Tilting the ice shelf! Or: Our experiments are getting more realistic

Posted on by Mirjam Glessmer

Until now, we have used an “ice shelf” (a plastic box) which had a horizontal bottom (Read more about the general setup of the experiment in Nadine’s post). The bottom of the ice shelf was either right at the water’s surface, or lowered down into the water. What we see then is shown in the gif below, where we are scanning the full water depth from the bottom upward. The ice shelf is resting on the upper edge of the v-shaped channel, so it effectively blocks the flow, which separates at the ice edge and turns mainly left.

Now it’s time to get used to a new vantage point, which lets us look underneath the ice shelf. The source isn’t in the upper right-hand corner any more as it has been in all images and movies on this blog until now. See the sketch below: The source is in the upper right-hand corner and the ice shelf sits in the lower center of the picture, across the v-part of the channel.

The gif below shows the same experiment that we saw before, only this time from a similar perspective as shown in the sketch above: When the flow reaches the ice edge, it is blocked and turns to the side.

But then today, we have started tilting the ice shelf (well, Adrian and Thomas have, as you see in the image on top of this post, but I will keep saying “we”).

This might be more realistic — an ice shelf would probably have melted more the further out into the ocean you look (where the ice would have been exposed to melt longer and also the currents flowing under the ice shelf would still be warmer), and therefore we would expect the base of the ice shelf to slope up the further towards the open ocean you go. But this circulation is also one that is easier to understand theoretically: We are expecting the current to stay on lines of constant potential vorticity*. But it can only do that if those lines exist. In the previous experiments, there is a jump in potential vorticity introduced by the edge of the ice shelf, since the water depth decreases drastically as the current meets the ice shelf. Therefore there is no obvious way for the current to take since it can’t conserve its vorticity no matter where it goes (which is why we saw most of it just bouncing off the ice edge and flowing away to the sides). Now, we were hoping to see a circulation where the current, reaching the ice edge while it is flowing approximately half way down the slope, would be guided down the slope as the ice comes further and further down into the water, until at some point it crosses the deepest point of the slope, and turns backward, flowing up the slope and towards areas where the ice isn’t reaching as far down. That way, the water depth the current feels would always stay the same, since it is moving up and down the slope to compensate for the change in height introduced by the ice shelf.

So here is a gif of an experiment where the ice shelf is tilted such that its edge on the source-side is at water level, while the opposite edge rests on the edges of the canyon.

In case you can’t spot it, here is a sketch of the circulation:

So what I described above is actually exactly what we observed! Very very exciting! 🙂

*For a quick explanation of vorticity see this blog post — quick and dirty explanation is that if water depth changes, a water column will change its rotation. Either by moving to a place with a different planetary rotation (but it can’t do that in our tank, see here), or by starting to rotate itself and hence changing direction

What would you like to know about our experiments with a 13-m-diameter swimming pool on a merry-go-round?

Posted on by Mirjam Glessmer

On Wednesday, October 18th, we are going to answer every question we’ve been asked until then and on that day.

What would you like to know? Leave a comment here on the blog, or on Facebook, or on reddit, or on our #OceanAMA. Or email us, tweet, just get in touch! Ask us anything, we are looking forward to hearing from you! 🙂

And do you know someone who would just love the chance to ask us anything? Then please share this post with them!

Investigating ocean currents in a rotating swimming pool

Posted on by Mirjam Glessmer

Reposting from Sci/Why “where Canadian children’s writers discuss science, words, and the eternal question – why?”, where we got to feature our experiments a couple of days ago:

Have you ever wondered what happens when you put a 13-m-diameter swimming pool on a merry-go-round? Probably not. But I am here to tell you today about what happens when you do just that, and what you can learn from doing so.

I am part of an international group of scientists, doing research on currents in the ocean (and you can read more about who we are and what you do on our blog: https://elindarelius.no). Specifically, we are interested in how warm water is transported towards an Antarctic ice shelf. As you can imagine, Antarctica is not the easiest place to travel to and measure the ocean, especially not during winter. There are some observations of warm water reaching the ice shelf and contributing to melting the ice, but it is not known yet under what conditions this happens.

