I have been a bit quiet on here recently, because I had so many exciting projects going on that I did not manage to document them in real time (well, not on here anyway, but partly on my Insta).
One of those projects is on #KitchenOceanography with coffee, where I have compiled a lot of interesting experiments into a postcard. And the postcards arrived yesterday! (Thanks, Vanja, for picking them up!)
My super cool new postcards in front of the first slide of my presentation, because I had to take a picture when they arrived and that was the only background available :-D
Juuust in time for the “Hammer talk” presentation that I was scheduled to give at the Geo department of the University of Oslo. Where — you guessed it — I invited people to play with coffee!
Lots of things happening in coffees everywhere!
And I was so excited to see how well people played, and how beautiful the stratifications turned out!
Diffusive layers formed by double-diffusive mixing in a milk-coffee mixture
Here is even an internal wave on the stratification!
I thought I had posted the picture below some time in winter already, but when I recently searched for it, I couldn’t find it. So either I didn’t post it, or I didn’t post any sensible search terms with it, in any case: It’s useless. So here we go again.
Below you see two tea bags that were placed into cold (left) and hot (right) water at the same time. On the left, the tea is sinking down in streaks, while at the same time on the right everything is completely mixed through and through, showing how molecular diffusion depends on the temperature. Which is why we usually make hot tea.
Funnily enough, as I was about to write this blog post and had the picture already open on my laptop, I felt thirsty and decided to prepare a cold brew tea, which you see in the picture below. Here again you see the tea spreading from the tea bag, but it comes out in those plumes and only slowly diffuses throughout the whole carafe.
This would of course be easier to see had I chosen a white background, but since I am still so touched that my friends showed up at the train station with a flower and a flag on Friday, and also since this is literally the spot I put the tea down after I had prepared it, you get to enjoy a view of my flower and flag!
Also that fake flower on the left makes for really interesting reflections on the carafe. Especially the top two that are joint in the middle!
When you post pictures of your* coffee on social media, the coolest things can happen!
Yesterday I got a copy of this Chinese oceanography textbook for pupils in the mail. It’s called 探海观澜：海洋观测的奥秘 (“watching waves and exploring the ocean: the secret of ocean observations” — how cool a title is that??) and it’s featuring a picture of diffusive layering in a coffee that I took! I am so excited! How awesome is it to see my coffee in a Chinese textbook? This will definitely come up as anecdotal evidence in all conversations about the usefulness and reach of science communication on social media from here on onwards!
Thank you, Zhiwu Chen, for reaching out and giving me this super cool opportunity! The book will definitely live in a place of honour among my oceanography-themed books! And I am very much intrigued about the context of the picture (I spot salt fingering and more double-diffusive mixing on the same page) and the rest of the book. I wish I could read Chinese!
*Actually, I think it was @chirinegramke‘s coffee and I just made her let it get cold because the layers were so cool and I wanted to take the picture ;-)
A “fortune teller” for #WorldOceanDay! What would you work on if you were an ocean scientist? And if you are an ocean scientist — are you doing the work you were destined for? ;-) Your favourite drink can give you the answer!
Click on the image below to download a printable .pdf, and find out!
I would really appreciate it if you could give me a 3-minute feedback (click here!) so I can improve future versions of the “fortune teller” as well as my science communication in general!
For some reason my workflow regarding all things #KitchenOceanography and #WaveWatching changed at the beginning of this year. I started editing frames on the pictures I’m posting on Instagram, and, since I was most likely doing this on my computer anyway, scheduling the posts through a program on my computer, which meant that I was typing captions on the computer, too, writing a little more. But somehow that meant that I had already written everything I wanted to write about the pics and didn’t feel the urge to blog later, so … I didn’t. Until now, that is!
Here is a collection of my Instagram posts on coffee in #KitchenOceanography!
Enjoying your lazy first morning coffee of the year (or already back from your New Year’s morning walk, but forgot to take pictures — what’s wrong with you, 2021?)? Then it’s a perfect opportunity to look at wind-induced currents in your coffee! Gently blow across the cup and observe how two counter-rotating eddies develop. This becomes especially clear if you take milk in your coffee (or something else that creates a surface film). Enjoy!
