Pop-up beach walk

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Strong west winds aren’t the best for traditional wave watching on the east coast, but we got beaches in places where we usually don’t have them! Pretty exciting, especially since I’m on a home office day (luckily the trains to work don’t run regularly because of the storm, so I got to squeeze in some beach time before work!).

Below, you see where the big storm drain runs into Kiel fjord. You might remember it, because it’s the one that the fluorescent dye tracer comes out of whenever the city’s heating systems leak. Except that usually there is a lot more water around here…

So this is a pretty unusual perspective!

Also walking underneath these bridges is usually not recommended.

But it’s pretty cool to see these familiar structures from a very different perspective!

Something I found super interesting about this picture is this little groove that has formed underneath the edge of the bridge. What it shows us is that it has rained a lot at a time when the water was already gone, because that’s how this groove got formed! if there was still water around when the rain ran off the bridge, a) any “impact” of drops would have been dampened a lot by hitting water and b) waves would have acted to remove the groove and shape the sea floor in whatever other way they liked. So fun to discover these things! A bit like playing detective :-D

Maybe rubber boots would have been more appropriate…

Definitely interesting perspectives from down here!

But: Breaking waves on the beach! That’s not something we see a lot around here!

And finally a better look at the obstacle these stilts are there to keep boats off of.

It’s definitely a very different experience to my usual walks along here!

And even some rock pooling today!

#WaveWatchingWednesday

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Here is another #WaveWatchingWednesday with last week’s recap of my wave watching Insta @fascinocean_kiel! Enjoy!

Opening my mom’s fridge, I went „WHAT IS THAT SUPER AWESOME LAYERED SAUCE???“. Turns out this was accidental #KitchenOceanography. The sauce was blended when it went into the fridge, then separated and formed layers. Density stratification!
Unfortunately I have to report that the internal wave experiment (that obviously had to happen!) didn’t go so well, too much damping. Layers just veeery slowly return back to horizontal…

The flood is coming in quickly! Most waves reach further in than the one before did, thus reshaping the look of the beach. Footsteps of dozens of people enjoying their stroll — first just blurred a little, then soon gone completely. Covered in foam, shells, then water. Until, a couple of hours later, the water recedes again, each wave leaving fresh, smooth sand for someone to be the first to have walked on that part of the beach, until the whole beach is covered in footprints again. Am I the only one who finds this strangely poetic?

My sister pointed out the waves from the fountain on the left meeting the wind waves coming in from the right, and that ended up being almost as exciting as a bunch of lambs born only the night before!

Not wave watching, but how cute are these little lambs???

#WaveWatchingFromTheTrain

I really like this view of Hamburg!

Finally! Back home to blue skies and wave watching! Today: seaward winds, thus hardly any waves on this side of Kiel fjord. But can you see the breeze offshore where the sea surface looks rougher?

Sunny lunch break!

Oh a seagull making waves!
But what causes the waves that seem to be radiating from the lower right corner of the picture? Check out the next pic!

It’s other waves from a distant ship ⛵️hitting the corner where the beach meets the seawall and radiating from there!

And that’s it for this week! Have you been wave watching lately? If not, what’s your excuse?

#BergenWaveWatching: Rainbows!

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Reposting from Elin’s blog here!

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Kjersti, Steffi, Elin and myself (Mirjam) recently discussed ways to better integrate the GEOF105 student cruise into the course. My suggestion was to ask the students to observe things throughout the whole duration of the course, and then have them relate their time series with what they observe when “at sea”. In this mini series tagged #BergenWaveWatching, I write up a couple of suggestions I have for observations that are easy and fun to make. I am anticipating that my suggestions will be strongly biased towards #wavewatching, so if you have any other suggestions, I am all ears! :-)

Neither wave watching nor particularly Bergen-specific, but still super cool! And probably as close as I will ever come to suggesting any kind of meteorological observation. Clouds are pretty amazing, too, but I really don’t know enough about those…

Where to go

Nowhere specific, just keep an eye out for situations in which there are water droplets in the air and the sun is low enough in the sky for rainbows to appear. Be aware of where rainbows would appear if they were visible (the shadow of your head would be in the center of the rainbow) and check out if they are there.

It doesn’t actually have to rain for rainbows to appear…

When to go

Since the sun needs to be sufficiently low in the sky for rainbows to be above the ground, rainbows are more likely to appear in the morning and afternoon.