Why a pool?
In order to understand how water behaves in the ocean, we are reproducing real-world features that we suspect have an important influence on the current’s behavior, but in miniature, and inside our water-filled tank. Then we can modify those features and observe which parts of them actually determine how the water flows, and which parts are not as important. In our case, we are changing the miniature coastline of Antarctica to see what makes the current turn and flow into a canyon instead of just going straight ahead.

Why rotation?
We need to rotate the tank to represent the Earth’s rotation. This is because the Earth’s rotation influences all large-scale movements on Earth, including ocean currents: Moving objects get deflected to their left on the Southern Hemisphere. Below is a short video of the rotating, empty tank, to show you what happens when you roll a ball in the rotating tank: It does not go straight ahead but just curves to the side!

[vimeo 233272527]

Before Nadine, the scientist shown in the video, climbed into the tank, you saw her walking alongside it. Even though the tank was turning very slowly (only one rotation per 50 seconds), she had to walk quite fast to keep up! This is how fast we need to spin the tank in order to have it rotate at the right speed for the size of our Antarctica.

How does it all work?
There is only one tank of this size — 13 meter diameter! — in the world, and it is situated in Grenoble, France. Researchers from all over the world travel to France to do their experiments in this tank for a couple of weeks each. In the gif below, you see the tank rotating: First, you see an office moving past you (yes, there are several floors above the water, including the first one with an office, computers, desks, chairs and all! That’s where we are during experiments, rotating with the tank) and then you can see the water below, lit in bright green.

There is a huge amount of effort and money going into running research facilities like this, and everybody working with the tank needs to be highly specialized in their training.

What do experiments look like?
When there is water in the tank, we need some special tricks to show how the water is actually moving inside the tank. This is done by seeding particles, tiny plastic beads, into the water and lighting them with a laser. Then special cameras take pictures of the particles and using complicated calculations, we can figure out exactly how the currents are moving. Below, you see a gif of one of our experiments: The current starts coming in from the right side of the image, flowing along our model Antarctica, and then some of it turns into the canyon, while most of it just goes straight ahead.

Depending on the shape of our Antarctica, sometimes all the water turns into the canyon, or sometimes all of it goes straight ahead.

What have we learned?
That’s a difficult question! We are still in the middle of doing our experiments, and the tricky part with research is that doing the experiments (even though that can be a huge undertaking as you see when you look at what a huge structure our tank is, or what enormous effort it requires to go to Antarctica with a research ship) is only a tiny step in the whole process. Nadine, who you saw in the movie above, is one of several people who will work on the data we are currently gathering for the next four years! But even though we are not finished with our research, there are definitely things we have learned. For example, the length of Antarctica’s coast line that the current flows along before the canyon interrupts its flow is very important: The shorter it is, the larger the part of the current that turns into the canyon. How all our individual observations will fit together in a larger picture, however, will still take months and years of work to figure out.

Where can I learn more about this?
If you have any questions, we would love to hear from you! We are hosting an “Ask Me Anything” event on October 18th (link here: https://oceanama.com/hi-i-am-mirjam-we-are-investigating-ocean-currents-in-a-13-m-diameter-455228/ but you can also leave questions on our Facebook page: https://www.facebook.com/EDareliusAndTeam/ or directly on our blog: https://elindarelius.no)

Introducing: Tae-Wan Kim

Posted on by Mirjam Glessmer

Written by Tae-Wan Kim

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My name is Tae-Wan Kim and I’m a senior research scientist at the Korea Polar Research Institude, where I’m in charge of physical oceanography in Southern Ocean. My research interests center on (1) the ocean circulation in continental shelf of Antarctic coastal region and (2) heat and mass balance between ocean and ice shelves. I joined my institute in 2011 and participated 8 times Antarctic and Arctic surveies. In Amundsen Sea of West Antarctic, my field programme involved the measurement of hydrography and ocean circulation using the shipboard CTD, ADCP and long-term ocean moorings. Espacially, I measured ocean current, temperature and salinity more than 2 years in front of Ice Shelf. From this data, we can identify the variability of ocean circulation and heat and mass balance between ocean and ice shelf. When I am in Grenoble, I want to improve my understanding on the ocean circulation process in continental shelf. This experiments using the coriolis platform will give a good chance for me!

