Tag Archives: waves

How water changes coast lines

One thing I have been noticing a lot recently is how water changes coastlines (or even just paths in parks).

Not really surprising, considering the enormous amounts of energy stored in waves that are released on the beach every couple of seconds. For example in Hastings, UK, the shape of the beach looked different after every high tide of the three-day mini break we spent there. groynes, built there to prevent erosion of the beach, get buried in pebbles on one side and totally hollowed out on the other side.

Or, looking down towards the water:

And this doesn’t only happen to one particular groyne that was built in a particularly nasty spot, but to every one for miles and miles along the coast line.

This gives the beach a see-saw-like edge:

And this is what it looks like when waves arrive at the beach and meet groynes. Enjoy!

The enormity of waves

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It’s easy to forget the enormous size and power associated with waves in the ocean. Yes, we see pictures of surfers on Hawaii or of ships in waves occasionally, but usually we don’t really think about how large waves out in the ocean actually are. Which makes it easy to underestimate the force that the ocean holds within, not only on days when natural disasters like storm surges or tsunamis occur, but on a daily basis, just in the swell of distant storms. So sometimes it is quite healthy to look at waves on the beach and compare them to other buildings.

For example here, waves and Hastings Pier:

Those aren’t even particularly large waves, yet we see that their wavelength, peak to peak, is easily a lot more than 20m. This is what coastal structures deal with on a daily basis!

Waves in the clouds

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On my way back from London I had an almost equally interesting flight as on my way to London, which I talked about here and here. Except that most of the excitement this time round came from discovering that I wasn’t, in fact, sitting next to the person I thought I was, but that I was booked on a different flight from a different terminal. Which isn’t so terribly exciting in itself, but seeing that Terminal 5 is quite a distance away from the other terminals and the discovery itself happened at security some 20 minutes before boarding was supposed to start, it made for an interesting race across Heathrow.

But at least I ended up seeing pretty waves in the clouds:

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:

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).

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.

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

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

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

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

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

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:

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

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

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!

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

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… :-)

Foam stripes parallel to the coast.

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On my way to Heligoland the other day I noticed a phenomenon that I found really intriguing and that I should probably be able to explain. I first saw it on the screen of the boat’s web cams when we were about to leave the port of Hamburg. Unfortunately I could, at that point, only take a photo of the screen (but see how I excited I was to actually take a photo of the screen? ;-)).

Can you spot what I mean? Yes, that foam stripe running pretty much parallel to the pier! The place where it bends is right in front of our boat, which you see the railing off as that white stuff at the bottom of the screen).

But then, on Heligoland, I saw it again and became even more intrigued. Right in front of the place I stayed at, you could see it looking down the coast to your left…

…and to your right!

Here we can also see the stripe bending at some point, but here again the bend coincides with a change in the coast line. Similarly to what we saw in the port of Hamburg above, the stripe stays at more or less the same distance from the coast, so it is parallel while the coast is straight, and bends out when there are obstacles (like the catamaran above or the rocks below).

So how do we interpret the whole thing? I am not quite sure. I seem to have a very vague recollection that it should have something to do with half a wave length of the dominant wave, and foam collecting in a node point. And that makes sense intuitively. Except that I have several (ha! understatement of the month) minutes of video footage of the above, and I cannot for the life of me spot anything that would explain the stripe. If it is a node point, it is a very well-disguised one and I am surprised the foam can find it!

But there must be something different about that location than about all the other places closer to or further away from the coast. Any ideas, anyone?

A touristy post about my trip to Heligoland

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I recently went on a trip to Heligoland, Germany’s only island that is far away from the mainland (70 km in this case). It was a great trip, and I know you’ll be reading about it for some weeks to come :-)

Today, we’ll just do the touristy parts, though, and get into the oceanography later.

The trip started out super awesome. I went on a ferry and got the chance to see ships being greeted by Wilkomm Höft, the Ship Welcome Station, by dipping the Hamburg flag and playing the national anthem. I’ve seen this before, but only from land (this is a place that I love going to for birthdays, mine and other people’s). Sitting on a ship and being bid farewell this way is really touching! I loved it and got a little teary-eyed.

Being bid farewell (by dipping the Hamburg flag and playing music) at Wilkomm Höft in Wedel on the Elbe river.

The ferry itself is a high speed catamaran, which, as you might have guessed, produces an amazing wake.

Wake of the Halunder Jet, the high-speed ferry going from Hamburg to Heligoland.

Unfortunately, the ship is set up such that the rescue boats obscure the view of the wake a little. How inconsiderate ;-) Please ignore the outboard engine…

On Heligoland itself, there are the famous red cliffs, and tons of birds. Let me just show you a few:

Heligoland

The best-known part of Heligoland is the Lange Anna — a red rock called “long Anna”. You see it on the picture below. What I liked most about it — besides the beauty of the rock and the birds, obviously — was the wave breaker build there to protect the coast, and what it did to the waves.

“Lange Anna”, the famous red rock on Heligoland in the German Bight

Zooming in on the wave breaker’s edge, there is clearly very strong winds coming around that corner:

To be fair, it was a super windy day.

They also have a very nice beach on Heligoland, where you can see the bending of waves due to changes in topography that we talked about before.

