Diffraction of waves around obstacle

I have always really liked the artwork you see below that was installed in Store Lungegårdsvann when I still lived in Bergen.

But on the pictures here you also see how awesomely waves are diffracted around it.

Pretty and interesting oceanography? What’s not to love? :-)

The blogging hiatus


You may or may not have noticed that my usually very regular blogging has been sporadic at best for a while, and that currently I am blogging a lot more again. Do you want to know why?

You might know that I am currently working in science communication research. And one of my current research interests is how science blogs contribute to science outreach, specifically what motivation bloggers have for writing blog posts, what their goals are with their blogs, and how they determine whether their blogging is successful.
And while doing a literature review on that topic and thinking more and more deeply about it, I have come to realize all the ways in which my blog doesn’t match the design criteria from the literature, nor my goals as a science communicator guide my writing style or my choice of topics. For a while I struggled with that — if I am thinking about blogging so much anyway, shouldn’t this blog be a best practice example so that other people don’t have to read scientific literature about blogs as I do, but can just read my blog and take on whatever they like about it? And shouldn’t I have clear goals in terms of learning outcomes connected to my blog? Or define a persona, a typical user, that I am writing for? And, seeing that I spend quite a lot of time on this blog, shouldn’t it have an impact, spark thoughts or discussions, make the world a better place?
When I started thinking about the persona thing, I realised that I know who is reading this, and who I picture when I am writing. Hence I know who I am writing for: For my oceanographer friends, who like looking at oceanography from my perspective and who enjoy seeing the wonders of oceanography on a puddle or in a plastic cup. For my non-oceanographer friends who find it interesting that there are people weird enough to be this fascinated by water. For my family who is still reading this.
And finally I realised that I don’t really care that this blog isn’t a best practice example for science outreach. Because that’s not my motivation for blogging on this blog (though it is on others). And that not every minute of my waking time has to have a tangible outcome — sometimes it’s ok to just do something as a hobby with no purpose other than enjoying the process.
I am writing here because I enjoy writing and curating a collection of my photos, because I want to have an easily-accessible archive of my thoughts on and pictures of water, and because I like sharing this with my friends and everybody else who is as fascinated by water as I am. But first and foremost, even though I am happy to share it with anyone who enjoys it and even though I am super excited to discuss water with anyone who is interested, this is my blog that I write for myself, not for any audience and for no other purpose than that I enjoy doing it.
And I guess once the pressure of writing a best-practice example blog was off, it became so much more fun again, and now we are back with full force! :-)

Traces in the sand

Yes, I am really that fascinated by sand that this is the second post in a week about it.













And I still think the picture below looks like the place in Qumran where the Dead Sea Scrolls were found!


Locks at Kiel Canal

The locks at Kiel canal always make for interesting weekend strolls. I love watching ships!

Especially armed with my favourite app, VesselFinder (similar to marine traffic described here), because it let’s me anticipate which ships will come next.

And because I love my new hat! :-)

Melting ice cubes & thermal imaging camera

I haven’t talked about my favourite experiment in a long time (before using it last week in the MeerKlima congress and suddenly talking about it all the time again), because I felt like I had said everything there is to say (see a pretty comprehensive review here) BUT! a while back my colleagues started playing with a thermal imaging camera and that gave me so many new ideas! :-)

I showed you this picture yesterday already:


Here we see ice cubes melting in fresh water and salt water (and my very fancy experimental setup. But I am pretty proud of my thermal insulation!). Do you know which cup contains which?

Here are some more pics: The ice cubes before being dropped into the cups. Clearly dark purple is cold and yellow/white is warm (see my fingers?)


After a while (5ish minutes), the cold meltwater has filled up the bottom of the freshwater cup while floating on top of the salt water cup:


Looking in from the top, we see that the ice cube in salt water hasn’t melted yet, but that the other one is gone completely and all the cold water has sunk to the bottom of the beaker.


