Even though I haven’t done a #WaveWatchingWednesday in a looong time, there has of course been a lot of wave watching going on. But the longer I wait with copying all the Instagram posts into a blog post, the more work it gets, the longer I put it off. Vicious circle! But here we go today. Plenty of interesting and plenty of beautiful pics! Enjoy!
It doesn’t feel like it, but today marks the 7-year-anniversary of my first blog post on my “Adventures in Oceanography and Teaching”! To celebrate, I sent out this call to action (and please feel free to respond, no matter when you are reading this):
Below, I am sharing the pictures that people sent me plus my thoughts on them, newest on top. Pictures that reached me after August 28th 2020 will be posted in follow-up posts! (Keep them coming, I love it!)
23:58 — Kristina
21:55 — Phil (San Francisco)
21:06 — Clark (Bay of Fundy)
Clark wrote an entire thread explaining this awesome observation in the Bay of Fundy. You should totally check out the whole thread & explanations on Twitter, but I had to share this video so you can see what an exciting situation it is!
20:51 — Elin (Bergen)
18:14 — Simone (Hamburg)
15:43 — Dong
15:18 — Nena (Bodensee)
15:13 — Jeffrey (Boulder)
Wow, this video is super tricky! Please check it out — volume up!
At first, I thought that the periodicity was set by eddies shedding periodically after water had washed over the obstacle. But after about the 50th time I looked at the video, the obstacle (is it driftwood?) seemed to start moving. If it is actually moving, the periodicity makes sense: The wood is trapped in place (you see that on the far side of the river) but it can move a little. It’s bopping on the water, floating at whatever height the waterlevel is at, but at the same time acting as a dam and trapping water on its upstream side, thus influencing the waterlevel. So this is basically a recharge-discharge oscillator. Maybe. Or maybe not. Any ideas, anyone? This is really tricky!
12:38pm — Gabriela (Lüneburg)
11:49am — Gabriela (Lüneburg)
11:39am — Gabriela (Lüneburg)
11:20am — Katharina (Hamburg)
I guess I said I liked a challenge… Screenshots with comments below! And check out the sound in the movie! Volume up!
10:46am — Astrid (Hamburg)
10:38am — Sara (Klein Waabs)
10:37am — Florian (all over the world!)
9:09am — Gabriela (Lüneburg)
Honestly, what jumps at me most is my ADORABLE niece who’s saying Kaffefoto (“coffee pic”). But then there is also the puzzle of why the coffe coming out of the machine looks so much lighter than when it’s in the mug (underneath the foam)? Well, the foam is the clue here! When there are a lot of airbubbles in the coffee still, they reflect light differently (i.e. from all different directions, making it look white, rather than directional, showing either the color of the coffee or a reflection) than when the coffee has settled down and the air bubbles have gone away.
9:01am — Kristin (hiking somewhere near Bergen)
9:01am — Siddharth (Sadashivnagar)
Oh I love this! I think that what Sid doesn’t show us on the very right is a narrow connection to a second body of water, on which waves are generated by wind. (Alternatively, there might be something there at the very right just outside the frame that is making waves, such as a bird or a fountain, but I don’t think that’s the case. Birds usually don’t move this regularly for long enough to generate this wave field even before you started filming and then throughout the whole movie. Fountains usually generate concentric waves (unless there are several fountains, in which case this would be a trick question ;-))) So let’s assume that wind-generated waves from a second body of water pass through a narrow inlet onto this pond. As they pass the narrowest part, they start spreading to all directions, forming concentric waves that grow over time. Well, almost concentric, because the narrowest part isn’t a perfect point source. Therefore we don’t see diffraction at a slit, but rather at a wider opening.
8:58am — Torge (Kiel)
Not a picture, but even better: He managed to fix the problem we had been having with the co-rotating video of our rotating tank. Super excited! If I wasn’t so busy today (slightly underestimated how many pics my dear friends would send me!) I would go try it out right away!