What to look out for

Duh. Rainbows?

What to do with the data

I think it could be fun to try and relate the appearance of rainbows to the kind of weather. Obviously, you need both sun and rain. But for double rainbows, you need several rain fronts behind each other. And for a secondary rainbow as in the picture on the very top (blog post on that here), you need strong sunshine.

The observations suggested here are also well suited for a description of the phenomenon and an explanation of the physics behind it.

How this is relevant for the student cruise

Not directly, but I think getting into the habit of observing something fairly specific and, over time, becoming an expert on spotting and explaining rainbows, is pretty awesome!

Do you have suggestions for us? What other spots or topics would you recommend in and around Bergen to be added to the #BergenWaveWatching list? Please leave a comment! We are always looking to expand this list!

For #SciCommSunday: On the power of hashtags

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Often completely underrated by people who start using twitter: The power of hashtags.

In this post: Very brief intro and then the three main purposes for which I personally use hashtags.

Hashtags: make your tweets easily findable

Marking a keyword in a tweet with the #-sign turns it into a link which, if clicked, takes you to a list of all other occurrences of this keyword marked by the #-sign, too. Hashtags are therefore a great way to make sure your tweets are seen by the relevant audience, or to make sure you see everything anyone else ever tweeted and marked with a specific hashtag.

Hashtags can be very broad (for example #science) or they can be very specific (like my favourite hashtag, #KitchenOceanography). And there is a whole spectrum in between those two extremes. Going from broad to more specific, one could use hashtags like #OceanScience, #Oceanography, #PhysicalOceanography, #OceanographyLab. Each of those is targeting a smaller audience, but one that is probably more specifically interested in what you are sharing (if you are writing about kitchen oceanography). Which hashtags to use therefore depends really on who you want to reach with a tweet: a larger, broad audience or a smaller, more focussed one.

I personally use hashtags for three main purposes:

Finding & building my community using hashtags

#CTDAppreciationDay, on January 22nd, is an amazing example of how social media can bring a community together around a common passion, in this case an oceanographic instrument.

This year’s #CTDAppreciationDay was the 5th annual event of its kind. From what I understand, it was started out of a combination of frustration and boredom at sea (but I might be completely off here. The first mention that I can find and that I am basing my interpretation on is this one here). But no matter why it was started, it definitely caught on: Oceanographers of all disciplines use the instrument, and clearly many people appreciate it a lot. So on this year’s #CTDappreciationday, about 200 tweets used that hashtag on Twitter. Nearly all of those tweets were either reminiscing of a particularly noteworthy moment at sea working with the instrument, a pretty sunset or rough weather, or were showing the many different applications of the instrument.

While those tweets are definitely enjoyable, for me, using this specific hashtag more is about finding “my people” than the content of the tweets themselves. Just following the hashtag #CTDAppreciationDay, I found about 40 new people to follow on that one day. All those people share my passion for fieldwork and appreciation of CTDs, and tweet about stuff related to the oceanography. I also gained 22 new followers that same day plus 19 more over the next two days (can’t be completely sure they all found me via that hashtag, but many of them followed me back after I followed them). As I don’t go to conferences any more, twitter is my main way of meeting new oceanographers, and this hashtag worked super well!

Which hashtag could you use to find “your people” — people that you don’t know exist yet but that share your passions?

Finding relevant tweets to a topic using hashtags

I love lab experiments. #FlumeFriday is a hashtag used on Fridays to mark posts that show some kind of experiment in a flume (a channel filled with water; in oceanography labs typically used to generate waves in or to have a stretch of controlled flow; both often combined with experiments on sediment transport, coastal protection, flows under different conditions). So in short: #FlumeFriday is super exciting for me! And it’s a hashtag that I both follow (because it’s so cool! Also I am always looking to learn more about tank experiments, what people work on in that area, what techniques they use, what their experiences are, …) and actively use (because I know that people following that hashtag are interested in tank experiments, even though mine are usually a lot more small-scale than most other people’s).

Another example of hashtags I follow are conference hashtags, whether I am there or not. For example #OSM20, the hashtag of the Ocean Sciences Meeting 2020,y is one that I will definitely follow since I wish I could be there!

Are there topics for which you would like to be notified each time someone tweets about them? What hashtags would people use for those topics?