When you check out the movie at the bottom of this post, you will notice that this experiment doesn’t work quite as well as I had hoped: In the saltwater cup, the ice cube floats against the wall of the cup and for quite some time it looks like there is a plume of cold water sinking in the salt water. I’m not quite sure what’s going on there. If it’s showing up like that because the cup is such a good thermal conductor, then why is the “plume” directional and not spreading in all directions? If there really is a plume, then how did it get there? It shouldn’t be! So many questions!

There really can’t be a plume of cold melt water in the salt water cup. For my workshop last week I made the plot below (which, btw, I don’t think anyone understood. Note to myself: Explain better or get rid of it!). So unless the plume is cold salt water, there is no way anything would sink in the salt water cup.


So maybe we are cooling the salt water around the ice cube which then sinks and shows up because it is close to the wall of the cup? We can’t look “into” the cup with a thermal imaging camera, we can only see the surface of the cup (See, Joke? Maybe it is useful after all to learn all that stuff in theoretical oceanography ;-)). That’s also why we don’t see a plume of cold melt water in the freshwater case like we see when we have dyed ice cubes and see the melt water plume, like below:


Anyway. Here is the video, in which you sometimes see my finger, pushing the ice cube away from the beaker’s wall to finally get to a state that looks like what I wanted to show you above:

Playing with a thermal imaging camera

Today I’ve been playing with a thermal imaging camera. Below you see a snapshot of my experimental setup, but before I tell you more about that experiment, a little bit of playing around.

See my reflection in my porthole below? (Btw, how awesome is it that I found a porthole to decorate my living room with???)


That reflection also shows up with the thermal imaging camera.

And since I was taking pictures of myself: Here I am with “ice-cube make-up” and glasses that I had taken off for a while and then picked up again just before taking that picture. Do you see the endless possibilities of playing with a thermal imaging camera?

My workshop at

Today I ran a workshop at the congress in Hamburg: A congress for high school students, organised by a student committee. The large lecture theatre of the chemistry department at the University of Hamburg was crowded for the opening lecture by Mojib Latif:

For my workshop, however, we set a limit of 40 participants due to the size of the room (and the amount of stuff that I had lugged in from Kiel. Yesterday’s ice cubes did very well, btw!). And there were two TV crews and a photographer documenting the awesome ice cube experiment.

You can watch documentaries of the workshop here and here (both in german).

Sneak peak of those two documentaries, obviously only of the tiny little sequences featuring me:

And thanks to Johanna and Dirk for their support before, during and after the workshop!

I also got to watch another workshop by a colleague, who used the Monash Simple Climate Model (which I have talked about here) and I have got to say: That is such an awesome tool for teaching about models and/or the climate system! You will definitely hear more about it in the future as I incorporate it into my own teaching.

And last not least we had a phone call to the Meteor off Peru which rounded off a day full of bumping into people I hadn’t seen in a while. Always great to reconnect with old friends and colleagues!

It was great fun to be part of this congress, and it was a great way to experience first hand how science outreach can work in such a format. Since the congress was curated by the students themselves, many students were very interested and asked great questions. Also, the topics of the workshops corresponded closely to what students really wanted to see and hear. It would be amazing to see this scaled up next year, maybe over several days and with more parallel sessions, so that participating students really get to pick and choose exactly what topic they are interested in and that even more students get the opportunity to experience such an amazing congress!

Shallow water waves

Have you ever noticed how, if you are at a shallow beach, no matter how choppy waves are further offshore, everything becomes nice and orderly on the beach?

Below you see where the water depth suddenly increases, both from the color of the water and from the wave pattern. While in deeper water waves propagate at all kinds of speeds depending on their wavelength, the moment the water becomes shallow enough, all waves propagate at the same speed (except for the really short waves for which the water is still deep, but let’s forget about those). If all waves propagate at the same speed, it means that the form of the wave that we observe stays constant over time and just moves as a whole. Hence it looks a lot more tidy than the choppy waves further out.

Funny that in all these years of wave watching, I have never thought about that before!

Watch the movie below to see for yourself