As you might have noticed, the last couple of days I have been super excited to play with the large tanks at GFI in Bergen. But then there are also simple kitchen oceanography experiments that need doing that you can bring into your class with you, like for example one showing that tides and internal waves […]
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 […]
When we move our wall back and forth, we create very strong wing tip vortices that persist for quite a long time. Above, you see the vortex, lit by a laser sheet close to the surface. You can see the whole column rotating as one, that bright smudge below the swirl is the lower part […]
Different types of experiments, and why we use such a weirdly-shaped “Antarctica” and are happy with it. When we want to show people images of our model experiments in a tank, people often imagine that they will be shown cute little miniature landscapes, looking much like the ones you see for really fancy model train setups. And then they are […]
For all our experiments here on the rotating platform in Grenoble, we have had a source, introducing an artificial current into our water-filled tank. With flow rates between 15 l/min and 60 l/min, and experiments running for about half an hour, that is a lot of water that has to come out of the source! […]
We are very deep into discussing all the different ice shelf experiments that have happened so far. As you see above, the white board in our office is filled with drawings of our interpretations of the experiments. And as you know, things don’t always go exactly as planned. Or, in fact, most of the time […]
We have already described experiments where our ice shelf was tilted, making the setup a little more realistic* than before (link here). But then later that day, we did two more experiments! And this time, the ice shelf wasn’t just tilted, it was also not going up all the way to the surface (or, well, […]
You have seen plenty of images of our experiments over the last weeks (and if you have not, scroll back on the blog!). Time to show you what a day in the Coriolis lab looks like for us! Above, you see Nadine and Adrian watching experiments. For each experiment, we spend approximately 30 to 40 minutes […]
As long as water depth and latitude stay the same, a current usually happily goes straight forward. However, a large part of what we are doing at the Coriolis tank in Grenoble has to do with what happens to ocean currents when they meet topography, so sea mounts, ridges or troughs under the water, and what […]
Until now, we have used an “ice shelf” (a plastic box) which had a horizontal bottom (Read more about the general setup of the experiment in Nadine’s post). The bottom of the ice shelf was either right at the water’s surface, or lowered down into the water. What we see then is shown in the gif below, […]
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 […]
For our scientific analyses, we look at the flow field at several discrete levels throughout the water depth. But we can — just for fun! — look at them almost continuously while the scanner is moving up and down, and that’s what I want to show you today. Isn’t it cool how the flow is […]
At some point the angular velocity of our tank was accidentally changed a tiny little bit. That was almost instantly corrected, however we could see the effect for quite some time later: inertial oscillations! All the water in the tank moved in circular motions at half the period of rotation. You read about inertial oscillations in […]
I’m sure there will be an official press release some time later today, and we will link to it when it comes out, but I thought I should let you all know that yesterday, on Nansen’s Birthday, Elin received the 2017 award for polar research of the Framkomitee. I don’t know what was said in the official […]
What happens when the almost neutrally buoyant particles that we use to visualize the flow field have sunken out of the surface layer? The fairy-dust sprinkler comes and sprinkles more fairy dust! :-) And that produces all these cute little swirls that glow bright green. So pretty! :-)
We’ve talked before how we use the laser to light up neutrally-buoyant particles on horizontal slices of our tank, but we can actually also do this in the vertical. This is sometimes very helpful to check whether the particle distribution is still good enough or whether someone needs to go in and stir up some particles […]
You’ve probably been wondering about this, too: We have a constant inflow from our “source” into the tank. How do we keep the water level stable? Worry no more — here is the answer. In the picture above you see Samuel adjusting the skimmer — a sink inside the tank that height is adjusted such that […]
Just so you don’t get bored over the weekend (and because they are so so beautiful to look at!) here are a couple more sneak peek gifs of our experiments. Remember, though, that what we see are only particle distributions in one layer close to the surface, and also the very beginning of the experiments […]
This blog post was written for Elin Darelius & team’s blog (link). Check it out if you aren’t already following it! — I read a blog post by Clemens Spensberger over at a scisnack.com couple of years ago, where he talks about how ice can flow like ketchup. The argument that he makes is that ketchup […]
A very convenient way to describe a flow system is by looking at its Froude number. The Froude number gives the ratio between the speed a fluid is moving at, and the phase velocity of waves travelling on that fluid. And if we want to represent some real world situation at a smaller scale in […]
