Tag Archives: wave watching

Feathery wake approaching! #WaveWatching in Kiel Holtenau

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A week ago already, Frauke and I went on an evening walk in Kiel Holtenau. Beautiful wave watching to be done there as always! Here you see the one side of a ship’s V-shaped wake approaching our vantage point. You can see the individual “feathers” of the wake: Short wave crests, all parallel to each other, but slightly shifted to the side to form a straight line (well, two straight lines to form a V with the ship at its tip, but the other side of the V is not visible on this picture).

And this is what it looks like when the wake has moved past us: Looking on the back of the feathery shapes. The ship that made all these waves has long sailed away.

On #WorldOceansDay, revisiting one of my favourite places to wave-watch: a broken wave power plant

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Anyone who has ever read my blog, seen my Instagram, or met me in person knows: The ocean is hugely important for me. The ocean is important for my mental health, looking at water just makes me happy and calm and content. The ocean is also the foundation of life on this planet: It supplies more than half the oxygen we breathe, it moderates temperatures such that I am happy to go swimming in Kiel fjord all year round (ok, that’s also because I am slightly insane), it provides us with food, work, goods.

Today, on World Oceans Day, let’s celebrate the ocean by looking at one specific aspect in which it is amazing, and that is in how much energy it contains. In heat that is stored in it. In dissolved salts. In its movement. You know I am addicted to wave watching, but there is so much more you can do with waves than just watch them, even though that’s not as easy at it seems.

One of my favourite wave watching spots is a broken prototype of a wave power plant close to my friend Elin’s cabin on an island off Bergen. The location was chosen for the enormous wave power that slams up on the coast here most days, and that’s also why the prototype unfortunately didn’t last very long.

In the movie below you see the spot where a turbine used to sit which would be powered by water pressing air up by being funneled into a sub-sea reservoir, and then sucking air back out when the wave retreats. And you see how, by the way the funnel is built, the not-so-enormous waves outside get translated into quite a change inside that hole. Wait for the splash! Can you imagine the movement of the air column above, where the turbine used to sit?

We weren’t even there on a particularly wavy day, so imagine the powers at work here on days with a lot of waves! The forces at work here are enormous. And just because we haven’t figured out yet how to make wave power work well in the ocean’s harsh environment, that doesn’t mean that it isn’t figureoutable!

Picture by Elsa du Plessis, used with permission

Even looking at these pictures and the movie I feel the effect the ocean has to me — giving me a sense of calm purpose and inspiration. Enjoy your World Ocean Day, and make sure to appreciate some water somewhere today! :-)

Wave watching in an end moraine lake in Brodowin

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On our work trip to Brodowin to prepare the GEO-Tag der Natur (which will take place here only  a little more than a week from now! Crazy!), I had the chance to do some cool wave watching on different lakes.

Above, for example, you see wind waves coming in from the right, and their very distinct reflection on the left row boat.

Below, at the stern of the left row boat, you see a sudden gust of wind, causing lots of capillary waves, and thus high surface roughness.

And below, what would you guess is the secret to the ring waves radiating away from the end of the pier? It’s a surf board, bobbing up and down in the incoming wind waves!

I just love looking at water, it has such a calming effect on me, even in 35 degrees heat (which I am really not good with).

I love to see how the more lively wave field offshore gets calmed down as only longer wave lengths make it through the water lily frequency filter! And how the wave crests get bend as they reach the shallow shore.

Now, different lake. This one is 38 m deep! Would you have guessed that?

Here you see that we are standing on the downwind side of the lake: Smooth water on the other edge in the lee of the land, then, after sufficiently large fetch, waves that grow more and more the further they have progressed over the lake.

Same lake, same phenomenon, different view.

And the last bit of the lake just to give you an impression of the glacial landscape it is situated in, explaining the very steep slopes and the 38 m depth.

This would be such a lovely place to sit at and enjoy the view, if only there was a little shade…

I find it fascinating how the shape of the waves doesn’t change as they approach the shore. That’s because the shore is so steep that when, at last, the waves start feeling the bottom, they have already reached the edge of the lake and didn’t have time to change their shape.

Same phenomenon, different view.

