This is neither “oceanography” nor “teaching”, but so much “adventure” that these pictures still deserve their spot on “Adventures in oceanography and teaching”. I did a tour into two (non-active ;-)) volcanoes and it was AMAZING!
Hi! I am Mirjam. We are investigating ocean currents in a 13-m-diameter swimming pool that sits on a merry-go-round. Ask me anything!
I will be hosting an “Ask Me Anything” event!
I am a member of Elin Darelius’ team of scientists. We are investigating ocean currents near Antarctica — by doing scientific experiments in a 13-m-diameter rotating water tank in Grenoble, France. Ask me how experiments in water tanks can tell us something about ocean currents; how we usually observe ocean currents from ships; what it is like to work with an international team in a foreign country; how you become an ocean scientist; anything else you want to know! Looking forward to hearing from you! :-)
To ask me anything, you can either leave comments below or head over to my page on OceanAMA and ask questions there. I will be answering them from Grenoble on October 18th!
“Observed vulnerability of Filchner-Ronne Ice Shelf to wind-driven inflow of warm deep water”*
Let’s talk ab’t a favourite paper
“Observed vulnerability of Filchner-
Ronne Ice Shelf to
of wa(-a-a-a-a)rm deep water”
An ice shelf is ice that is floating
on top of the sea as it’s flowing
down from a continent
this one is prominent
more ar’onl’ the Ross Shelf is coating.
In oc’nographers’ jargon, “deep water”
(as we learned by heart at my alma mater)
are defined by their propertie’
and live in the deep, deep sea
and currently they are getting hotter.
But “warm” is a relative measure
bathing in it would be no pleasure
it’s temperature typically
less than just one degree!
Go measure yourself at your leisure!
As winds weaken now during summer
warm water, like led by a plumber,
climbs up the continent
and can now circumvent
sills and reach ice from under.
If temperatures rise as projected
a lot of the ice will be ‘ffected.
Raising the lev’l o’ sea,
which needs to be further dissected.
Because of its climatic impact
which Elin has now shown to be fact
we need close observation
of deep water formation
so all changes can carefully be tracked.
*that’s the title of an article by (Elin) Darelius et al. (2016) which served as inspiration for this poem.
Whale watching on Terceira was A-MAH-ZING. We saw three different kinds of dolphins: Bottle-nose, common and spotted. But what you should really be doing once you are done swooning over all the pictures below: go over to Elin Darelius & team’s blog and read about what is going on with the 13-m-diameter rotating tank! :-)
This is what the way to and from the 13-meter-diameter rotating tank in Grenoble looks like (and you should really visit Elin & team’s blog to learn about all the exciting stuff we are doing there!!!)
And the best part is the Isère right next to the bike path:
And one thing that I find really impressive with this river (coming from a much flatter part of the world than Grenoble, where rivers aren’t typically as fast-flowing as the Isère) is how all these return flow pools form everywhere.
Watch the movie below to spot them yourself, or my annotated picture below:
It seems really counterintuitive that a strong current would make water on it’s side flow upstream instead of flushing everything downstream or even just going downstream through stagnant water, doesn’t it? But when I thought about why that is, it reminded me of the way a water jet pump works: You flush water from a tap down through a hose, and that hose is connected with another hose through which you want to suck something (usually some gas out of some container). So there it’s the same: The fast-flowing water pulls things in from the side and takes them with it. Now for continuity reasons, the water that is entrained in the jet needs to come from somewhere, so water has to be brought upstream in order to get sucked into the jet. That’s also similar to playing with Venturi tubes where the thinner the tube, the faster the flow, the lower the pressure… Anyway, riddle solved and I can think about other stuff again ;-)
But it is a really beautiful place to be:
I like water so much better than mountains, but mountains still have their charms, can’t deny that…
Tale of arctic melting and deep water formation
Freshwater freezes long before saltwater does,
and it also floats on top of saltwater.
In the Nordic Seas, deep waters are formed.
If there is a lot of freshwater,
less deep water can be formed.
The sea freezes over.
Ice then insulates,
prevents heat flux,
fresh water layers
are also the currents.