Curating a collection of tweets using hashtags

There are two hashtags that I use with my work all the time: #KitchenOceanography (which was actually first used by my friend Geli at a time when I really didn’t know how to use Twitter well) and #FriendlyWaves. Both are super specific. #KitchenOceanography is about the oceanography-related experiments that you can do using only household items (check out posts about that here). #FriendlyWaves are posts in which I explain pictures of waves that my friends sent me.

Over the last months, pretty much all uses of those two hashtags were somehow related to me and my work. Which is really awesome: People who now look at those hashtags because they are curious what exactly is hidden behind those two terms find two projects that I am really passionate about, and also see that I am dominating those hashtags. So in a really positive way, I use those hashtags to “mark my territory”. And if someone else should start using them more frequently, I know there is a great new friendship in the making!

What hashtag is so super specific to your interests and work that you can make it your own, make it part of “your brand”?

Giving it a side eye: Why we use high-walled tanks on our rotating table #FlumeFriday

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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 to observe the vertical dimension. Even though oceanic flows are largely 2D and thus a shallow tank should be enough (and it is for many purposes!), if you look at representations of sections of oceanic properties, the vertical dimension is always stretched to make the important 3D features visible. That’s basically what we are doing here, too: In order to make the point that rotating flows are largely 3D, we blow up the vertical dimension so people can actually observe that claim. Plus then there are all those cases where rotating flow actually isn’t 2D!

For which experiments might a high-walled tank (or a higher water level) be helpful?

For example the Ekman layer experiment. If you want to see the bottom boundary layer thicken over time as friction propagates upwards through the water column, you need to look at it from the side and over a certain period of time, so the water needs to be deep enough to be able to see parts of the water column that are already affected by friction, and then the upper part that isn’t and that’s still in solid body rotation.

Or if you want to observe the difference between rotating and non-rotating fluids, the extra height helps to show that rotating fluids are 2D whereas non-rotating fluids are 3D. So just to make it easier to observe that structures are really 2D, it helps to stretch the vertical axis.

For example of thermal forcing in rotating and non-rotating cases (And yes, I see the irony that i am showing a top-view of the rotating case. But observing by eye and taking pictures in which you can actually see what you saw by eye are two very different things).

Or non-rotating vs rotating turbulence (check out the movie in the linked blog post; makes it much clearer than the picture below).

Or those cases of rotating fluid dynamics where we force the flow to become 3D by mean tricks like slow rotation on a sloping bottom…

In reality, there were other reasons, too: Firstly, we couldn’t find cheap options that matched all our requirements (We wanted something that had a diameter close to the maximum that we could fit on our rotating tables, that was cylindrical, had a flat bottom, had clear walls and would be robust enough to use with students).

Secondly, I own a glass vase with a similarly high walls that we used as tank on our prototype of the rotating table. I still use it at home, but we didn’t want to go with glass for the tanks we use all the time with students & for outreach, for obvious reasons. But since we were happy with the dimensions of the vase, we just went with it. Never change a running system, right?

And a practical reason: Emptying a high-walled tank by carrying it to a sink and throwing out the water there is much less likely to make a mess than emptying a lower-walled tank with the same water height in it. Waves created by moving the tank is all I am saying…

And also I think observing vertical structures develop in fluids is always fun! :-)

#DryTheory2JuicyReality featured in our university’s newspaper!

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We’ve had a busy couple of weeks at #DryTheory2JuicyReality with our new rotating table, our seminar presentation last week, attending BOOT in Düsseldorf, and more, all in the name of science communication.

Super nice to see our efforts recognized in print: Our project was featured in the university newspaper! Read about us here in German and in English!

Click to read the article on the university’s website

#WaveWatchingWednesday

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Another summary post of my wave watching Insta @fascinocean_kiel! Enjoy!

What is going on in the picture below? Just from looking at the picture I could only guess, but luckily I took dozens of pictures of that location with slightly different angles and at different times, so I could figure it out!

To the right of this picture, there is a groyne. Some of the higher waves, like the one whose crest is perpendicular to the beach (looking like it’s wiping out all the smaller waves) make it over that groyne. Most don’t, so they get bent around the groyne and approach the beach with crests more or less parallel to the beach, like we would generally expect waves to behave. And there you have it: a really weird-looking wave field!