8:51am — Sam (Manchester)
8:28am — Ronja (Nordsee)
8:13am — Elsa (Bergen)
7:26am — Kati (Schönbrunn, Wien)
7:07am — Marisa (Hamburg)
6:26am — Désirée (Möhnestausee)
6:17am — FrozenBike (Khajoo Bridge in Isfahan)
I’m posting a couple of screenshots from that video to make it easier to discuss…
6:06am — Chirine (Kiel)
A week’s worth of #WaveWatching pictures for you. Enjoy!
Starting off strong: I love living in Kiel!
Totally different vibe the next morning, looking very winter-y somehow.
And then another early morning on my way to the beach. Below you see the locks on Kiel canal from the bridge that crosses the channel. I really love this view but I have to admit — if the ferry ran this early in the morning already, I’d totally take it to cross the channel rather than cycling that bridge!
But arriving at the beach always makes it worth it!
Taking the ferry back home… Love this picture! A turbulent wake, a feathery wake, those clouds… What more could anyone want?
….and we are back on the next day! Waves breaking pretty much right on the beach because the beach profile has a step shape right at the water line. Looks surreal to have those long smooth waves, than a tiny bit of breaking, then nothing but sand…
All those bubbles in the white water of the breaking waves!
I actually took the picture below because of the birds’ wakes in the center. Weird how it turned out!
And here is one just because it’s pretty!
Always surprising how many fossils there are on the beach, even though this is the 5th day in 8 days of me collecting on the really short stretch from there to the lighthouse! How many more are hiding underneath our feet and we’ll never know?
Took a very similar picture as on the day before, but I love all the different parts of the wake, the clouds, the reflections. So beautiful and calming.
Running, seal watching, swimming in Kiel fjord, now my well-deserved coffee. Have a nice Sunday everybody!
On Monday, a colleague from GEO visited me to do an interview on wave watching. Amazing day!
Taking the ferry & admiring the wakes. Isn’t it fascinating for how long turbulence persists & wipes out any waves / prevents formation of new waves? Love the different surface textures!
Also fascinating how differently wakes look depending on weather conditions!
Love how dramatic this looks!
…and how turbulent patches are so smooth and reflect the building so well. And then a sharp boundary and we are back to the normal surface roughness of wind waves!
I can’t get over how fascinating this is!
Also love the pictures for their beauty. Below: After we had arrived at a stop, the ferry has just started sailing again (see where the wake changes between smooth and turbulent and then those large eddies of the propeller rotating for propulsion?)
Very nice pattern in the waves this morning, showing constructive interference (where the crests are high and the troughs are low) and destructive interference in between where the surface is completely flat. So fun to watch!
And that’s it! Hope you enjoyed and hope it inspires you to do some wave watching yourself! :-)
More beautiful #WaveWatching pictures! Enjoy … below the cut! :-) Continue reading
My perfect Saturdays start like this: Early morning walk along the water, followed by coffee while blogging about waves. Today’s focus: The cool waves that birds make!
First, let’s look at the weird way in which seagulls take off from water. They make a big splash which develops into ring-shaped waves. So far, so good. But…
…that’s usually not all that happens: They usually hit the water a couple more times before they fully take flight, thus leaving a trail of circular waves radiating from each of the points where they hit the water.
This morning, there was a seagull sitting very close to the sea wall (which you see in the lower right corner of the picture), probably eating or washing its feathers; in any case radiating off waves. When I looked down, it flew up, hit the water once, landed again, and then began to swim away.
And you can see all of this in the waves!
The green cross below marks the spot where the seagull sat before I interrupted it. It must have been sitting there for a bit judging from the radius of the circular waves marked in green that radiate from that exact spot.
But then when the seagull saw me, it took off, dipped once into the water (green cross and corresponding wave circle), and then landed again (red cross) and swam away from there (following the red arrow on which the centers of the red circles fall).
How cool is this?
Once it was just swimming and not dipping in and out of the water, it begand to develop a regular, v-shaped wake (red V) that consists of individual “feathers” or wakelets (yellow).
It continued swimming away, albeit taking a little turn…
You still see the green waves from where it was sitting originally, and then the red waves from where it landed and swam away on the path marked by the red arrow.
This kind of stuff makes me so happy! :-)
From the waves in the picture below, can you tell me what that seagull did before the picture was taken?
Yay! Another recap of my wave watching Insta!
