Tag Archives: Store Lungegårdsvann

#BergenWaveWatching: observing waves and tides on Storelungeren

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Reposted from Elin’s blog:

Kjersti, Steffi, Elin and myself (Mirjam) recently discussed ways to better integrate the GEOF105 student cruise into the course. My suggestion was to ask the students to observe things throughout the whole duration of the course, and then have them relate their time series with what they observe when “at sea”. In this mini series tagged #BergenWaveWatching, I write up a couple of suggestions I have for observations that are easy and fun to make. I am anticipating that my suggestions will be strongly biased towards #wavewatching, so if you have any other suggestions, I am all ears! :-)

Really close to home today! Nygårdsbruen.

Where to go

Nygårdsbruen — the bridge right next to GFI

When to go

Whenever you are going to or leaving GFI anyway works fine, especially if that happens to be at around the same time every day

What to look out for

That kind of depends on how regularly you will realistically be able to go there. If you are there several times per week, you could look at the tidal current. Which direction is it going in, how strong is it, what’s the water level like, …?

If you aren’t going as often, maybe focus more on a general description of what is going on. Is there a tidal current visible? Is it going in or out? Does it have an influence on the wave field? What other factors influence the wave field? What’s the wind direction? Can you see areas that are sheltered from the wind and areas where the wave field is more developed? Can you easily look into the water? Where, and where not? Why is that? That kind of stuff.

The current acts as a barrier to wind-generated waves. How cool is that? Blog post on this here.

What to do with the data

By “data”, I mean the collection of pictures on your smartphone. You could, for example, relate them (thanks to the phone’s time stamp on the pictures) to time before/after high water as I did in this post for tides on the Elbe river in Germany. This of course doesn’t account for the spring/neap signal, which you might want to include.

Questions that I find interesting: When is the strongest current actually happening relative to high water, and within the spring/neap cycle? In what way do ingoing and outgoing currents differ (and why? Shape of the landscape? Different gradients in the water level? …)?

Or, if you don’t have a lot of data from different days, describe what you see (maybe similarly to what I did here).

Looking towards Storelungeren. See there are at least four different areas of what you see on the water? (Being able to look into it clearly, being able to look into it where shaded by the bridge, reflection of the other shore, rough surface due to wind waves)

How this is relevant for the student cruise

One task on the GEOF105 student cruise is relating trajectories of drifters to several factors. The wind field on that day, for example, but also the tidal currents in byfjorden. So having a good intuitive understanding of tides makes interpreting the drifters’ trajectories a lot easier, even though the drifters will be deployed in a different area.

More generally, this suggestion is about repeatedly observing a very easily accessible body of water and looking at how it looks different each time. This is good practice of observational skills, and also eye-opening to the many ways in which a body of water can look different at different times — different times in the tidal cycle, different seasons, different weather, especially different winds.

Do you have suggestions for us? What other spots or topics would you recommend in and around Bergen to be added to the #BergenWaveWatching list? Please leave a comment! We are always looking to expand this list!

Even on a no-waves day, Store Lungegårdsvannet is one of my favourite #wavewatching spots

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I love how below you see the sharp edges of where the bridge’s shadow makes it possible to look into the water, when it is impossible to see anything where the sky is being reflected. But you see the equally sharp edge of the reflection of the mountains on the other side where you can’t look into the water. Isn’t physics just amazing?

Also I don’t know what it is, but I really like this perspective on the bridge :-)

Fascinating how the same body of water can show up in so many different colors at once!

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Stupid as it sounds, one of my favourite wave watching spots in Bergen is a busy bridge with a view onto another busy bridge. But the bridge goes across a very narrow opening which connects Storelungegårdsvannet, which you see in the pictures, with a fjord and ultimately the open ocean. As the opening is a lot narrower than both the fjord and the lake at the fjord’s head, there are pretty much always strong tidal currents going one way or the other, sometimes leading to a substantial difference in sea surface height on either side of the bridge. I found that quite scary the first couple of times I had to paddle through!

But what I found most fascinating today is how many different colors you see on the water, and how they are all explained by different physical processes.

If we look at the bottom end of the picture above, we see that we can look fairly well into the water and see the sandy/rocky bottom with some algae growing on it. You can look into the water so well because several things came together at the time when I took the picture:

  • There weren’t a lot of waves to disrupt the view
  • I’m looking into the water at quite a steep angle, so even though the light going in and out of the water is refracted at the interface, the angle is too steep for total reflection to happen
  • This lower area of the image is reflecting the dark underside of the bridge rather than the bright sky, making it easier to see the muted colors in the water because there isn’t too much interference with bright colors from elsewhere

Moving on a little up in the picture above: Here we see the reflection of the sky (see the clouds reaching down the slopes of the mountain? (If you don’t see what I mean, check out the image at the top of this post where you can see it both reflected and “for real”)

We see the reflection here because the angle is a lot shallower and we don’t have the bridge’s shade making it possible to look inside.

Notice how the bridge’s reflection doesn’t have a sharp edge but shows up all the turbulence in the water? You can also notice more turbulence on the right side slightly above the middle of the image.

And then there is this grey stripe going all across the reflection of the mountain and houses. That’s where a little breeze is going over the surface, creating ripples. Since the surface is rougher now, we get a lot of bright sky reflected towards us.

Below another image, where you see both sides of the bridge’s reflection. Isn’t it fascinating how turbulence is distorting the reflection? And there is a lot more turbulence on the left than on the right at the bottom end of the bridge’s reflection, where you can still make out the railing of the bridge in the reflection…

In the uppermost image, you also see that it becomes more and more difficult to see the bottom as water depth increases – the water seems to be getting greener and greener, darker and darker.

What else did you spot that I didn’t mention? And do you think you’ll look at Storelungeren the same way as before next time you cross that bridge? ;-)