It’s so fascinating to observe water interact with obstacles, not only because of what waves are created (although that’s definitely awesome!) but also because of what water does to things that try to stop it.

Take for example groynes, those structures that are built into the sea perpendicularly to the beach. Their purpose is to regulate beach erosion by breaking up the current along the shore and creating pockets of calmer water where sand falls out and accumulates on the beach rather than being taken downstream with a current. There are many different kinds of groynes for different purposes. Those that always stick out of the water or those that are submerged, those that are completely closed off and those that let a little water and sediment through. And I find it so interesting to look at structures and ponder why specific design choices were made.

In this picture, the groyne is old and either eroded or was designed for a coastal shape that has changed since: high waves manage to flow around the landward end of the groyne, eroding the beach there. Looks cool, but not so cool for coastal protection…

But it makes it even more interesting to come back to that beach soon to see how things develop: very close by old groynes were being pulled out of the sand as we walked past, so there will very likely new coastal protection measures in place next time I visit! What do you think what they will look like?

Next, I went to the trade fair “BOOT” in Düsseldorf for a long weekend. Super exciting! Here are my posts from that huuuuge trade fair on water sports:

#WaveWatching of a different kind these days thanks to @deutschemeeresstiftung and #loveyourocean: #TheWave at #BootDüsseldorf2020. I have to make time to talk to one of their technicians who are surely around… (Edit: In the end I didn’t manage to track one down. I saw where they were sitting, but there were too many layers of security between them and me…)

Then: hotel breakfast #WaveWatching.
Here is how you do it: take a latte glass (the glass, not a glass of latte. That would obviously work, too, but I have posted about that soo often by now that it isn’t as exciting any more ;-)), two coffee crema and then pour a little milk in. Voila: diffusive layers form! That’s a really nice example of double-diffusive mixing where heat and milk diffuse at different rates. And if you disturb the stratification, for example by moving the glas, you get internal waves!

Fascinating how different people have such different perspectives on water.
Mine today was one I am not very familiar with: mainly through microscopes, trying to adjust them in such a way that visitors at the #loveyourocean booth of @deutschemeeresstiftung could get a good look at plankton. This would then lead the conversation to food webs, microplastics, and more. Very different from my usual topics, but definitely fun!
Also: taking pictures with your phone through a microscope is a lot more difficult than you would imagine!

(Yes, I know there are microscopes that take proper pictures…. But where is the fun in that?!)

Pretty impressed by the effort people at #bootdusseldorf2020 put into creating fun environments to try different water sports. Indoor pools with wind machines, live grass and bushes and stuff! And also impressive how different the moods are in different areas of the congress center. Pity it’s already over for me!

Also super awesome: the THW‘s rescue divers. And how air bubbles rapidly increase in volume as they rise to the surface :D

For this month’s #SciCommChall, I show you the contents of my trusty handbag. You see it in the picture here and in my profile picture. Wherever I go, it goes. And there are surprisingly many things in there that I carry with me for my #SciComm! Check out the blogpost!

Not really wave watching, but close enough: the light installation on this church’s steeple shows how low the cloud cover was two nights ago. Looks very cool, me thinks! Even cooler than on clear nights where you don’t get the projection on the clouds and the light just disappears into space (or wherever)

Yay! A little #WaveWatching on my way to a meeting in Berlin. Can you see which direction the waves are coming from? Check out how the ring waves are traveling from the buoy!

On a work trip, combining scouting locations of interest in terms of #biodiversity with (surprise!) #wavewatching. Luckily the duckies were cooperating and making interesting waves in their feeding frenzy. I especially love the splashing as the jump up and down the stone edge of the pond!

I think these ducks are so pretty! Remind me of a tiny figurine I owned as a child and that — I remember that vividly — had a glued-on part where something had broken off when it fell down…

And that’s it for this week’s #WaveWatchingWednesday! See you next Wednesday! :-)

What’s in Mirjam’s bag? #SciCommChall

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My friend Nena has taken over #SciCommChall and gives us super fun monthly challenges to practice our scicomm muscles and try out new things. I love a good challenge, and for me this is really a great way to expand my scicomm portfolio and skills. Check it out!

This month, she’s given us the “what’s in your bag?” challenge. I am excited! Some of my stuff might actually be specific to my #wavewatching and #kitchenoceanography obsessions (even in the tiny handbag I am wearing in the picture below!).