The year started off in the very best company — watching ships and waves and flowers with Astrid!
But of course there is also actual wave watching happening: Here we see a ship’s wake arriving. I find it fascinating how there are the stripes where you can look into the water and then those where you can’t! Total reflection in action. When I learned about that in physics class I never thought that was a phenomenon I would ever see in real life!
When the waves from the picture above meet the curved sea wall, they get reflected into this pretty pattern.
Another day, foggy and very windy! That day, my focus was on how there are no waves in the lee obstacles. Only after sufficiently long fetch do waves start to grow.
See how the surface roughness changes with distance from the obstacle?
Oh, and then there was a sunny day! The Oslo ferry is leaving in the distance. See the stripes in different blue tones? In the foreground you can see how the colors are related to surface roughness. Areas that are more exposed to wind are rougher with more waves and different wavelengths, and look darker. More sheltered areas in the lee of structures have fewer waves and appear in a lighter blue.
Oh, and then I had a great day with my nephew in the port of Hamburg with harbour boat trips, walks on the beach, and tons of wave watching. He was very impressed by my skill to know how far each wave would run up the beach, especially since we saw lots of people who either ran away screaming or got wet feet :-D
Another picture from the same day with my nephew: Here is a wave train from a ship’s wake arriving at the beach. I love watching this kind of stuff!
And then one day, I went#WakeWatching! On all three pictures below, you see waves made by the same little ferry. On the right is the turbulent wake where the ship just moved through the water, and on the left some of the feathers that form the V.
Here the ship is turning so we see water that is disturbed by the ship moving through, but doesn’t have the „boiling“ like where the propeller stirred up everything.
Now we see how the wind waves seem to be bunching up at the boundary between the wake and the area that wasn’t affected by the ship moving through.
Then, for #SciCommSunday, I posted a picture of a book that I think is a brilliant introduction to the science of communicating science that I also wrote a blogpost on.
And surprise: Bonus pic for my dear readers that I didn’t post on Instagram but that I think is cool (will definitely experiment with this kind of pictures more! Except panorama mode does weird things to waves, so on second thought maybe not…)
What we are looking at in the picture above is a really low-water day in Kiel. Which leads to interesting wave watching opportunities!
See how waves that arrive with straight crests somewhere offshore get bent as they reach the shallow water? That’s because the velocity of a wave depends on water depth. The deeper the water, the faster the wave can move. The shallower the water, the more the wave is slowed down. Therefore, waves get slowed down first in regions where the water is shallower, and the parts of the wave crest that are still in deeper water wrap around the shallower part. Kinda like when you are slipping on an icy road, you fall in the direction of the foot that didn’t slip because your body spins in that direction.
When there is really low water in Kiel fjord, we can observe the influence of topography on waves much better than we usually can! For example here we see how on one part of the “beach”, there are several wave crests behind each other, all breaking, whereas on the other part on the other side of the headland there is only one wave crest at the water’s edge. Why is that?
Wave crests get steeper and start to break when the water is shallow enough for the wave to “feel” the bottom. On the left side of the picture, depth is increasing faster towards the open ocean: The wave only feels the bottom right before it has reached the water’s edge. On the right side of the picture, on the other hand, the depth changes very gradually. Therefore waves feel the bottom already much earlier and many wave crests are steepening, preparing to break and finally breaking at the same time.
And then I just thought this picture was fun :-)
And a rainy day at work!
I actually don’t mind all the rain: It makes the flow in all the storm drains so much more interesting! Here we see how water shoots out of a pipe into a little lake. Note that I’m saying the water is shooting rather than flowing: That means that it is moving so fast that any disturbance is washed away with the water.
As the water shoots into the much slower flowing lake, it pulls water from the sides with it. This water obviously needs to be replaced from further away, so a recirculation is set up.
Here is an annotated version of the picture to see the recirculation going on:
So that’s what has been going on over on my wave watching Insta @fascinocean_kiel! :-)
On the GEOF105 student cruise that I was lucky enough to join like I did last year, I happened to observe what you see in the picture above: Standing waves in a bucket! And this isn’t a staged photo, this is me taking a picture of a student at work.