Water is just so amazing :-)

Observing a breeze making waves on Parsteiner See

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Yesterday, I happened to be at Parsteiner See for work.

At first, the sea was completely calm and the only waves were the ones we made doing our photo shoots, like so:

Other than that, the lake was completely calm.

But then suddenly, I spotted a breeze going over the lake. It becomes visible in the dark areas with higher surface roughness, where capillary waves have formed.

As the wind keeps blowing over the capillary wave area, those waves grow and then at some point become “regular” gravity waves, that travel out of the region where they are directly forced by the wind. See below: In the background you still see the area with higher surface roughness, whereas in the foreground gravity waves are coming towards the shore.

As the wind keeps blowing over the surface, forming capillary waves over larger and larger areas, those areas all show up as darker and rougher.

And the cute little waves keep coming to the shore :-)

Wave watching in front of the Reichstag. That’s my kind of sightseeing!

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Did you notice that most tourist ships on the Spree in Berlin don’t actually have nice bow waves? Luckily I found one that does! (see above)

Because what then happens is that a nice wake develops, too. Below you see the turbulent wake right behind the ship, and the feathery V-shaped wake (with the ship at its tip) spreading out.

And what’s really cool is how that V-shaped wake gets reflected from the sides of the Spree, coming back towards the middle. Can you see the two wave fields?

And once they meet in the middle, you get a really cool checkerboard-like interference pattern!

And yes, that’s the German Parliament in the background…

Below, you see the wake of a coot (apparently, according to my dictionary. I will call it duck for now…).

And now the duck’s wake and a ship’s bow wave!

Do you make everything you see about your favourite topic, too? Then check out this month’s #scicommchall!

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?

Wind-driven waves in natural flumes for #flumefriday

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On a bike tour with my friend Frauke in Greetsiel two or three weeks ago, she pointed out how well one could see that the waves on the puddles left in the Wadden Sea close to low tide were wind-generated. That was that for the bike tour — now I had to take pictures.

Below you nicely see the ripples that are created where there are longer stretches of puddle aligned with the wind direction, i.e. where there is enough fetch. And you see how the waves get diffracted behind topography, fanning out downwind of slits! The wind is coming from the right here, almost in the direction pointed out by the looks-like-an-arrow-but-is-plastic marine litter.

Here we are looking in the opposite direction, the wind now going left-to-right. Do you see the one slit in the lower half of the picture and how wave crests propagate almost perpendicularly to the wind direction, just because there are waves going through that slit? Pretty cool, me thinks!

The really shallow water with all the stones in it made it really easy to look at waves from different directions. Below, we are looking downwind, at the back of the waves.

And below we are looking upwind. See how different things look now? You still see the wind pushing the waves, the front slope of the wave is a lot steeper than the back slope.

I love the picture above, makes me want to put my hand in the water and play with the waves :-)

Some port of Kiel #wavewatching: A feathery wake getting fanned out and bunched together!

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Wakes are always interesting to watch. But usually, I am showing wakes of ships going straight ahead. So today, I have something cool for you: The wake of a ship doing a 90 degree turn!

And what that does is that the feathery wake that is usually V-shaped now gets deformed!

And this deformation of the wake means that on one side of the wake, the feathery waves that are usually parallel now become fanned open, while on the other side they get bunched together. See?

After the ship had gone a lot further, there were still effects of its wake visible, both of the waves created as well as the turbulent wake that is still visible in a surface roughness that is different from the rest of Kiel fjord, and a little foam.

Fascinating how long such a wake stays visible!

And fascinating that such a small boat — even though it was going a lot faster — does create waves that are a lot higher than the much larger ColorLine does!

If you look at the large ColorLine, you see that there is a large turbulent wake, but (at this speed) hardly any waves created, so hardly a V-shaped wake!

Of course, it speeds up a lot as it sails out of Kiel fjord, and then things get more interesting wave-wise here, too :-)

Sunday #wavewatching. Shallow water waves, deep water waves, #wakewatching, reflections, refractions, and more.

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This is the blogpost I wanted to write today before I got distracted by all the adventures on MS Stadt Kiel with sightseeing and swing dancing and all the good stuff that wasn’t wave watching. I had even uploaded all the pictures of this morning’s wave watching walk on my blog already, but then things just got too exciting… But here we go now!