Or they might not be, you tell me: What’s in YOUR bag and why? What’s specific to the science you are excited about?

In any case, here we go with mine:

  1. This is my absolute favourite handbag of all times! It’s always stuffed, but I love it! I carry this on me wherever I go, and my work bag comes in addition to this (give me a shout if you would want to see that one, too). All the stuff around it in the picture usually lives inside
  2. Not so surprising: A little card holder with all the cards I need to carry
  3. And a little coin pouch
  4. Emergency tea. Can’t get caught anywhere without some. Clearly have to restock, this is my least favourite of the favourites I usually carry with me. Also great as dye tracer in a pickle
  5. A spork. Because no single-use plastic! Also for stirring, measuring, that kind of stuff in experiments (we use food dyes, no worries…)
  6. I carry some minerals to prevent (or quickly counteract) cramps. No oceanography connection there
  7. Seem to have skipped no 7 on the picture! Probably to make up for something not pictured, because I was working with it when I decided to accept this challenge and it therefore wasn’t in my handbag: My (tiny) bullet journal. But it’s actually in the picture above, so that’s proof that I really always carry it with me!
  8. Pens! Several. One waterproof, because #kitchenoceanography. Where is my pencil? Seems to have gotten lost
  9. Sticky notes! Always need them
  10. My battery bank for my phone, because my phone holds my life. And I need it to take pictures and movies, to write notes, to do Social Media with it or blog on it. The battery bank is heavy, but for me totally worth always carrying it with me
  11. Headphones, charging cables for my phone & battery bank, that kinda stuff
  12. Oh, now it’s getting interesting! A selfie stick and a microphone for my phone to do wave watching selfie videos with, after I realized how horrible the sound quality was when I was on a Swedish research ship a couple of months ago
  13. A fabric bag because I always end up having to carry stuff somewhere and, as you see, the handbag is tiny
  14. Ziploc bags. Because you always find cool stuff at the beach… At least I do :-)
  15. Emergency cash and emergency plasters
  16. The pouch where the plasters are supposed to be, together with some emergency stuff against headaches, a tiny pocket knife (which I use SO MUCH! Hello, unboxing new rotating table & tanks!) and the very much undervalued lip balm. Which has saved tank experiments several tanks when something was leaking, everybody was freaking out, and I was just like “let me get my lip balm from my hand bag…”
  17. Paint swatches that I got when my nieces and I went to the crafts store because we had the deal that everybody could get three and only three, and I decided that “everybody” should include me ;-) Also I love the colors.
  18. A small scarf and wooly hat, because wave watching happens outside and I like my throat and ears to be warm
  19. A measuring tape. Because knitting, and then I forgot it was there. Came in really useful when we were unboxing our new rotating table and tanks and were cataloguing the inserts and stuff — measured everything right away to know what we are dealing with!

And what’s in your bag?

A recent seminar presentation on “one should really play more!” and our rotating tanks

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Using “One should really play more!” as title of a presentation in a serious scientific colloquium might seem like a bold move, but the gamble payed off: a large, interested audience including everyone from students to professors enthusiastically dropped ice cubes and food dye in our LEGO-driven rotating tanks and passionately discussed their observations when on Monday, Torge and I gave a presentation in the “Ocean Circulation and Climate Dynamics” colloquium at GEOMAR. After briefly presenting the context of our PerLe-funded “Dry Theory to Juicy Reality” project, we invited everybody to play, no wait … conduct experiments with four of our rotating tanks that we had set up. Nils, Ludwig, Jakob and Hendrik from our current atmosphere and ocean dynamics class were there to help out at each of the tanks to make sure that people actually dared to touch the equipment but also make sure that they would see something meaningful in each experiment, while David took amazing pictures (which you see over on our new teaching ocean sciences blog, these are all mine).

It was such a pleasure to see everybody — from students to retired professors — drop ice cubes and drip dye, falling to their knees to have a better angle to look at tanks, and enthusiastically discussing observations and theory. Even though I am convinced that everybody should really play more, it felt really good to see people enjoying it, and not only for the aspect of play, but also for the scientific discussions that are inevitably provoked when you look at tanks.

Also it was great to be back in that auditorium 10 years after having defended my PhD there. So many things have changed, yet so much remained the same!