East of Greenland, to name one,
flows fast the East Greenland Current,
taking away all the freshwater
through the Denmark Strait south, and further south,
where the freshwater mixes with saltwater
until anomalies return decades later,
starting the circle again. Now what if Greenland melts?*
*I don’t actually have an answer to the question what will happen if there is a large input of freshwater into the Nordic Seas (which seems unavoidable under global warming when both Arctic sea ice and Greenland glaciers melt). My own research, interpreting measurements taken in the region between 1950 and 2000, shows that during that period the fresh meltwater got transported south, out of the Nordic Seas, as suggested in the poem (Glessmer, Eldevik, Våge, Nilsen, & Behrens, 2014). However, even the newest of those measurements are almost a decade old now, and the debate among experts about what will happen is wide open. Exciting times!
Today I went on a wave-hunt expedition to take pictures for posts on the Froude and Reynolds number over at Elin & team’s blog (which you should totally check out if you haven’t done that yet! I am actually proof-reading my posts there and that is saying something ;-))
Anyway. Let’s look at the picture below. Do you see how there are two qualitatively different flow regimes in the Isère? Closer to the banks, you see waves that look like normal waves, happily propagating wherever they want to. And towards the middle of the river, you see that there is a lot of turbulence, but disturbances don’t propagate wherever they want, they are being flushed downstream.
For comparison below a picture of a part of the Isère where it is turbulent all the way to the sides:
And below a nice example of how phase velocity of waves depends on wave length. See all the small, choppy stuff being flushed downstream and then standing waves caused by some obstacle in the middle of the river? That’s because the longer the wavelength, the faster the wave propagates (assuming that we are in deep water, which I think is a safe assumption in this case). So the river is so fast that the slower waves get flushed away and only waves of the length of those created by the obstacle (or longer) can stay in one place (or even propagate against the current). I think that’s pretty cool.
Below is one of my favourite wave-watching sights: A half slit.
And in the picture below, we can kinda see vortices detaching behind the obstacle (or is that just me)?
And what I really liked: see the spot below where there are all of a sudden standing waves appearing in the middle of the river? Clearly there is a sill below, but I like that you cannot see the obstacle, just deduce that it must be there from how the waves look :-)
It’s not a hardship to be here, I can tell you ;-)
It is quite a beautiful place! And, by the way, this is my 600th blog post on this blog. Can you believe this?
Today we have foam patterns again, but of a very different kind than usually:
I don’t know if I have just never noticed before (I can’t really imagine I would have missed that?), if it never happened when I have boiled eggs because I always boil my eggs with more bubbles and hence more turbulence, or if French eggs are just different from german eggs?
But living in this shared flat in Grenoble is proving to be quite educational. Not only have we learned that you should never wash eggs because that destroys some protective layer of “hen juice” (technical term coined by Nadine), we also learned that a peanut and a salted peanut have different names in French (l’arachide vs la cacahouètte), and that there are cheeses with a layer of ash in them.
But anyway, I don’t think it’s foam that comes off the eggs, I think it’s coming off the bottom of the pot. Because if those bubbles are raising up from the bottom, that would explain why there are more bubbles around the edges of the eggs (when they had to move around the eggs to get to the surface) than in between, and that there is hardly any foam above the eggs? Or what do you think?
And then, of course, we are learning all the cool oceanography stuff, too, and you can read all about it over on Elin’s blog!
You know I like tank experiments, but what I am lucky enough to witness right now is NOTHING compared to even my wildest dreams. Remember all the rotating experiments we did with this rotating table back in Bergen?
Those were awesome, no question about that. But the rotating tank I am at now? 13 meters diameter.
Yes, you read that correctly. 13 METERS DIAMETER!
I’m lucky enough to be involved in Elin Darelius & team’s research project on topographically steered currents in Antarctica, and I will be blogging on her blog about it:
In any case, don’t miss the opportunity to see what is going on in a tank this size:
Yes, they are both INSIDE the tank. Elin (on the left) is sitting on the tank’s floor, Nadine (on the right) is climbing on the topography representing Antarctica. For more details, head over to the blog!
Do you know the phenomenon that once you start noticing something, you see it everywhere? That’s been the case with me and total internal reflection. Not quite as impressive as last time, but still there:
And what I found really interesting this time: a swarm of tiny fishies making wave rings! I only noticed them because of those tiny waves. And if you look closely you can see so many of them just below the surface right where the wave rings are!
So funny to see the water almost boiling with fish on such a calm morning.
And another thing that fascinated me: how it’s so much easier to see into the water in places that are shaded (or dark) from the reflection of that pier. Not quite sure yet why it’s so much easier to see here, maybe just because there isn’t any glare? Any ideas?