We are looking at the bucket the students use to take surface water samples which they measure on deck. The bucket happens to stand just above the engine room. Which leads to vibrations. Which, in turn, leads to waves. Many different kinds of waves! In addition to what you see above, we find, for example, plain circular waves. They might look like they do in the picture below:
And here is a short movie of the waves, first in real time, then in slow motion.
Sometimes the circular waves also have other wave lengths.
The next pattern that develops from a monopole (like the one you see above) is my favourite: A monopole with higher order stuff developing at the edge of the bucket.
Watch the movie below to see it in motion (first at real speed, then in slow motion).
The next step, then, is water that almost looks as if it was boiling. Like so:
Here is a movie of the bucket with the “boiling” wave pattern, again in real time first and then in slow motion.
The movie below shows a close-up of some of the waves in the “boiling” state, when there was enough energy in the system to throw drops up in the air. The movie goes from real time to slow motion. Careful when you play it, I left the sound in in order to show how the frequency of the waves is the same as the frequency of the engine. (And because of the annoying sound, it doesn’t start up automatically, so you have to click to play)
Here is a movie that shows the bucket in different positions, shot continuously to show how quickly the wave pattern develop and also how close together the different spots with the different pattern are located. Thanks for playing along, Kjersti!
So clearly the location has an influence on what wave pattern develops. But what are other important factors? We tested material, shape and size of the container.
A small plastic bucket which is almost cylindrical, for example. Guess what happens?
We can get the same wave pattern as in the large bucket! The movie below shows three different wave pattern. When the frequency suddenly changes that’s because the movie is in parts played in slow motion.
As to material: It seems to be important that it’s flexible. Iron cast pans don’t work (yes, there is water in it!), neither do metal lunch boxes…
And round shapes make nicer waves. But the rectangular vanes of the surface drifters (aka paint roller trays) also make pretty pattern! But now the waves are, unsurprisingly, only parallel to the edges of the tray.
Yep, this is the kind of stuff that makes me really happy! :-)
Even though I’ve been looking at waves for years now, wave watching is still full of surprises. Yesterday I showed you capillary waves that a jellyfish made, and today I’m showing you a helpful seagull.
What I found most fascinating walking through this marina were the long straight wave crests that form in parallel to the step in the foreground as waves leap up on the step and then the water flows back. I can watch this kind of thing for a very long time!
But I was also pointing out the ring waves around the bollards to my friend, which are a lot more difficult to spot. But, as if it had just been waiting for the opportunity to help out, the seagull on one of the bollards dropped something and created ring waves for us! Can you spot it?
We saw Piel Island with a very cool castle ruin across the bay when visiting the South Walney Nature Reserve the other day, and were intrigued by it. Depending on the tides, you can drive over by car, walk, or take a ferry, which is what we did.
Arriving at the spot where the ferry was supposed to leave, we were greeted with this beautiful sight: A pier going down into the water, creating beautiful wave pattern in the strong incoming tide! We see a hydraulic jump similar to the one we saw on Walney Island, except that this one is even cooler: It happens in the area where the pier is just below the water surface, but a strong current goes underneath the pier on the land side as soon as it is above water level.
Above, you see the current going left-to-right, creating a lot of turbulence where water comes out from underneath the pier (see those eddies where the water looks as if it was boiling?). You also see the waves hitting the pier on the left side, and then standing waves towards the right of the pier, locked in place because they are propagating upstream with the current’s exact velocity, thus staying in place (aka “standing”).
This is super fascinating! To me, anyway ;-)
Once on Piel Island, there is a lot of really cool wave watching to be done, too.
Below, you see waves reaching the island and “wrapping around it” — i.e. being refracted towards regions of lower velocities, which means that they will be bent towards the shore, no matter which direction they originally came from.
You can observe this for quite a big part of the island as you walk around it! The original wave direction is the one seen in the bottom left, all the rest of the wave field has been refracted by the change in water depth!
But obviously there is a limit to how long you can play this game. Below, you still see waves wrapping around the island, but they aren’t reaching the shore more or less parallel to it.
But even just watching all these crests break, one after the other, along the shore looks pretty cool!
