et al. (2018), I spent a fun Sunday afternoon with my friends Joke and Torge in their kitchen, playing with Legos, water and food dye. Turns out building a rotating table isn’t as easy as we had hoped, because my […]
Let’s talk about zonal jets! They keep popping into my life all the time right now, and that has got to mean something, right? Zonal jets, for all that are not quite familiar with the term, are fast-flowing currents (i.e. “jets”) that move along lines of constant latitude (therefore “zonal”). The occur in the ocean […]
I’d love your input: If your student lab for GFD tank experiments had to downsize, but you had to present a “wish list” for a smaller replacement, what would be on that list? Below are my considerations, but I would be super grateful for any additional input or comments! :-) Background and “boundary conditions” The […]
Can you do a bottom Ekman layer demonstration without a rotating table? That’s the kind of challenge I like :-) The way I’ve previously showed bottom Ekman layers is by spinning up a cylindrical tank on the rotating table until it reaches solid body rotation, adding dye crystals to visualise the circulation later, and then […]
How will lee waves look differently if we are using the asymmetrical mountain instead of the symmetric one? And is symmetry actually important at all or are we just looking at different slopes downstream while the upstream slope doesn’t have an influence on the wave field? After admitting I had only ever used the symmetrical […]
This blog post is meant as guidelines if someone other than me might have to set up this demonstration at some point… Have fun! :-) Setting up the stratification If I am working fast and nothing goes wrong, this takes almost 2.5 hours. Make sure you have enough time to set this up! Filling the […]
This blog post is meant as guideline if someone other than me might have to set up this demonstration at some point… Have fun! :-) Lee waves Lee waves are the kind of waves that can be observed downwind of a mountain in the clouds, or downstream of an obstacle in a current as a […]
A ship that is continuously pulled with a constant force suddenly slows down, stops, and then continues sailing as if nothing ever happened? What’s going on there? We will investigate this in a tank! And in order to see what is going on, we have dyed some of the water pink. Can you spot what […]
When setting up the stratification for the Nansen “dead water” demo (that we’ll show later today, and until then I am not allowed to share any videos, sorry!), I went into a meeting after filling in layer 4 (the then lowest). When I came back, I wanted to fill in layer 5 as the new […]
So you thought filling water into a tank was boring? Not on my watch! This is how we fill up the tank: Through a hole at the bottom. Which leads to a very nice fountain that slowly submerges as the water level rises: …and to tons of nice waves, which are great to observe! Propagation […]
During my last visit to Bergen in August, we set up a nice “dead water” experiment. However, there are nice experiments, and then there are awesome experiments, and since Elin wants to use this experiment in her teaching of the ocean and atmosphere dynamics class, we are going for the latter! So I’ve done some […]
On the coolest process in oceanography. My favorite oceanographic process, as all of my students and many of my acquaintances know, is double-diffusive mixing. Look at how awesome it is: Double-diffusive mixing happens because heat and salt’s molecular diffusion are very different: Heat diffuses about a factor 100 faster than salt. This can lead to […]
My favorite experiment. Quick and easy and very impressive way to illustrate the influence of temperature on water densities. This experiment is great if you want to talk about temperature influencing density. Although it doesn’t actually show anything different from a temperature driven overturning experiment, where circulation is determined by hot water rising and cold […]
It’s pretty impressive when a mountain moves through a stratification and generates lee waves. But what I find even more impressive: The waves that travel behind the mountain when the mountain is long gone. See here: This kind of stuff looks more like a numerical simulation than something actually happening in a tank, doesn’t it? […]
Did you seriously think we’d stop tank experiments with only 2-layer systems? Nooo! Today, the plan was to set up a continuous stratification, which I have been planning to do for many years. After fiddling with the setup all morning (do you have any idea how many fittings on all kinds of hoses are needed […]
The main reason why we went to all the trouble of setting up a quasi-continuous stratification to pull our mountain through instead of sticking to the 2 layer system we used before was that we were expecting to see a tilt of the axis of the propagating phase. We did some calculations of the Brunt-Väisälä […]
Now that we do have a really awesome 12-layer 6-color stratification, we obviously had to do the dead water experiment again. This time we chose to include a not-too-happy-looking Nansen on the ship, too! I love this even more than the one we did yesterday!