Maybe not The Best Thing about morning coffee, but definitely very important: Observing what happens when you pour milk or cream in! Here the cold milk is denser than the coffee, so it sinks down to the bottom of the glass (it would probably even shoot to the bottom of the glass if it was the same density as the coffee since it’s coming in with a lot of momentum). Hitting the bottom, it shoots along the curved rim of the glass and up in these cute little turbulent billows. But eventually, it will settle on the bottom of the glass, forming a denser layer under the less dense coffee — that’s what we call a stratification, both in density and in coffee&milk. And it’ll stay like that for a little bit, until other processes come into play. So stay tuned for those :-D
Actually, not only internal waves, but also current shear! When you pour milk into coffee, the milk will form a layer at the bottom of the coffee. Similarly to when you poured the coffee in and it surface leveled out, the surface of the milk wants to level out. And similarly to the waves that you probably observed initially on the coffee when you poured it in, waves appear on the interface between milk and coffee. Except that these waves have larger amplitudes, move more slowly and persist for longer. That is because the density difference between milk and coffee is orders of magnitude smaller than that between coffee and air. Those waves are called “internal waves”. And what we see in the pic, too, is that the milk layer is moving relative to the coffee layer, therefore the wave crests are being pulled into these sweeping strands. Pretty awesome!
My sister & nieces made this mug for me for Christmas. Isn’t it just perfect together with the swirl in the last bit of my coffee? I’m considering making this my logo and profile pic and EVERYTHING because I think it is Just. Perfect.
I’ve been playing around with different glasses and different ways of lighting them in order to get clearer pictures of the things I want to point out: The behavior of the fluids, not reflections on the side walls of the tanks I am using. At least here there are only two stripes where the light is reflected? And the internal waves on the interface between milk at the bottom and coffee on top come out quite clearly. Even from this photo you can see how dynamic the system is!
Again, there is a milk layer at the bottom of the coffee. And those mushroom-y milk fingers appear when the milk is warming up and its density is thus decreasing. As it gets less dense than the coffee, the stratification becomes unstable and milk starts rising until it reaches a level of its own density.
Today there is some interesting surfactant on my coffee. It might be due to oils in last night’s tea that I didn’t clean off, or maybe it’s the cream (but I would think that that’s the little blobs of oil you see). In any case, the surface film behaves in very interesting ways: It is showing us a front in the coffee, with lots of small instabilities on the front! The front must be related to me drinking from the mug somehow, but I’m not sure how. Thanks to the surface film, we also see convection occuring in the top left, where we get all those small-scale structures in the color, lighter areas indicating convergence zones where the surface film gets pushed together, darker areas where it is pulled apart.
A little while ago I posted a picture of the front you see in my coffee here. And what I did then was twist the mug a little bit: I wanted the front to be in the picture more nicely together with the little boat. BUT: exciting things happened (predictably): As I was twisting the mug, it did not behave as a solid body together with the coffee. Rather, it twisted while the coffee was not! And this created shear between the sidewalls of the mug and the coffee, which is what we see all around the edge: shear instabilities breaking into eddies! And all that due to inertia of the coffee.
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 and prepare … Instagram posts (did I mention I asked that question on Twitter? Yeah. Don’t ask me about the logic behind that). Anyway, below is the beginning of that series (which, on Instagram, is not posted consecutively, in case you are wondering about how often people want to see me grinning at the exact same experiment…). Enjoy!
So people tell me they want to see more #KitchenOceanography. Get ready for 2021, I come prepared! Carrying a non-alcoholic experiment with me (doesn’t look like it, does it?). Can you tell which of the glasses contains salt water and which fresh water? Both were at room temperature before I put in the (now mostly melted) ice cubes… Happy New Year! May your 2021 be full of curiosity and new experiences!
