THE WAVE at Boot Düsseldorf

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It seems insane that back in January I voluntarily spent time at the “Boot”, a water sports trade show in Düsseldorf with over 250.000 visitors. I was there doing ocean scicomm (check out my Instagram for more information on that), but one of my highlights was definitely THE WAVE.

The wave is an artificial standing wave in a flume that wave surfing and SUPing and all kinds of other water sports can be done on, which looks fun. But even more fascinating — to me — is the wave itself (even though, as you see in the picture above, the wave surfing was quite impressive, too!).

Below, you see some early career wave surfers learning to surf the wave, and you see how it’s set up: A lot of water is pumped very quickly through a flume with a topography that shapes a wave form in the current.

But the best part, to me, is the hydraulic jump at the very end of the flume, where the wave actually breaks back upstream, locked in place, and thus quickly looses most of its energy before the water is pumped back through the loop.

And that’s what I really want to show you in this blog post: That standing waves break in the upstream direction (which I find super counter-intuitive). It’s kinda like the stunt where people run up a wall and then do a backflip: The current runs up a slope and gets slowed down and bunched up into a wave which gets so steep that it starts plunging back down onto itself, but is at the same time washed up the slope in an eternal loop (well, eternal or until they switch off the flume ;-))

So here we have it: The perfect example of a standing wave, showing its weird upstream-breaking behaviour! (and anyway: if it was breaking downstream, it would just be flushed away with the current anyway…)

Broken water pipes

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So yesterday this happened: When I was on my way to meet my friend for a run early in the morning, the whole pavement was flooded (look at the cute little hydraulic jumps!). After calling the authorities (and judging from the telephone operator’s voice, I wasn’t the first one! But then how should I know at 6 in the morning when there is nobody else around?) I took a couple of pictures.

There was a lot of water, some of which the storm drains managed to catch.

Luckily, I know where the storm drains lead to — via a little stream and a little lake — right into Kiel fjord!

Below, we are looking down from the sea wall into the fjord. Towards the right, you see the turbulent outflow from the storm drain into the fjord. And then on the left you see curtains of where the mud concentrations change! That’s what I was hunting for when I went down to the water — spots in which the muddy water could be used as flow tracer!

When we walk a bit further to the left, similar curtain pattern are still clearly visible, as well as turbulence behind that rock.

And even more clearly in the picture below: Interesting how there are pockets of clear water are persisting in the muddy waters, isn’t it? Even though the plume of muddy water is spreading, and is being slushed back and forward with the waves on Kiel fjord.

And this is the outer edge of the plume. I love how we can still see that the plume’s mud concentrations varied over time, with the water that came first being pushed furthest out from where the water enters Kiel fjord, and then newer water forming layers inside it.

Sorry about the weird lighting in the picture below, but you see well the record of mud concentrations in the plume:

Even cooler when you go to the other side of the plume: here the plume interacts with rocks and algae to form mud wakes!

I don’t think I’ve fully figured out why they look the way they look, or in general, why the plume is looking so different on this side. Any ideas?

A beautiful #friendlywaves from Spain

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A reader of my blog, Rocío*, sent me this beautiful image from Arnao beach (Castrillón- Asturias-Spain), and I asked if I could use it in a #friendlywaves post. He agreed, so here we go!

First, let’s check out the original image in all its beauty, before I start scribbling on it. What features of the waves stand out to you that you find especially interesting?

For me, what I think is especially awesome here, is how the behaviour of the waves lets you draw conclusions about the sea floor underneath. Look at all the wave crests coming in nice and parallel. Far offshore, it’s difficult to even see wave crests (marked orange, for example), only when they come closer to the shore and the sea gets shallower, they start to build up, get a distinct shape. Yet in some places they become a lot steeper and start breaking a lot further offshore (red marks) than in others — why?

Because in those spots the sea is shallower, thus the interaction with the seafloor is a lot stronger. If you look at the yellow mark, for example: Offshore of it the wave crests are still very shallow and not pointy, and then all of the sudden they break. Here the water is deep until there is a very fast change and then it’s suddenly very shallow (and probably rocky, hence all the turbulence).