And here is another experiment that can be done with the same stratification as the lee waves: Towing a ship to explore the phenomenon of “dead water”! Dead water is well known for anyone sailing on strong stratifications, i.e. in regions where there is a shallow fresh or brackish layer on top of a much […]
Did you guess what we needed the stratification for? Yes — we are moving mountains again! :-) What we want to look at: How a current reacts to an obstacle in its way, especially a current in a stratification. But since it is really difficult to set up a current in a tank, let alone […]
I’m back at my happy place — the teaching lab at GFI in Bergen! :-) Here a quick look at what we’ve been doing today: Filling the large wave tank! With clear fresh water and then salty pink water that forms a layer below. As the pink water flows underneath the clear water, there is […]
The experiment presented on this page is called the “slightly more complicated version” because it builds on the experiment “oceanic overturning circulation (the easiest version)” here. Background One of the first concepts people hear about in the context of ocean and climate is the “great conveyor belt”. The great conveyor belt is a very simplified concept of the […]
“The easiest” in the title of this page is to show the contrast to a “slightly more complicated” version here. Background One of the first concepts people hear about in the context of ocean and climate is the “great conveyor belt”. The great conveyor belt is a very simplified concept of the global ocean circulation, which is depicted as […]
Rotating experiments in your kitchen. Eddies, those large, rotating structures in the ocean, are pretty hard to imagine. Of course, you can see them on many different scales, so you can observe them for example in creeks, as shown below: If you can’t really spot them in the image above, check out this post for […]
A wind stress is applied to the surface of a stratified and a non-stratified tank to cause mixing. This is a pretty impressive experiment to run if you have a lot of time, or to watch the time-lapse of if you don’t. The idea is that a density stratification will make mixing harder than it […]
Explore how melting of ice cubes floating in water is influenced by the salinity of the water. Important oceanographic concepts like density and density driven currents are visualized and can be discussed on the basis of this experiment. Context Audience This hands-on experiment is suited for many different audiences and can be used to achieve a wealth […]
I’ve been wanting to develop a good fjord circulation experiment for a long time now — I wasn’t happy with the one we used back when I was teaching in Bergen, and then 1.5 years ago I talked with Steffi and Ailin who took over the tank experiments in Bergen a while back and we […]
Remember the melting ice cube experiment? Great! If I had the chance to teach an intro to oceanography or some other class where I have time with students over a longer period (these days I am mostly giving one-off workshops), I would actually use the thermal imaging camera to make a different point with this […]
Reposting from Sci/Why “where Canadian children’s writers discuss science, words, and the eternal question – why?” — Have you ever wondered what happens when you put a 13-m-diameter swimming pool on a merry-go-round? Probably not. But I am here to tell you today about what happens when you do just that, and what you can learn […]
You know I like tank experiments, but what I am lucky enough to witness right now is NOTHING compared to even my wildest dreams. Remember all the rotating experiments we did with this rotating table back in Bergen? Those were awesome, no question about that. But the rotating tank I am at now? 13 meters […]
Today I ran a workshop at the MeerKlima.de congress in Hamburg: A congress for high school students, organised by a student committee. The large lecture theatre of the chemistry department at the University of Hamburg was crowded for the opening lecture by Mojib Latif: For my workshop, however, we set a limit of 40 participants due […]
Looking at the picture below, can you guess which experiment I am going to do at the MeerKlima.de workshop? Yep, my favourite experiment — melting ice cubes! :-) And I am obviously prepared for several extensions of the classic experiment should the students be so inclined… Now I only need to get the ice cubes from […]
We’ve been thinking about Coriolis deflection a lot recently (see links at the end of this post). But this weekend, at Phaenomenta Flensburg, I came across a so-called “Coriolis fountain”. A fountain that you can put into spin and that then changes shape like so: Uta, remember we talked about this a couple of years […]
After reading recently that I am being considered the queen of the melting ice cube (aaaaw, thank you!!!), having my movies of the experiment featured in Elin Darelius and Petra Langebroek’s article on “fun in the kitchen”, and hearing that the activity I posted on the “On The Cutting Edge”‘s website using the very same experiment has been […]
And really high order ones, too! On Monday, I showed you a movie on wave generation in Hamburg Ship Model Basin (HSVA)’s wave tank. At the end of that movie, we see that the wave energy is being dissipated by a “beach”. Well, we actually see that some of the energy is reflected in those cute little […]
Rotating experiments in your kitchen. Do you know those Saturday mornings when you wake up and just know that you have to do oceanography experiments? I had one of those last weekend. Unfortunately, I didn’t have a rotating table at hand, but luckily most of my experiments work better than the exploding water balloon time-lapse […]
A wind stress is applied to the surface of a stratified and a non-stratified tank to cause mixing. This is an experiment that Martin and I ran at the JuniorAkademie this summer, but since I posted soooo much back than (just look for the tag “JuniorAkademie” to get an impression of what we did) I feel […]
Eddy in a rotating tank. This is an experiment that Pierre and I ran two years ago in Bergen but that – as I just realized – has not been featured on this blog before. Which is a pity, because it is a pretty cool experiment. Under rotation, vertical fronts with different densities on either […]
