Tag Archives: fetch

Wave watching in Kleinwaabs — and my first real Insta story!

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So today (and tomorrow and the day after) is the big event that I have been working towards all year in my not-so-new-anymore job: The GEO-Tag der Natur! If you are curious about what’s going on there, check out our Instagram account @geo.tag.der.natur that Kati is doing an amazing job with!

As you can imagine, the weeks running up to this weekend were quite busy and a little stressful, too. So last Sunday I went to the beach to hang out with friends and do some wave watching! Because nothing has a more calming effect on me than watching water…

For example below we see nicely the effect of the wave (and wind) breakers on the wave field. In the lee of the wave breaker, the water is completely calm, whereas towards the right of the bay waves form and grow larger and larger.

And below we see a pretty cool “diffraction at slit” example: Straight wave fronts reach the slit between two wave breakers, and as they propagate through the slit, they become half circles.

But to relax and get my thoughts away from my job, I tried something new: I created and posted my first ever Instagram story! I’m not quite sure it’s my format, but I definitely had fun! What do you think? Would you like to see more of those? (I only just realized the story is in german and my blog in English. Posting anyway… Would anyone like to see this kind of stuff in English? Then please let me know and I’ll see what I can do…)

https://vimeo.com/341862851

(P.S.: Since I made this for Instagram, the format of the video was optimized for viewing on a mobile phone. Therefore it looks crap embedded in a blog. But some you win, some you loose…)

What do you do to relax and get your mind off of work? Wave watching and posting about it on social media? Have you ever tried that? Or what else would you recommend?

Atmospheric & water wave watching

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What I find really fascinating about watching waves in the atmosphere rather than on water is that all the waves that become visible are not surface waves like on water, but internal waves. Which we have to go to great lengths to make visible in water (for example by adding dyes in tank experiments) but which we can’t just visually observe in the sea in the same way as we can in a transparent atmosphere.

In the atmosphere, however, we also don’t see every internal wave going on, either, we need very specific conditions for them to become visible. So whenever I see one, I start pondering why we see exactly what we see, why there are clouds in some places and not in others. Below, for example, we see the troughs of an internal waves in cloud stripes, but the crests don’t form clouds. Fascinating how just displacing air by a little bit can cause clouds to form and to disappear!

And things become super cool when you combine atmospheric wave watching with “normal” wave watching like in the picture above. There you see the rough surface with tiny little wind waves in the background, waves coming around the break water, the calm water in the lee of the break water, sheltered from the wind, and then the reflection of the atmospheric waves on the water.

And you thought it couldn’t get any better? Well, you were wrong! Now there are also some waves on the water, plus soap bubbles! :-)

Now, for a thought experiment: What would soap do to the waves? Would destroying surface tension actually matter? I think not in this case, or t least not close to land in the picture above, since the waves are mainly gravity waves, not capillary waves. But what do you think?

Influence of wind and water depth on a wave field (or: a beach vacation in Dornumersiel)

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I took the selfie above mainly to send to my mom from my vacation in Dornumersiel on the German North Sea coast. But then when looking through the hundreds of pictures I took that day, I realized that not only was my hair parted on the wrong side because it was so windy (ha!), the wave fields to my right and left looked actually quite different, without the reason for that being immediately obvious. So let me show you a picture facing the other way.

Above, you see this wave breaker like structure, protruding into the sea. The wind is coming from the right side, thus the waves are a lot larger on the right side of the breaker where they are getting more and more energy from the wind as they come towards us, than the waves on the left, the lee side of the breaker, where they don’t get any new energy input and are just refracted around the breaker.

Looking the other way, towards the shore, the difference becomes even more clear (picture below) isn’t this fascinating?

I really like watching how waves interact with structures. Below, for example, we see that the wave crests are coming towards the wave breaker at an angle, and that they are reflected and traveling away from it, too. This contributes to making this side look a lot more choppy than the other side!

On the other side, the waves look smooth. I was still standing on the breaker when taking the picture below, and you see where the sea surface is still sheltered from the wind and where the fetch is long enough so the surface roughness increases and ripples and capillary waves form.

Since we are in the Wadden Sea, the shore has a very shallow slope going into the North Sea, so waves look super interesting when they are in the shallow water. Below you see many many almost-breaking wave crests behind each other, coming towards us. The water depth is clearly a lot less than a wave length, the waves are interacting with the bottom and thus have really long and uniform troughs and steep, short crests. (btw, for those of you wondering how I could say anything about water depth in my #friendlywaves post on Saturday: This is how. This is an example of waves in very shallow water, and you clearly see their shape being different, don’t you?).