What do I love so much about #KitchenOceanography? Discovering oceanography EVERYWHERE. . When people think of oceanography, they think of endless oceans, weeks and weeks at sea on research ships, something that feels remote and unconnected to their everyday lives. But for me, it is anything but! And #KitchenOceanography is a great tool to bring the ocean and a normal everyday life closer together, both for myself and others. The concept of #KitchenOceanography is simple: you use what you find at home to simulate oceanic processes. Usually this involves some kind of “tank” (anything from a tupper ware container to the wine glass as in the picture), obviously water (usually varying temperature or salinity to change density), food dyes (or anything that can safely be used in food storage containers and that can act as coloring, e.g. dark red fruit juice, black coffee, …). And then you put it together, observe, and relate the physics happening in your kitchen to the things that happen on much larger scales in the ocean. Fun! #KitchenOceanography works really well as a fun activity at home, but is also a great tool in teaching, both in-person and remote. Over the next couple of posts I’ll tell you how and why to use it, and give you plenty of ideas for #KitchenOceanography experiments, so please check back!
It might not be immediately obvious to you why I am grinning stupidly at the camera in the picture above, while holding green ice cubes over two glasses full of water, so let me explain. I am about to drop the two ice cubes into the two glasses of water. But those two glasses are not filled with the same stuff. Even though it’s water at room temperature in both, one is fresh water and the other one is salt water at approximately a typical oceanic salinity (e.g. 35g of salt per liter water, or 7 tea spoons per liter). When the ice cubes are dropped into the water, they’ll both melt (in fact, they have already started, which is why I had green finger tips for days after this picture was taken). But they won’t melt in the same way. I’ve done this experiment dozens of times, alone or with people from preschool age to professional oceanographers, so I know what will happen. But what I don’t know is what EXACTLY it will look like, and what I might discover for the first time, or see more clearly than before. Even though the experiments are simple, there is ALWAYS something new to discover, because even such a simple system is still chaotic. Plumes of melt water will never look exactly the same, nor will the condensation on the glass. Discovering all those small featuers and contemplating the physics behind them makes me happy, and it’s easy to engage most people once they get over the “you are looking at two ice cubes and two plastic cups!?” threshold and actually start observing, questioning, and trying to explain, which is why #KitchenOceanography is such a great tool in teaching & outreach!
Eliciting! . #KitchenOceanography is a great tool in teaching and outreach of ocean and climate topics, because we are using a simple system — one that people think should be easy enough to intuitively understand. But this is often not the case for many reasons, one being that many people have “misconceptions” about physical processes: ideas that they formed and that worked well to explain their observations until now, but that aren’t correct and that will break down in the context of the physics we are trying to teach. . But in order for those misconceptions to be changed into correct understanding of physics, they first need to be brought to light and be made conscious. . For example by asking: In front of me you see two glasses, one filled with salt water, the other with fresh water, both at room temperature. If I drop the ice cubes in, which one will melt faster, the one in fresh water or the one in salt water? . At this point, it is not important that students give the correct answer, but that they articulate their beliefs. And what happens next? Look out for my upcoming “confront” post!
Confronting! In my previous “eliciting” post, I talked about the importance of realizing WHAT it is that we believe about how the world works. But what if our beliefs are wrong? Then, #KitchenOceanography is a great tool to confront a prediction of what SHOULD happen with what actually DOES happen. It’s surprisingly difficult to observe something that is not what we expect to observe! But when we manage to make observations that contradict what we expected to see, we come to the “confronting” step: Realising that there is a conflict between our interpretations of the world and how the world really works. So what now? Look out for my upcoming “resolving” post!
Resolving! . In previous posts, we have eliceted a misconception by asking what we believe would happen in an experiment and making predictions about the outcomes. We then confronted our prediction with an actual observation. . Now we need to somehow resolve the cognitive dissonance — what we thought should happen did not happen — and build new, correct ideas about physics into our belief system. This happens best by explaining how things fit together, either to others or to ourselves (I think the main reason I like blogging and social media is because it forces me to explain things to myself, thus helping me to understand them better!). . So this is where we talk through what we observed, what did happen, how we can explain it, what might have happened if the boundary conditions had been different. Another thing that’s great about #KitchenOceanography is that in many cases, it is very easy to test what happens when you change the boundary conditions: You CAN force the ice cubes to the bottom of the glasses and observe what happens, you CAN add salt to the water before making the ice cubes, you CAN change the water’s temperature. And then observe what happens, and see if it fits with what we expected to see. . Of course, once we get playing with #KitchenOceanography, we easily get stuck with it, changing one thing, then the next. So if you use this in teaching, be aware that it will — and should! — take a lot longer than just running an experiment once, and then moving on. But, since the experiments are so easily done with household items, students can always continue discovering outside of class, too; no fancy lab needed! Perfect! :)
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 that investigate different questions. After the cruise, students use the data they acquired during the cruise to write a report on the data.