And then, if you come closer towards the shore, there is an area that has only a very gradual incline, where the shape of the waves hardly changes any more (blue marks).

And then there is a small inlet to a large puddle that acts as “slit” (albeit a fairly wide one) and lets waves radiate as half circles from where they enter through the slit.

I love how in such a beautiful image of such a beautiful landscape, there is so much physics that we can discover if we only choose to look! :-)

*I asked how I could credit the picture to Rocío, but he doesn’t have Twitter or a website and wrote “I only want you to explain it for people i love your blog and your information you are doing a great job”. Aaaaw, thank you!!! :-) And thanks for sending me this beautiful picture!

Love this #scicomm idea! #MoreThanWeeds

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The hashtag #morethanweeds popped up in my Twitter timeline yesterday (thanks to @aturealexk). I didn’t think about it much because I was participating in #birdrace (shoutout to my awesome virtual team GEO-Tag der Natur where my colleagues and I jointly saw almost 100 different species of birds within a day) and was busy looking for birds and then trying to figure out what kind of birds they were.

However, #morethanweeds must have been on my mind this morning when, in addition to very many pictures of water, I took this picture of a dandelion growing in a wall, and it stuck with me all day. The idea is that there are tons of “weeds” growing everywhere in urban (and any other, of course) spaces and that a lot of people currently do have plenty of time, some of which they spend going on walks. So why not use the opportunity that they are walking right past interesting plants to a) point out to them that they are walking right past interesting plants (which many of them might not even notice without the prompt) and b) give them a little something about the plant? Even if only a name that they can then go on and google if they are curious, or the realization that, the next time they walk past a similar plant, they might actually know what it’s called, or know where to go back to to look it up, or maybe that it’s a different plant and the curiosity to find out something about it?

One thing I noticed yesterday through my participation in #birdrace was how differently, and much more intensely, I looked at birds over the course of just a few hours. And all that just because someone (hi, Nena!) gave me a reason to. And it didn’t end yesterday, this morning I saw a bird I didn’t know and that I hadn’t spotted yesterday, and I tried to take pictures of it in order to look it up properly once I got home. At least for me, this is the kind of thing that really works to rouse my curiosity!

So tomorrow, I’ll take two things with me on my morning walk: chalk, and my plants field guide!

And I’ll be thinking about how to take this super simple idea and apply it to wave watching… Any ideas, anyone?

#WaveWatchingWednesday

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Reposting all of last week’s posts from my #WaveWatching Instagram @fascinocean_kiel. Enjoy!

Lovely morning with wave watching and all the trees in full bloom. Hope you have a nice day! :)

This very climate-stripe-y looking morning is a great example for different surface roughnesses reflecting different parts of the sky towards us, thus showing up in very different colors!

So despite my Corona hair (almost ready for a buzz cut, I tell you!) I really like this picture. Somewhere in the background is a harbor porpoise, the weather is beautiful, I have my coffee with me. Life is good! I am so lucky to be living in a place where I can go be near water every day without breaking isolation. There are few things that make me as happy as seeing water (although right now on the very top of my wish list: hanging out with my super awesome and hilarious and adorable nieces ❤️). Hope you are all doing well!

Ok, I might be weird. But when I wake up before sunrise I absolutely have to go & watch. And isn’t it beautiful?

#waveriddle for you: What just happened???

#Schmetterlingsflieder. Sieht doch schon fast wieder aus wie Sommer in Kiel!

Criss cross pattern due to waves being reflected on the sea wall, plus wakes of those three ducks. So much #wavewatching in one picture!

#SciComm at a #campsite? What a great idea! People are not in a hurry and most likely happy for something stimulating to think about! Like why does the water have different shades of blue, both right now and from day to day?⁠
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On my blog, I discuss a recent article by Woolman (2020) on why campsites might be a great place for scicomm. Check it out this #SciCommSunday!⁠
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This picture was of course not taken recently, as campsites are currently closed down. But here at @localwindheroes in Klein Waabs both I and some of my favourite @KiSOC_Kiel colleagues have done scicomm and our verdict? Works great, should be repeated! Until then we look forward to summer and re-opened campsites!