I love looking at the details of where they hit the beach! All the sparkle, all the little Mach cones around the pebbles where the water is running off, all the small capillary waves!

Below, someone accidentally walked into my picture, but that’s actually a good thing, because it gives you a scale, and if you look at the little wave rings that were created when she put her foot into the water and it splashing forward a little. The wave rings actually have comparable sizes to all the other small stuff going on on the sea surface!

And what’s also pretty impressive: How the crests get refracted by changing water depth. Below it almost looks like parabolic shapes coming in from the right, right? The side of the parabola that is further away is actually the wave crest that is coming in from the open sea, and the rest, i.e. the actual curved part, is partly diffraction around the breaker and then refraction because of changing water depths. So cool!

Since I spent quite some time there, here is a picture later that day with a lot less water. Tides and all that… ;-)

And then another day with a different wind direction and less sun.

I think it looks really cool to see the fairly wide area to the right of the breaker, in its lee, where the surface is really smooth!

So far, so good. Gotta go now! Do you find this as fascinating as I do?

Interesting pilot ship #wavewatching at Kiel canal

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Some throwback Friday evening wave watching (at the locks at Kiel Holtenau with my friend Sara for a nice and relaxing end of the week) to start the new week. The best!

First: The pilot boat going towards the locks. Unusually visible wake — they are going fast today! Plus an interesting sheltering of waves: The wind is coming towards us so outside of those floating pontoons are a lot larger than the ones on this side that haven’t had enough fetch to build up.

Below we see the same wake: But do you see how it’s just ending on the left? That’s because the pilot boat went in behind the jetty on the far side of the fjord, and it’s only these bits of the wake that were able to propagate outside before the boat went in and the waves don’t make it out of the small channel created by the jetty.

And below the pilot boat going out again in a curve: Love how you see the turbulent wake as well as the deformed V-shaped feathery wake. When you look from the pilot boat down on the picture, do you see the individual “feathers” of the V? Love this perspective on wakes!

And this is what you will see of me when you meet me for a coffee anywhere near water. Sorry Sara, but thanks for the picture! :-)

Same wind, different waves, or: the influence of fetch length on the size of waves

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I just found this picture that I took back in May near my friend Elin’s cabin on an island in western Norway, and it’s a really nice illustration of how the same wind will cause very different waves depending on whether it’s blowing over the sea for many kilometres, or over a puddle for only a couple of centimetres.

Expedition learning

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In July I will be involved in teaching an “expedition learning” course for a week. It will be all about coastal protection in the Kiel region, so two colleagues and I went on a private expedition to scout out what can be explored where. This is a very picture-heavy post, be warned! It’s more a note-to-self to document the different beaches we looked at than something I expect anyone else to be interested in.

We started out in Friedrichsort, where there were nice breaking waves to be observed. My part of the course, you might have guessed it, will be on observing waves…

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In Friedrichsort there is a lighthouse on a small headland, and there are sand banks around it that make for very interesting wave fields, like for example below, where the sand bank almost seems to filter out some wavelengths.

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Looking seaward over the sandbank, we see breaking waves over the shallow part, and waves being bent around the sand bank.

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A similar thing could be seen on a tiny headland: Can you see how one and the same wave crest gets wrapped around the headland?

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See? So cool!

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Btw, you might have noticed the weather changing a lot over the last couple of pictures. It’s April, I guess… But a couple of raindrops here and there make nice tracers for the time since the last wave washing up over the beach ;-)

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Always fascinating: When you can see wave-less spots that are shielded from the wind, and then local wind waves and others that are travelling in from further away. And breaking on a sand bank…

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Also, did you see how nice the weather was for a couple of minutes every now and then? ;-)

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And here is a close-up of the waves breaking on the sand bank.

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Oh, and looking back to where we came from: That’s the lighthouse on it’s headland right there! And my two colleagues figuring out what’s wrong with the GPS they brought. Their part of the course will focus on more geological things than mine…

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But I really like this view!

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See how nice and regular the waves are that reach the beach even though the local wind field is really messy (as you see a little further offshore) and the waves have gone over the sandbank?

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Oh, and always one of my favourites: When nice and regular waves hit a stone and it sends off wave rings. Love it!

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One more, because it’s so nice!

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And here waves bending around a wave breaker thingy.

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And this is a picture that really nicely shows how if you don’t have wind, you don’t have waves. The lagoon there is sheltered so well that you can actually see the reflection of the bird sitting on the edge!

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And here we have a very nice superposition of waves coming from different directions and with different wavelengths.