When we come back from research cruises, one of the things that surprises people back home is how much time it takes to take measurements. And that’s for two reasons: Because the distances we have to travel to reach the area we are interested in are typically very large. And then because the ocean is also […]
When talking about oceanographic tank experiments that are designed to show features of the real ocean, many people hope for tiny model oceans in a tank, analogous to the landscapes in model train sets. Except even tinier (and cuter), of course, because the ocean is still pretty big and needs to fit in the tank. […]
Similarly to last Friday’s Kelvin-Helmholtz instabilities, observing swirls and eddies made from green fairy dust is not really what we are in Grenoble for. But are they pretty! And it is actually very interesting to observe the formation of eddies. If you look at the picture above and focus on the sharp edge “downstream” of the canyon, […]
When watching the images or movies that show the rotating tank from the outside, you may have been wondering about why the whole structure — tank, office above the tank, everything — is inside a rotating tent, which itself is inside a large room. Remember the last time you were on a merry-go-round? Remember the […]
This is really not the focus of our experiments here in Grenoble, but they are too nice not to show: Kelvin-Helmholtz instabilities! They showed up really nicely in our first experiment, when we only had neutrally-buoyant particles in our source water (and not yet in the ambient water). The water that shows up as the […]
When you see all our pretty images of currents and swirling eddies and everything, what you actually see are the neutrally buoyant particles that get lit by the laser in a thin sheet of light. And those particles move around with the water, but in order to show the exact movement of the water and not something […]
A very common idea of what goes on in our tank is that we have a tiny Antarctica in the center and that the edge of our tank then represents the equator. We are rotating in Southern Hemisphere direction, clockwise when looked from above the pole. And when looking at the Earth that way, where the […]
As you see, we have increased the rotation rate of the tank! From 1 rotation in 50 seconds to now 1 rotation in 30 seconds. Which means that at the edge of the platform, where we get on and off, the difference in speed between the room and the moving platform is 5,6 km/h. For […]
Depending on how strong a current we introduce in the 13-m-diameter rotating tank to simulate the strength of the coastal current in Elin et al.’s 2016 article (link on our blog, link to the article), it takes different pathway along and across our topography. According to theory, we expected to see something like what I […]
After seeing so many nice pictures of our topography and the glowing bright green current field around it in the tank, let’s go back to the basics today and talk about how this relates to reality outside of our rotating tank. Above you see the red arrows indicating the coastal/slope front currents. Where the current […]
Just a quick update from the lab tonight: We are fixing more bugs by the hour :-) First: the bubble-free source. I have previously written about how we thought we were going to get our source bubble-free (link here). Turns out, it’s not quite as easy as we thought — there were still plenty of bubbles […]
You’ve heard us talk a lot about rotating swimming pools. Nadine has written about why we care about Antarctic ice shelf melting (link), why the ice shelf is melting (link) and how we are going to investigate it (link). Today, I am going to bring those explanations together with all that you’ve seen so far […]
Sometimes the devil is in the details… On our first day at the Coriolis platform in Grenoble, I took a picture of the “source” in our experiments (see above): The plastic box that is fed by a hose from above and that has one open side with a “honeycomb” (or: a make-the-outflowing-water-nice-and-laminar thingy, technical term) that introduces […]
Above you see the very first water coming into our tank. Only a couple of hours, and the tank was full! And in solid body rotation (since it has been spinning all the time while being filled) which means that we can start doing the real experiments very soon! :-) Most of the afternoon has been spent testing the […]
This blog post was written for Elin Darelius & team’s blog (link) which you should totally follow if you aren’t already! — We have started rotating and filling water into our 13-meter-diameter rotating tank! So exciting! Pictures of that to come very soon. But first things first: Why do we go to the trouble of […]
Today we have foam patterns again, but of a very different kind than usually: I don’t know if I have just never noticed before (I can’t really imagine I would have missed that?), if it never happened when I have boiled eggs because I always boil my eggs with more bubbles and hence more turbulence, […]
This blog post was written for Elin Darelius & team’s blog (link). Go check out that blog, more cool stuff being added there every day! :-) — Remember this little office on top of the tank? Exciting stuff going on there: Testing of the cameras that were just being installed in the last post! (Of […]
This blog post was written for Elin Darelius & team’s blog (link) and is just reposted here to keep my archives complete. If you aren’t already following Elin’s blog, you should really do it — more awesome blog posts coming in every day! :-) — We have arrived at the Coriolis platform in Grenoble and […]