Introducing: Adrian Jenkins

Posted on by Mirjam Glessmer

My name is Adrian and I’m a senior research scientist at the British Antarctic Survey, where I study the interactions between the ice sheet and the ocean that surrounds it.  The particular focus of my research are the physical processes that control the rate at which the ice melts into the ocean waters and the impact that has on both the ice sheet and the ocean.

I joined BAS in 1985 as a glaciologist with a background in physics and geophysics and initially undertook three seasons of fieldwork on Ronne Ice Shelf, a vast body of floating ice covering an area equal to that of France.  My field programme involved a long over-ice traverse, starting 800 km from the coast, where the 2-km-thick ice first goes afloat, and finishing at the front of the ice shelf, where the now 200-m-thick ice breaks off to form icebergs.  The thinning of the ice during its progress toward the calving front results from a combination of ice flow, as it spreads out over the surface of the ocean (much like a drop of oil would, only very much slower), and melting from the ice shelf base, where it is in contact with the underlying seawater.  Using a series of glaciological measurements that I made at regular intervals along the traverse, I estimated the rates of melting and freezing that must be occurring at the ice shelf base, then developed a simple numerical model of the ocean circulation beneath the ice shelf to explain those results. The problem of ice‐ocean interactions has remained the primary focus of my research efforts throughout my career.

In recent years I have been mainly concerned with the study of how ocean-driven melting of the much smaller ice shelves of the south-east Pacific sector of West Antarctica is controlling the rate at which ice is being lost from that part of the ice sheet.  The resulting thinning of inland ice there currently represents Antarctica’s main contribution to sea level rise, so understanding the processes that drive it is crucial for making reliable estimates of how much further sea levels will rise in the future.  I’ve used numerical models of the ocean and sent Autonomous Submarines beneath the ice to study the ocean circulation that carries warm water to the ice and takes meltwater away.  These studies point to the need to understand better the complexities of the ocean circulation near the front of the ice shelf.  The currents that cross the ice front determine how much heat is available to melt ice from the ice shelf base, but are difficult to observe.  That’s why I’m interested in these laboratory experiments.  With the geometry of the tank, its rotation rate, and the forcing on the circulation precisely known, we can begin to understand the fundamental controls on the cross-ice-front circulation.

Looking at our current’s structure over depth

Posted on by Mirjam Glessmer

For our scientific analyses, we look at the flow field at several discrete levels throughout the water depth. But we can — just for fun! — look at them almost continuously while the scanner is moving up and down, and that’s what I want to show you today. Isn’t it cool how the flow is so barotropic even though there are so many eddies and other things going on?

What happens when you accidentally change the rotation rate of the tank just a liiiittle bit? Inertial oscillations!

Posted on by Mirjam Glessmer

At some point the angular velocity of our tank was accidentally changed a tiny little bit. That was almost instantly corrected, however we could see the effect for quite some time later: inertial oscillations! All the water in the tank moved in circular motions at half the period of rotation.

You read about inertial oscillations in oceanography all the time, but it was really cool to actually observe them!

Elin receives award for polar sciences!

Posted on by Mirjam Glessmer

I’m sure there will be an official press release some time later today, and we will link to it when it comes out, but I thought I should let you all know that yesterday, on Nansen’s Birthday, Elin received the 2017 award for polar research of the Framkomitee.

I don’t know what was said in the official laudation or why Elin was chosen, but here are a couple of things I would have said that are more than enough to make her deserve this award more than anybody else I can think of:

That Elin’s research is outstanding doesn’t need to be mentioned specifically, otherwise she would not even have been nominated for a price like this one. When, some time last year, I read the proposal that ultimately funded all our time in Grenoble, doing research on this really cool pool-on-a-merry-go-round, I was so impressed by how all-embracing it was. In contrast to almost everybody else I know, Elin is not a one trick pony. It’s not enough for her to “just go on a research cruise and measure things” (and let me be clear: That in itself is an amazing trick that any pony, and any oceanographer for that matter, should be happy to master!), or “just do tank experiments”. Elin’s research combines sea-going oceanography, experimental work, and numerical models, and not just on paper as is sometimes the case in interdisciplinary research projects, but in practice. She sees how integrating results from one method with results from another will benefit both, and how adding a third could contribute even more. Of course she doesn’t do it all by herself; there is a reason this blog is called “Elin & team’s scientific adventures”. But the way she brings together people from different countries, with different backgrounds both scientifically and culturally, makes her team both stronger scientifically and so much more fun to work in.