And if you look over to the second island, you can very nicely compare and contrast the upwind and downwind coasts of islands:

See how there are lots of breaking waves (well, you probably only see the foam) on the upwind coast of the island in the back of the image, and how there are absolutely no waves in the lee of the sea wall in the foreground of that picture?

Btw, the downwind side of that same second island looks also a lot calmer as it is sheltered by the island itself:

Unfortunately, I couldn’t take a picture of the whole island at once, I really need to upgrade my camera… But can you spot the rainbow above?

Also there is some more, pretty spectacular weather to be seen:

If you go over to the other island, there are TONS of seals. Like several hundred, right on the beach! Obviously, I only have pictures of seals when there are also nice waves happening at the same time :-)

Oh, and birds.

And more seals! This one is cute, I have to admit…

Oh, and I was lucky (lucky means bold enough to ask!) enough to hitch a ride on the local research vessel, Aade. Below, they just finish a plankton trawl. We weren’t allowed out on deck because the weather was so rough…

What looks like a calm and serene morning really wasn’t one. It was super windy and wavy! Good thing I don’t get sea sick.

It turns out it’s super difficult to take pictures of waves that look as impressive as the waves are in reality. I really need to learn how to do that! But even if you don’t see the size of the waves, at least you get a different look at “lange Anna” below.

And these are white caps on the “open” sea, not waves breaking on a shore.

And for a nice comparison: The Aade (the research vessel I was on) and the catamaran that took me home later that night.

Anyway, it was a great trip!

Looking at how waves are bent

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As soon as waves run into water that becomes shallow enough for the wave to “feel” it, the waves start changing how fast they propagate. And depending on the shape of the topography, this often means that the waves change direction. This is called refraction and we can see it on many many different scales.

On a large scale, we see the wind waves coming down a fjord with long, straight crests, therefore not influenced by the sea floor yet . But when those waves come close to the shore, they start feeling the sea floor and react to that by being bent towards the shallower depth:

Below, I have drawn the wave crests I want you to focus on:

Straight crests coming in from the left, and then bent crests running into the mouth of the little bay to the right. Seeing it put like this, this might actually also be diffraction if we think of the mouth of the bay as of the widening behind a slit that the waves came through. Oh well.

But the same thing can also be seen on smaller scale, for example in the bay shown in the picture below. You can see some of the topography through the water, and you can infer some more: Wherever sea weed breaks the surface, water around it is probably shallower than water a little further away. And when you look closely, you can again see the waves reacting to the topography.

Similar thing again below:

Btw, this little bay is the one you see on the right of the picture on top of this blog post!

And it is not only physics of water that make this place super interesting: repeat after me, Ib: Anemones! :-)

Although it is pretty cool to spot more wave processes, like for example the wind shade — no waves phenomenon.

Again on large and small scales:

And you see the interference of waves coming round either side of those tiny “islands”.

Or just look at the beautiful blue water, the fjord, the snowy mountains in the back…

Or at something completely different: The salt rings that remain when rock pools fall completely dry.

Anyway, I love it here. Thanks, Elin, for having me again!

More wave-spotting in “urban environments”

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I recently started looking at waves in “urban environments” (in contrast to “on the sea”) with a new found fascination. The reason why will be revealed soon, but for now just know that there are more waves coming up on this blog!

Today, let’s start by looking at more waves on Store Lungegårdsvannet, like we did before.

Here, you look downwind and see the flat water right in front of you, shaded from the wind by the walls around the lake. And then the further away you look, the larger the waves grow.

Another very funny picture of a similar situation below: See how parts of the lake’s surface reflect the buildings and mountains and clouds really well (since that part of the surface is really flat), whereas other parts are way too choppy and appear a lot greyer on the picture?

Yes, I admit, the purpose of this blog post was not so much to talk about waves as to show you how beautiful Bergen is in May. I miss this city… And my AMAZING Bergen friends!!! <3

Walking around a lake to look at waves from all sides

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The most awesome thing about being on vacation is that I have the time to stare at water as much as I like.

For example the other day, I walked around Lille Lungegårdsvannet on a windy day.

Looking downwind, one sees a very smooth surface right in front of us, and then waves start developing further away. Looking at the fountain, you see that it is actually pretty windy.

Lille Lungegårdsvannet in Bergen

Walking a quarter of the way around the lake, we now look at the fountain at a 90 degree angle to the wind: it is blown over to the right. We now see wave crests traveling and see the shape of the waves much more clearly.

Lille Lungegårdsvannet in Bergen

Walking further, we see the waves coming directly towards us; the fountain is also blown in our direction. All of a sudden the water looks a lot more rough. And of course it feels a lot more windy, too, when the wind is coming right towards us and not in our back.

Lille Lungegårdsvannet in Bergen

And bonus picture: A rainbow in the fountain when we’ve gone 3/4 of the way around the lake. Beautiful day in a beautiful city!

Lille Lungegårdsvannet in Bergen

Adventures in Oceanography and Teaching

Dr. Mirjam S. Glessmer

Tag Archives: waves

How water changes coast lines

The enormity of waves

Waves in the clouds

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

Foam stripes parallel to the coast.

A touristy post about my trip to Heligoland

Looking at how waves are bent

More wave-spotting in “urban environments”

Walking around a lake to look at waves from all sides