There are several different aspects that I would like to prepare the students for:
Recognizing and understanding the relevant physical processes they are supposed to investigate
Dealing with the data both onboard and once they get back home
Below, I’m expanding on my thoughts on how to do that.
Recognizing and understanding the relevant physical processes
Let’s look at two typical teams on those student cruises: the “drifter” team that deploys surface drifters and interprets the trajectories later on, and the “CTD” team that takes profiles of temperature, salinity and other properties of the water column and then interprets those afterwards.
Interpreting surface drifter data
In the area investigated during the student cruise, there are several processes that influence which way a passive surface drifter will take, e.g. tidal currents, wind-driven currents, the circulation induced by fresh land run-off, wave-induced drift. Also there might be effects of wind on the drifter (although when designing the drifters, care was taken to minimize the effect) or of other processes. The relative importance of those processes is not necessarily clear beforehand (or even when looking at the data), and it is most likely neither constant in time nor in space. So even though it seems like it should be simple enough, it’s not an easy task!
Additionally, even though students are theoretically familiar with some of the processes, their familiarity is mostly restricted to theoretical considerations of ideal cases, not with messy mixtures and real-life cases. So my suggestion would be to help them familiarize themselves with these processes, for example like this:
First: help them realize that there are many many many processes happening simultaneously
One way to do this is to provide a picture that shows many different things at once and ask students to annotate it with a certain number of processes they can spot. Knowing that there are at least four (or however many) processes to discover in the one picture they are given gives them confidence to name at least that many, or to keep looking until they’ve found that numer.
I usually use a different example, but since tomorrow is #CTDappreciationday and I’ve been looking at old CTD pics, I thought I’d give you a new one:
In this picture of a submerged CTD, we see any different processes, for example looking at waves: a wake-like wave where the CTD wire has been cutting through the water as the ship moves relative to the water, the splashes that happen when drops from the crane fall into the water and the little crowns they form, how the waves spread as rings from the points of impact, how different waves are supperposed and the interference pattern they form. Or ALL the optics of light going in and out of water: how shapes appear deformed, how colors change, … And many more!
Obviously it would be advisable to chose a picture that shows processes related to what the students are supposed to investigate.
Second: ask them to observe a given location and observe and describe as many different (or three, or five) situations as possible
This task is similar to the first one, but not having the reassurance that there are so-and-so many processes visible at the same time makes it a little more difficult. But it’s a great exercise to try and find as many different things going on in a system, because it will later help them to think of processes that might influence their observations.
Third: ask them to go & discover a process “in real life”
Now that students have seen that life is messy and processes aren’t usually occuring in isolation, but are superimposed on or interacting with others, they are ready to go find a process in real life. To prepare students of the drifter group, useful tasks could be to find (and document) instances of
a tidal current (and how do you know it’s a tidal current and not just a regular gravity-driven current like in a river? You might have to come back at a different time, or relate the current to tide tables)
wave propagation and current direction not being aligned (since surface waves are a lot easier to observe than current direction, it’s easy to assume they are always in the same direction. They are not!)
land run-off forming a buoyant (and possibly differently colored) plume in saltwater (or any other water forming a plume in a larger body of water, e.g. a storm drain going into a lake)
Even if students might not find the exact process you were hoping for, that’s ok! They will probably have an explanation for why their replacement is a good one, and that means that they put some thought into it, too.
Four: ask them to observe (some of) the relevant processes in real life and collect data
I find it a very useful exercise to try and collect data on a phenomenon without any proper equipment. For example, a tidal current can be related to the position of buoys within it, or the tidal elevations can be estimated by repeatedly taking pictures of the same pylon of a bridge. And then, of course, plot the data and discuss it!