When hydrostatics just doesn’t explain things. Occasionally one notices water levels in straws that are slightly above the water levels in the glass. And of course – even though we always talk about water seeking its level and hydrostatics and stuff – we know that that’s how it should be because of the capillary effects. […]
Density-driven flow. The experiment presented in this post was first proposed by Marsigli in 1681. It illustrates how, despite the absence of a difference in the surface height of two fluids, currents can be driven by the density difference between the fluids. A really nice article by Soffientino and Pilson (2005) on the importance of the Bosporus […]
More movies of my kitchen sink. I am really fascinated by the hydraulic jumps in my kitchen sink. I can’t believe I haven’t used this before when I was teaching! Yes, movies of rivers and rapids are always really impressive, too, but how cool is it to be able to observe hydraulic jumps in your […]
By popular demand: A step-by-step description of the overturning experiment discussed here and here. I wrote this description a while ago and can’t be bothered to transfer it into the blog format, so please go and find a .pdf here. This .pdf addresses young children in the first part, and grown-ups in the second part. […]
How to adapt the same experiment to different levels of prior knowledge. In this post, I presented an experiment that I have run in a primary school, with high-school pupils, in a Bachelor-level course and in a Master-level course. The experiment itself was run identically in all cases. However, the introductions, explanations and discussions about […]
A simple experiment that shows how the large-scale thermally-driven ocean circulation works. Someone recently asked me whether I had ideas for experiments for her course in ocean sciences for non-majors. Since most of the experiments I’ve been showing on this blog were run in the context of Bachelor or Master oceanography-major courses, she didn’t think […]
Ha, this is a bad pun. We are modeling the Denmark Strait Overflow – but in a non-numerical, small-scale-and-playdough kind of way. More than a year ago, Kjetil and I ran that experiment with a group of high-school students and when writing a post about a much more sophisticated version of this experiment I realized I […]
How to easily set up the stratification for the salt fingering process. Setting up stratifications in tanks is a pain. Of course there are sophisticated methods, but when you want to just quickly set something up in class (or in your own kitchen) you don’t necessarily want to go through the whole hassle of a […]
The “other” double-diffusive mixing process. After having talked extensively about double diffusive mixing in my courses, I tend to assume that students not only remember that there is such thing as double-diffusive mixing, but that they also remember our discussions on how the process works, and that they would be able to transfer this to processes […]
How to show my favorite oceanographic process in class, and why. As I mentioned in this post, I have used double-diffusive mixing extensively in my teaching. For several reasons: Firstly, I think that the process is just really cool (watch the movie in this post and tell me that it isn’t!!!) and that the experiments […]
On the coolest process in oceanography. My favorite oceanographic process, as all of my students and many of my acquaintances know, is double-diffusive mixing. Look at how awesome it is: Double-diffusive mixing happens because heat and salt’s molecular diffusion are very different: Heat diffuses about a factor 100 faster than salt. This can lead to […]
Confusing students even more by discussing how momentum is being transferred from the tank to the water. As you remember, we are preparing for the Ekman experiment and need to spin up the tank to solid body rotation. We had started discussing how, when observed from the co-rotating camera, particles seem to be slowing down […]
Spinning up a tank until all water particles move with the same angular velocity. Before running the Ekman spiral experiment, the tank needs to be spun up to solid body rotation. Even though the concept itself is not difficult, it seems to be difficult to determine when a body of water has reached the point […]
Tank experiment showing (the effects of) the Ekman spiral. One experiments that has been run in GEOF130 forever is the “Ekman spiral” experiment. A tank filled with water is spun up to solid body rotation on a rotating table. Then the tank is slowed down. The resulting friction between the water body and the tank […]
A tank experiment showing ship-generated internal waves. When entering a fjord from the open ocean by ship, it can sometimes be noted that the speed of the ship changes even though apparently nothing else changed – the wind didn’t change, the position of the sails didn’t change, the settings on the engine didn’t change – […]
A solution for the siphon problem of the fjord circulation experiment. After having run the fjord circulation experiments for several years in a row with several groups of students each year, Pierre and I finally figured out a good way to keep the water level in the tank constant. As you might remember from the […]
A movie of patterns observed in the flow when filling the tank for this experiment. Even though there are tons of scientific things to discuss with this movie, like the different refraction of light in the two layers of different densities, or the filaments, or the restratification processes, I am mainly posting this because I […]
A movie focusing on details of the lee waves in the tank. In this post, we investigated lee waves in a tank in a general way. Here, I want to show a detail of those lee waves: In this movie, the concept of hydraulic control becomes visible. On the upstream side of the mountain, the […]
How internal waves in the ocean can be spotted on the surface. Under certain conditions, internal waves in the ocean can be spotted at the ocean’s surface due to changes in surface roughness or to the movement of floating foam or debris. They can be spotted if half their wavelength is longer than the distance […]
Lee wave experiment in a large tank with a moving mountain. In this previous post, we talked about internal waves in a very simple experiment. But Geophysical Institute has a great tank to do lee wave experiments with that I want to present here (although it doesn’t seem to be clear what will happen to the […]