I love watching the play of light in the waves and on the sea floor. Here showing beautifully how wave rings radiate from where the larger rocks break the surface.

Is this Day 2 of @biologiedidaktikerin-approved summer in Kiel?

Only if you look very closely can you spot that seagull’s wake in the choppy waves today

Windy sunrise today, and a great example of how the water’s surface needs to be at the exact right angle for the sun to be reflected towards us

With windy days comes one of my favourite phenomena: a foam stripe running parallel to the sea wall. But not right at the sea wall, but at some distance to it. Very fascinating! :)

Brine rejection and overturning, but not the way you think! Guest post by Robert Dellinger

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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 kitchen oceanography stuff I have ever posted! Congratulations!).

Robert is using red, warm water on one side and melt water of blue ice cubes on the other side to provide heating and cooling to his tank to create the overturning. Why did I get so excited? Because of this: the head of the meltwater plume was very clearly not blue (see above)! Rob kindly agreed to write a guest post about these observations:

“I first and foremost want to start off by thanking Dr. Mirjam Glessmer for doing a phenomenal job at SciCom through Kitchen Oceanography. I was able to replicate her physical oceanography experiment regarding oceanic overturning circulation for my oceanography class with Dr. Tessa Hill.

As mentioned in her previous post, oceanographic currents are often simplified to give an easier understanding of how oceanic overturning circulation operates. The top 10% of our oceans are controlled by wind-driven currents and tidal fluctuations while the bottom 90% of our ocean currents are controlled by density-dependent movements.Originally this process was defined as thermal circulation but was later expanded to thermohaline circulation. Thermohaline circulation is dependent upon both temperature (thermal) and salinity (haline.) These density-dependent reactions occur when either freshwater fluxes meet saltwater and from thermal differences in water masses. Due to differential heating in our planet, colder formations of dense water masses are formed at the poles, which in turn causes the convective mixing and sinking of water masses driving oceanic circulation.

(Video by Robert Dellinger; thanks for letting me use it!)

In this experiment, we primarily focus on the thermally dependent reactions between two water masses. As seen in the video, the warmer water mass is dyed red, while the cold water mass formed by ice melting, is blue. As expected the more dense water mass (cold) is pushed under the warmer mass once they meet. One feature I would like to point out is the clear plume head feature in my experiment (see picture on top of this post). My theory is that part of the ice cube that was not dyed melted first and was pushed under the warm water mass. This feature is most likely due to the ice cube experiencing unequal cooling, which in turn led to an uneven dye distribution as seen in the previous post “Sea ice formation, brine release, or: What ice cubes can tell you about your freezer.”

As seen in the experiment, thermohaline circulation is thermally driven therefore, the role of salinity causes the system to be non-linear. Salinity serves as a positive feedback mechanism by increasing the salinity of deeper water and strengthens the circulation. Furthermore, current studies are focusing on how atmospheric warming is altering thermohaline circulation attributed by increases in ocean heat absorption and freshwater fluxes (primarily from melting ice caps.)”

Using campsites for scicomm

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Last summer at the Science in Public conference in Manchester, I heard a talk by Anna Woolman on science communication in campsites. It stuck with me as a really good idea. Now I came across the recent article by Woolman (2020) on that study that I found so inspiring, so here are my thoughts on it for you!

Reaching non-specialist audiences and engaging them with science at an affordable seaside campsite

The idea behind the study is that while science days and science festival and those kinds of events are great opportunities for the interested public to engage with cutting edge research or other interesting science, the problem is that it will only engage the interested public. As long as people have to choose to specifically enter a space (whether physically or on the internet) where scicomm happens, doing so actually needs to be made a priority. A priority in how time and money are spent, and in competition with many other things that might be a lot more important to people. So how can people be reached without relying on them to make the effort to enter in a scicomm space?