But, obviously, if waves get wrapped around an island, but not completely, there must be areas where wave fields going around either side of the island meet up at an angle to each other. Like here:
And once again, this time moving:
And another very good spot to see this kind of pattern is a little headland like below:
Can you spot the distinct checkerboard pattern of the waves, and see how they break where a crest meets another crest?
I can watch these kind of things forever without getting tired of it!
And once more, as a short movie, because waves are even more awesome when they are moving:
Or waves more generally, especially breaking waves.
How beautiful is this?
I can really watch waves for hours without getting tired of it.
But anyway, walking further around the island, here is a spot with fewer waves: Here we are in the lee of the island, the area that is sheltered from the wind by the island itself.
Oh, and this is the ferry that got us over to the island. As you might notice below, the current has turned and is now going out — unfortunately I didn’t take another video or even good picture! But you see the edge of the jetty in the lower right, and the current downstream of the obstacle with a very different surface texture than the surrounding water. And then there is always next time… ;-)
On our way back home, we stopped for scones and coffee (sorry, no tea) and had the amazing views you see below. These channels don’t look dangerous by themselves when they are empty, but thinking back to how quickly the tide comes in around here they don’t seem as harmless any more, do they?
But oh so pretty! :-)
Arnside is a beautiful little town on the banks of the river Kent, and Astrid and I went on a nice hike along the shores of the estuary a little while ago.
The difference between high water and low water is quite impressive here, and we started our hike right after high tide to make sure we wouldn’t be cut off by an incoming tide. Which was definitely the safest thing to do, but also made for pretty muddy shoes…
There is a ton of amazing wave watching to be done in the Kent river bed. For example the waves being diffracted around these rocks.
Or this diffraction at a “slit” between the rocks.
And the whole landscape is just gorgeous!
Very intriguing to me: A foam stripe that seems to be coming out of nowhere. Or, better, that we can’t see the cause of just yet. It’s coming from somewhere downstream (to the left).
But where is it coming from? From somewhere behind that headland. Let’s go inquire!
A little further down the coast line, we see that the foam stripe ends on a sandbank.
And coming closer still, we see that the foam is created by waves breaking on that sandbank and a second one a little further offshore. It gets collected where the bank brakes the water surface, and is then just driven downwind, but stays together, forming the stripe.
This is a closer look of the waves breaking on the sand banks.
And speaking of sand banks: There is some cool wave action in between the sand banks, too! Waves are driven in by the wind through the channel from the left. This is a clearly visible wave field with larger wavelengths and heights than the rest of the small basin, where waves are only created locally once the wind reaches the water surface. See how on the left edge of the basin the water is sheltered from the wind by the higher edge of the sand bank?
Again, what a pretty landscape!
I really like the contrast of the lush green grassy areas and then the sandy muddy tidal river in the background.
Walking a little further, we now see a large muddy area. When we were walking here, a local told us that when he was a kid, all this area was also grass land and it only became sandy and muddy a couple of decades ago. Fascinating how the landscape changes!
But even on timescales of hours the landscape changes, and all the sandbanks and channels move with each incoming and outgoing tide.
It’s so beautiful here!
Our walk took us away from the water and up a little hill, but that gave us the opportunity to look at the channels from a different perspective.
And even the whole estuary. Do you see the rail bridge below? That’s the one we saw in the very first picture of this post.
Back in Arnside, we are approaching low tide. Which means that we have lots of freshly exposed mud with new ripples in it, as well as still water running off it. Below you see a really cool turbidity current coming out of the channel with the seagull, going into the larger reservoir. See how it carries mud with it and how the channel is meandering and clearly changing right in that moment?
Another picture, just moments later, and already has the shape of the channel changed!
Or the edges of this little basin that get exposed little by little as the tide goes out.
And then there is of course more wave watching to be done. See how this wave changes direction as it runs around the little headland?
And thanks to two kids playing in the water, we get even more waves where they threw a ball into the little basin.
And those waves spread over time…
Checking in with the seagull and the turbidity current again. See how much dissolved mud is being washed out all the time?
And as you might have guessed in a tidal river like river Kent — there is even more to see. Which is why we came back a couple of days later to see what all the warning signs were about…
I’ll tell you about that tomorrow!