#WaveWatchingWednesday

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For #WaveWatchingWednesday: A collection of pictures that I took (and shared on my wave watching Insta @fascinocean_kiel over the last week. For some reason with a lot more commentary on here than on Insta itself, don’t know why. Maybe because I am writing this while it’s still dark outside and I am waiting for it to get light so I can go do some wave watching? ;-)

Nothing makes me instantly as happy as looking at water. Especially blue water, but any water will do. This picture below? That’s what happiness looks like for me. No matter what else is going on in my life, this view instantly makes me feel calm and content. And happy. What is it for you that has a similar effect on your emotions?

And I discovered a new perspective that I am a little obsessed with right now. Right where I live, there is a big art piece out of metal that looks a little ship-wreck-y and very nautical (it’s called “Hafen 77” by artist Felix Fehlmann). It has circular holes in it, reminiscent of portholes, but it never occurred to me before to use them to frame pictures in. This is my fist attempt at it — what do you think?

Now that I have discovered that porthole view, I wanted to go back the next morning to take a picture with different lighting. Unfortunately I was 2 minutes late to catch the Sweden ferry through the porthole! I hadn’t thought about how that would make a great picture until I saw her and it was already too late. But luckily there are more ships going in and out Kiel port, so there will be another chance!

To keep my Instagram feed looking nice I couldn’t post the next porthole pic right after the first one, but luckily there was pretty cool wave watching that morning, too!

This is a picture of several ducks’ wakes: see how they are forming 2D Mach cones with the ducks at the tip? Taking pictures of waves is always best around sunrise and sunset, because then the contrast between a light sky and dark land helps show the wave structures as differently sloped parts of the waves reflect different parts of the high contrast surroundings.

Here is the mystery spot again (well, mystery for Instagram, I already wrote above that this is the “Hafen 77” art by Felix Fehlmann, so you already knew).

But this time also “zoomed out” so people can figure out where this is!

And then I had a brilliant day trip with Sara!

Sylt, an island on the german North Sea coast, is amazing for wave watching. But amazing waves come at a great cost: the nice sand beaches are threatened by coastal erosion and have to be protected and maintained with huge efforts.
On our mini-excursion, we saw many different measures for coastal protection, like tetrapods (those gigantic four-legged concrete structures) and different kinds of wave breakers.
I took 625 pictures (ok, mainly of waves, but also a lot of the ongoing coastal protection construction works!) that I won’t manage to sort through tonight, so this is your chance: which coastal protection structures should I write about first? (All the following pictures belong to this blog post until the next text interrupts the flow ;-))

The next post wasn’t a wave watching post, for #SciCommSunday I wrote about why I post selfies on my social media (and this picture is clearly not a selfie, it was taken by my colleague Sebi Berens (www.sebiberensphoto.com / @sebiberensphoto)). But I like it a lot and was excited to post it on my Instagram using the excuse of #scientistswhoselfie ;-)

It’s really difficult for me not to watch the spectacle of the Oslo ferry making a U-turn in the narrow Kiel fjord before backing up into its berth. So difficult, that I took my conference call to the roof terrace and my colleague asked if I was swimming in the sea because apparently that’s what it sounded like on the other end. So ferry-watching was unfortunately cut short.

But watching the ferry wasn’t my main reason for visiting Geomar, see below what we were up to: Torge and I presented a seminar on “It’s always a great idea to play! Teaching ocean and atmosphere dynamics with rotating tanks” (or similar, can’t remember exactly ;-)) We gave a short presentation and then invited everybody “to play”. We had four rotating tables set up, each prepared for a different experiment. And people seemed to enjoy doing hands-on experiments a lot. So hopefully there is a lot more playing with a lot more players in our future! :-)

And then a little more about that amazing day trip to Sylt:

Why is there so much foam on the beach? Two factors are playing together here: Breaking waves trapping air under water that tries to get back up and out, and dissolved organic matter lowering the water‘s surface tension. Both have to be present at the same time: if the water was calm and no waves were breaking, there wouldn’t be a way to get air into the bubbles of the foam because no air would get underneath the water. And if the surface tension wasn’t lowered, the bubbles wouldn’t be able to exist, they would just collaps into drops of water.
Pretty counterintuitive that one has to lower surface tension to make bubbles that are stable, isn’t it?

(Next four pics show different foam situations on the beach)