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And waves coming through the “slit” between sandbanks and spreading as segments of a circle. Nice!

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Oh, and more waves breaking on the sand bank.

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After a while, we reached Falckenstein:

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Not so far away from where we started out at that lighthouse over there:

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Another interesting superposition of wave fields.

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Oh, did I mention we did a lot of walking in the sand? About 20k steps. Well, I guess that isn’t even too bad…

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Below I really liked the criss-crossing of waves. It’s actually one wave crest crossing itself after being bend by the shallowing water.

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And those waves get deformed a lot, too!

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And here we knew that it was a matter of minutes until those rain showers would be where we were…

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Luckily, this shower went over quickly, too.

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And this is the kind of stuff the other courses will be dealing with: Awesome formations in the coast!

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Ha, another weather front:

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And this is my favourite geological feature: there are interesting features in the sand/soil/stone (however you call it?) and then erosion marks, clearly made by water, right below!

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A little bit further along the coast, there are weird wave breakers and if the wind hadn’t died down, we would probably have been able to see more interesting waves than these…

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But the waves below were really cool: There were the ones that you clearly see on the picture at an angle to the coast, and then there were waves that came in perpendicular to the coast (so the wave crests were parallel to the coast) and they washed the other waves on the beach and back into the sea. I should really upload the movie…

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So those waves above caused ripples in the sand which are parallel to the water line, even though in the pictures the other wave field is a lot more visible!

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See?

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We ended up in Schilksee and had a look around the marina. Apart from the typical wind / no wind resulting in waves / no waves, we saw……

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…this! Pretty cool, huh?

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And again:

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One last look at the coast near Bülk.

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At this point, only one of us still felt like exploring every nook and cranny…

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Even though there were some pretty nice wave fields, but we could see them from our vantage point without doing an extra step ;-)

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Actually, there were a couple of cool features on the beach still. What’s up with those little bays?!

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We ended the day with trying this very cool contraption to measure the coast with. It was actually a lot of fun!

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And you wouldn’t believe how much work it was to hold that ruler thingy in the wind!

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So yeah, that’s what we did. And how was your day in the office? :-)

Wind waves

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No matter how often I’ve seen it, I still find it absolutely fascinating how the tiniest structures can have a really visible effect on the downwind wave field. Like for example that pier below, leading to the little hut at the end. There is probably a meter and a half between the water surface and the gangway, which is propped up on really thin pylons. Yet, you clearly see that there are visibly fewer waves downwind of the structure. And the hut itself shades a huge area from wind.

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This kind of stuff is so cool to watch! :-)

Another wave hunt expedition: Learning to discover ocean physics wherever you go

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One of my favourite topics right now: Learning to “see” ocean physics wherever you go. For example here: A visit to my goddaughter in Schleswig, and this time we are practicing all she and her mom read about in MY BOOK (and if you have good ideas for a title for that book, please let me know!). So today I’m showing you pictures of phenomena similar to those in my book, but discovered on this recent visit.

For example diffraction when waves pass this pier:

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In the image below, I’m showing what I mean: Waves coming in from the right have straight crests (red). As they pass the pier, they get diffracted and bent around (green).

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In this spot, this phenomenon can be seen on most days. I wrote about it before, but I have more pictures from previous visits, where the same thing happens in the opposite direction, too: Waves propagating in from the left and being bent around the pier to the right.

Or we can see other wave crests, meeting a rock that breaks the water’s surface.

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Those waves (shown in red in the image below) get reflected from the rock, and circular waves radiate away from the rock (green).

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A similar thing can also be observed from a flag moored out in the water:

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This time, incoming waves are green and the circular waves radiating off the flag are red.

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And we also got to see awesome criss-crossing again, albeit in a different spot:

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Here we have the red wave crests coming in, and the green reflections.

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If we look at it from a little more distance, we can also see another phenomenon: The wave crests are refracted towards the shallower shore:

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Again the red crests are the original, incoming ones, and the green ones are the reflection:

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And then finally, let’s look at duckies again. And on waves being created by wind:

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Below you see the direction of the wind (white): One side of this little channel is shaded from the wind, so hardly any ripples there. But then on the other side, we clearly see ripples and small waves. And we see the wake the ducky made!

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And one last picture: Which direction does this little channel flow in?

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Yep. From the left to the right!

If you enjoy discovering this kind of stuff on your walks, or know someone who enjoys it, or want someone to learn to enjoy it, you might want to consider checking out my book. In my book, I show many pictures like those above, but I actually explain what is shown in the pictures rather than assuming (like I do on this blog) that my readers are oceanographers anyway… :-)