It might seem like busywork, but I would argue that it really helps practicing observational skills. And they are going to appreciate instrumentation so much more once they get to work with it later on! :-)
Five: relate it to what to expect at sea
This is the really difficult part. From their short cruise, students will come back with a data file full of numbers, i.e. the positions at the drifter at a given time. How does that relate to what they’ve been observing until now?
Well, the idea is for them to come back with so much more than just the one data file with drifter positions. Ideally, since they know how messy the system is they are about to interpret, they’ll come back with data on the wind field (either from what the atmosphere group measured, or from the regional weather forecast), with data on the tides (from tidal gauges in the area, or models), with observations of wave height to calculate Stokes drift, with observations of anything unusual (like once when one of our drifters got caught by a ship and displaced). Ideally, all the practices we did beforehand prepared them to realize that they will want to have all this data, even if only to exclude the influence of one or several of those factors.
Ok, so much for our drifter group. Now on to the CTD group!
Interpreting temperature & salinity profiles
Temperature and salinity profiles have arguably been the most important type of oceanic data in the history of oceanography. They are also not something that is easy to come by, because you typically need a ship and some instrumentation to measure them. But there are still ways to help students familiarize themselves with the idea of temperature and salinity profiles in a practical way before their cruise.
First: help them realize that there are many many many processes happening simultaneously
Temperature and salinity profiles are really difficult to interprete because there are SO MANY things influencing them! A really good way to realize that is by asking students to do a simple overturning experiment and draw profiles over time in fixed location.
In the very simple overurning experiment, T and S profiles could look something like what’s sketched in above. The red dye is heated (in order to make it buoyant enough to stay on top and mark the surface flow). I’m writing “S” in quotation marks, because I’m lumping both red and blue dye together as “something dissolved in water”, which I abbreviate as “salinity” for this purpose… And of course, all the overshoots in S don’t make sense, as I realized when I couldn’t be bothered any more to draw it again… But a good point to discuss, maybe? :-D
Here we see that it’s not just the cooling driving a circulation, we also see salt fingering occurring as the red dye cools and thus becomes denser than the clear water at the same temperature. So even in such a simple experiment there are different processes happening at the same time!
Second: ask them to observe a given location and observe and describe as many different (or three, or five) situations as possible
Same as I suggested for the “drifter” group, possibly with a focus on processes that influence temperature and salinity (river runoff, rain, evaporation, mixing by surface waves, parts of the body of water that are in the sun vs shade). The point is not necessarily to find the most relevant process, but to recognize which processes might potentially have an influence (even if minuscule) and thus make interpretation of observations more difficult later on.
Three to five
The temperature and salinity profiles are influenced by similar processes as I described for the drifter group, because they are shaped by advection of water with different properties and from different directions. So trying to observe the processes described above makes a lot of sense here, too! As do the other steps I described above.
But now how do we prepare students to cope with the data once they are back from their cruise?
Dealing with the data
Students are provided with finished programs that read in and plot the data, that they only need to modify if they want to show things in a different way. Yet it’s surprisingly difficult for them to manage that when they come back from the cruise.
There are several aspects to dealing with data that we can help students prepare for:
getting data into the program you want to work with, and making plots
Of course, all of this could be done just by using last year’s data (and actually maybe it’s not such a bad idea to ask students to re-run someone else’s analysis, because then they KNOW it worked a year ago, so unless they changed something, it should be working again now). After reproducing last year’s figures, students could read last year’s interpretations of those figures and discuss whether they agree with them or what they would do differently (obviously this works best if last year’s interpretations are somewhat helpful).
BUT it could also be done using new data that the students generate themselves as part of their observations earlier. For example for the temperature and salinity profiles in the easy overturning experiment, they could use some depth axis and assign numbers to the profiles that qualitatively represent the shape they drew earlier (or, if you wanted to get fancy, you could probably use temperature probes in the tank and get actual numbers). The idea here is not to get data that is as complex as they would get on the cruise, but to get a data file that is similarly structured to the ones they are expecting to get, to read it in, to plot it, and maybe practice to modify axes etc..
What do you think? Any suggestions, comments, feedback?