In this study, the scicomm topic was “insects as a sustainable food source”. The way they did it was a pop up kitchen in the middle of a campsite where they offered a menu made from insects as well as information and conversations on that topic. And here is what they recommend:

Affordable campsites

In the study, an affordable campside near the seaside was chosen in order to reach audiences who might not make an active effort to engage with science otherwise. The assumption that those audiences are more likely to be found on affordable, local campsites than in high-end holiday ressorts is grounded in literature.

(Also, a campsite can provide infrastructure that will make your experience as scicommer a lot more enjoyable. Parking spots, toilets, food, all within easy reach…)

People have time

In the study, Woolman found that since people were on vacation and had time, engagement wasn’t just the sadly too common “grab and go” of scicomm giveaways, but that extended engagement (longer than 10 minutes) could easily take place. This is important because other scicomm activities that take place in spaces where people just happen to be are often in very busy places like shopping malls or even train stations, where there is a lot of people going through, but where engagement is made difficult because people are there for a specific purpose which they want to get done and then go some place else. At a campsite, on the other hand, people have a lot of time on their hands and are often grateful for some kind of unexpected stimulation or the opportunity to have the kids kept busy for a couple of minutes.

School holidays or a weekend in November?

Depending on who your target audience is and what type of engagement you are going for, it might  be a good idea to do your scicomm activity during the busy times. For example during the summer school holidays, camsites are typically most busy, with all sorts of people. If you were to target families with school-aged kids, for example, this would be the time to do your activity! But of course it’s also possible that your target audience are pensioneers — then maybe choosing a weekend or even week day outside of the school holidays might be a better idea! It might not be as busy in total numbers, but the density of your target audience might be relatively higher.

So what now?

I really like the idea of doing pop up scicomm at campsites. At my friend Sara‘s windsurfing school, this was happening when both she and other Kiel Science Outreach Campus (KiSOC; I was the project’s scientific coordinator at that time) PhD students did scicomm on their projects on the beach (in the picture you see a 3D movie on water striders being test-watched). Another project was related to sunscreen — very appropriate to do this on the beach! And from that experience doing scicomm specifically at that place, but more generally in a similar setting was something I wanted to do more of, and that I’ve been thinking about for two reasons.

#WaveWatching

As you know, my pet project is wave watching. And what better place to do it than on a beach? And that beach specifically is great because it offers a variety of features that influence a wave field (Check out a short wave watching movie from that beach here), plus I enjoy hanging out there (which I think is a really important factor when planning a scicomm activity — it needs to be enjoyable! If it’s not, that will show and put people off your science, no matter how awesome it might be).

I’ve been thinking about offering wave watching excursions there and actually had some scheduled this spring and summer, where I would meet up with people, walk to different spots on the beach, and explain what physics they can observe there. Well, there is always next year, or my wave watching Instagram @fascinocean_kiel :-)

GEO-Tag der Natur

I’m the programme manager of the german “GEO-Tag der Natur” festival on biodiversity. As part of my job I’ve been thinking about engaging different audiences through new formats, and this seems like a great idea. For GEO-Tag der Natur, there are typically excursions into interesting biotopes where experts on that type of biotope explain animals and plants that can be found there. Usually we advertise excursions in spots that are especially interesting in terms of biodiversity, but even just a regular beach, forest, or nature around wherever the campsite is located are super interesting and there is so much to discover anywhere! So using campsites as home bases for our excursions is definitely something that I want to try when it’s possible again. It’s also an attractive idea for the campsites themselves to be able to offer these kinds of events, so it’s a win-win!

What are your thoughts on doing scicomm on a campsite? Let me know!

References:

Woolman, A. (2020) ‘Reaching non-specialist audiences and engaging them with science at an affordable seaside campsite’. Research for All, 4 (1): 6–15. DOI https://doi.org/10.18546/RFA.04.1.02

#WaveWatchingWednesday

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Here are all of last week’s #WaveWatching Instagram posts for you! If you would like daily wave watching pics rather than weekly digests, follow my Instagram @fascinocean_kiel!

#wakewatching in a beautiful sunrise. How much better does it get? Love the delicate feathery structure of the wavelets, forming the V-shaped wake with the birds at their tips!

#KielLiebe

Beautiful morning made even more beautiful by those birds’ wakes.