Elin is also very invested in sharing her science and her excitement for it with the world. She has been blogging for years (find links to her previous adventures here) for different audiences: Primary school kids, teachers (even including teaching materials like experiments and exercises), the general public. And she gave me completely free reign over what would be published on this blog: We explicitly agreed to share all our “oh sh**, we should have thought about this before!” and “ooooops, that didn’t work!” moments with the world, in order to portrait science in a realistic way and maybe help others who might be struggling with their research by showing that it is normal to spend the first week or more at a new research facility just trouble-shooting (remember our persistent problems with the source, for example? Yes, that is the kind of stuff that doesn’t usually get shared in scientific publications or presentations, but isn’t it nice to know that other people’s research isn’t always going smoothly, either? Not even award-winning people’s research! And let me tell you, when I told other researcher friends about our plans to share this kind of stories with the world, they almost all declared us mad!). I believe these stories need to be shared (and there is actually research backing up this claim), but it takes a very strong person, like Elin, to actually do it!

But in addition to being an amazing researcher and science communicator, Elin is so much more. She is an inspiration and a role model. She makes doing exciting and complex research look easy. Not easy in a “oh, anyone could do it!” way, but in a “despite working really hard, she manages to have a life outside of work that seems to feed her energy levels, provide new ideas, sustains friendships, and ultimately makes her an even better scientist. Maybe I should try that, too?” kind of way. Elin is the kind of person who organises funding and then logistics for an early-career women workshop and then invites more than a dozen of those into her holiday house over night when, on the day of the event, the weather is so bad that we can’t take the cable car up the mountain to go to the place we had planned. Or that urges us to rent bikes in Grenoble and take the scenic route home to enjoy the views of the river and the mountain to recharge after a long and exhausting day in the lab. Or that cooks for her team in Grenoble, taking into account everybody’s different dietary restrictions. And — extremely impressive — Elin didn’t even complain when her phone drowned in her backpack (and not even in Bergen, in Grenoble!), let alone let us see the enormous strain she must have been under when experiments didn’t work out right away and we hadn’t found all the fixes yet! Long story short: Working with Elin means being reminded every day of why I love oceanography, and what a great and rewarding way of spending your time it is to work on exploring and understanding — and sharing with the world! — the wonders and puzzles of the ocean.

There would be so much more to be said about Elin and why I am so happy she got this award, but I have a day job that doesn’t involve writing laudation speeches, so this will have to do for now.

If you want to know what it was like to shake the Norwegian King’s hand (and I don’t even know if that happened, but I hope for his sake that he didn’t miss out on the opportunity to get to know Elin!) and all the other fun events of the day, maybe, if you ask nicely, Elin will tell you herself later. For now, join me in congratulating her! I can’t think of anyone more deserving for this award. Congratulations, Elin!!!

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Picture by Nils Gunnar Kvamstø, via Twitter

Introducing: Ho Kyung Ha

Posted on by Mirjam Glessmer

Written by Ho Kyung Ha

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Ho Kyung Ha is an assistant professor at the Department of Ocean Sciences, Inha University, Korea. His research interests center on (1) the ocean circulation and (2) associated particle transport in water column. Research has included the study of such diverse areas as rivers, estuaries, continental shelf, and Polar Oceans.

Using the long-term mooring system, he is seeking to understand the ocean circulation and hydrographic features. Most recently, he has studied the intrusion of warm water masses, which might be a potential heat deliver to under-ice system in the Arctic and Antarctica. He is analyzing the moored time series data in the view of the teleconnection of climate change signals between low latitude and Polar Oceans. In the field of particle transport, he has developed an acoustic inversion method to estimate the concentration of suspended materials and the flux. The developed acoustic techniques and approaches are being applied to the biology to monitor the transport of organic matters and migration of zooplankton in water column.