Here we see a really nice example of shallow water waves: The wavelength is a lot longer than the water depth and the shape of the waves looks very different from the almost sinusoidal waves in deep water: The troughs are very long and the crests short and steep.

And here they show the influence of water depth on phase velocity: Where the water gets shallower and eventually the land falls dry, the waves get slowed down. This means the part of the wave crest that is still in deeper water is faster, overtaking the shallower part, and thus the waves get bent around, towards the shallower areas in the water.

For comparison here the shape of waves in deeper water. Do you see how they are much more sinus-shaped?

Above we also see fairly well how gusts of wind change the water’s surface roughness: where the water surface looks darker, it is covered in small capillary waves caused by gusts of wind.

Btw, if you were wondering where the longer wave length waves came from: They are the wake of a boat accompanying the training session of some race kayakers.

When those waves hit the sea wall, we see nice reflections and a checkerboard pattern!

Btw, I find it super eye opening how the structures that, to me, absolutely dominate the picture above are not picked up as dominant in my comic app (see below). Of course the structures of the power plant or sea wall are more prominent, but the criss cross of the reflected waves is hardly visible. Maybe that’s how little it is visible to most people even in the photos? On my Instagram poll on whether comic-y-fying pictures helps to show what I am talking about, 60% of the responses were that yes, comics make it easier to see what I mean. Not quite sure yet what I will do with that information moving forward…

Something else really curious today, btw: The way the sea floor looked! Usually there are lots of ripples here, mostly parallel to the sea wall. And today these weird patterns of darker (finer?) sediment. I think I need to observe the sea floor more consciously to figure out what’s going on there!

And now the race kayak and accompanying boat are coming back. I love how you see their wake and then that bird’s wake in the picture below!

And then, finally, some larger waves, again the wake of some ship that I didn’t pay attention to.

And sometimes, the reflections are just suuuuuper difficult to see when you don’t know what you are looking for. Do you see them in the picture below?

Gravity waves and capillary waves on Kiel fjord

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Yesterday, I took some pretty pictures of a red balloon floating on Kiel fjord, some seagulls swimming close to it, and — of course, most importantly — the seagull’s waves. You see some that they just made where you can still see how they relate to where they are swimming now. But then there are also these large circles from previous movement, and the origin of those we can only guess. As we see from the seagulls’ wakes, they haven’t been swimming in that direction long, and they started out from a resting position. Maybe the large circles are from when they landed? We can only speculate.

I’m showing you the pictures of the seagulls and the ballon because I think they are pretty, but also to have a reference for what “normal” waves look like. “Normal” meaning that they are waves whose restoring force is gravity.

There is, of course, other kinds of waves.

Check out the picture below. It’s super choppy, but do you see parts that look different? It’s an overall choppy day, so it might be a little difficult to see what I am talking about.

Let’s zoom in to see some capillary wave action! Capillary waves are the ones that are restored by surface tension rather than gravity. They are a lot shorter than “normal” waves, wavelengths are only up to less than 2 cm long! And they often appear as several wave crests right behind each other, like below. Short wavelengths travel faster than longer ones, which is why from a main crest, more and more capillary waves emerge which seem to be bunched up moving right in front of the main crest. Pretty cool, I think!

Edit, a couple of minutes after initial publishing this blog post:

I saw a friend use a comic app on Instagram and, of course, went down that rabbit hole. So here is a recap of the pictures as the app sees them below. Do you feel like the waves are easier to see in the comics than in the pictures?

Below, you see the seagulls as they have just started paddling forward, and the large circles are still fairly close to where the seagulls are.

Now the seagulls have swum a little further, but you still see where they initially started out. And you see that the time lag between the two pictures really isn’t that large — the large wave ring hasn’t propagated a lot compared to the balloon (which is also freely drifting, so maybe that’s not the smartest comparison).

But my capillary waves become a little clearer now, I feel: The bunches of parallel wave crests on the right half of the picture that are now drawn in black (while all the choppy stuff is just shared, but not contoured).

What do you think? Are these pictures helping to show what exactly I am talking about, or is it just as confusing as before, only in a different way?