I love the early mornings when the birds are waking up at dawn, before the sun comes up. And the anticipation of wave watching as I am walking down to the fjord :)

Beautiful wakes in best wave watching conditions: very low light source, high contrast, one distinct source of waves (ok, two, but you know what I mean!). Getting up so early is really worth it to me!

I love how in the calm water and sunrise a wave field (wake from a far away ship going through the locks at Kiel canal) and its reflection make this beautiful pattern! Early mornings are the best!

Easter Sunday morning at 6? Mirjam went to make a seal movie for @fraubioke (before other people wake up!) but ended up #wavewatching. Doesnt’t this seal have a beautiful wake?

A beautiful #sunpillarbefore sunrise for Easter Sunday morning! Sun pillars are quite rare, because they only appear under specific atmospheric conditions, when there are small ice crystals in the right spot at the right time. Combine that with the beautiful criss cross wave pattern, and I am very happy!

Usually the criss cross pattern of incoming waves & their reflections make me really happy. But see how much more difficult they make it to see the swan’s wake?

Interesting to see so many different wavelengths at once!

Making waves!

Funny how spoilt I have gotten over the last weeks. Now a morning like this feels almost disappointing. Until I realize how lucky I am to be getting my daily dose of Vitamin Sea in despite everything. Hope you have a good day!

Guest post on “A little bit of lee wave math” by Jeannette Bedard

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Today’s guest blogger Jeannette and I “met” on Twitter when she reposted one of my 24 Days of #KitchenOceanography posts, saying “A friend just forwarded me a #kitchenoceanography experiment that pretty much sums up my MSc work minus all the math.”. So I — obviously — asked her to write a guest post, and here we go! Thank you, Jeannette! :-)

“Lee waves are everywhere. They lurk in your sink, form over mountains and even beneath the ocean’s surface (no doubt they’ll be found out space too).

Mountains and under-sea ridges change how a fluid (air or water) passes over it. Glider pilots in the 1930s first noted the effects of lee waves—when a glider catches a lee wave, the unpowered aircraft can climb higher and stay in the air longer adding to the fun of their flight. But since I’m an oceanographer, I’m going to focus on water.

When water pushes up and over an obstacle, it gets squeezed and speeds up. At the bottom the water slows creating a wave on the surface. How this wave moves depends on the fluid velocity and water depth which can be combined in the Froude number.

The Froude number equals the fluid velocity over the square root of gravity times water depth (note—it’s water depth, not obstacle height so it still applies to the flat landscape of your sink). By using this number, flows in dramatically different settings can be compared. For example, atmospheric flow over a mountain range can be related to water moving over a weir.

So what does the Froude number tell us?

When F is smaller than one, flow over the bump is ‘subcritical’. The resulting surface wave can travel upstream, meaning that downstream conditions affect the flow upstream. This is kind of like tossing a pebble into a flowing stream and seeing the resulting ripples move both upstream and downstream.

When F is larger than 1, flow is ‘supercritical’ meaning no surface disturbance can travel upstream. Here, ripples created by a pebble tossed in cannot overcome the speed of the water and only move downstream.

Now, back to flow over a bump (although the bump is not actually required). As subcritical water pushes over it’s squeezed as the water is now shallower but the same amount of water has to move through. This forces the water to speed up and transition to supercritical.

As faster water crosses over to the other side of the bump where it’s again deeper. It abruptly slows and waves form. Since the water is moving too fast to let the waves move upstream (because it is supercritical) these waves build up, forming a sudden water level increase that can stand still in the flowing water. This is called a hydraulic jump—a non-linear effect observable in a kitchen sink or in water passing over a weir.

The bigger the Froude number is, the more pronounced the jump will be. For flow speeds slightly above the critical speed, the jump forms as an undulating wave. When flow speed increases, the Froude number also increases, and the transition becomes abrupt in shape. Beneath the wave, water flow becomes chaotic in an effect called turbulence.

Because of the turbulence they create, the sea floor under a lee wave makes great habitat for critters—especially stationary filter feeders, as a buffet of tasty treats whooshes by.”