05/01/2018 We are on the way to the Amundsen Sea

Guest blog by Karen Assman

After leaving Gothenburg on 12 December in the snow, I spent a warm day exploring and eating my way through Singapore on the way to Christchurch, New Zealand and then a few days getting over the jetlag in New Zealand summer. On 17 December it was time to return to Christchurch and meet up with Johan, the technician who is helping me with the moorings on the cruise. We spent the next day shopping for a few bits of equipment that had appeared on the list after the container had left for New Zealand in early October. If anybody should require a chandlery or hardware store in Christchurch I can probably point them into the right direction. On 19 December we went to the port in Lyttelton and said hello to Araon who had come into port. Almost all our equipment was on the quayside next to the ship – apart from the mooring anchors that should have been delivered from Wellington that day. The agent assured us that they were probably on their way and we went off to buy last minute supplies like snacks and flour for the bread maker etc.

Pre-cruise summer in New Zealand: The Banks Peninsula near Christchurch.

Loading the equipment that was on the quayside and finding space for it on board went very smoothly the next day and we were finished by lunchtime. But still no mooring anchors. A phone call to the very helpful technician at the New Zealand Institute for Water and Atmospheric Research (NIWA) who had organized the anchor weights for us told us that the weights were still in Wellington. She managed to impress on the freight company that the anchor weights needed to be with us in Lyttelton the next day and things started to finally move on the tracker app.


We were scheduled to leave on 21 December at 14.00 and after delivering the rental car back to the airport in the morning, Johan and I took a taxi to Araon. At 11.00 the tracker app told me that the anchor weights had made it to the Christchurch depot of the freight company. A phone call to check when they were being delivered turned out be rather essential after it turned out they weren’t to be delivered until the next day. After the phone call they were practically on their way and did make it just in time. The first mooring line for the ship was let go as soon as the last weight touched the deck. And we were on our way!

The mooring anchors on the helicopter deck of Araon. Note the linesmen on the quayside waiting to let go the mooring lines.

So why were we so anxious about 5 tons of old train wheels? The driver delivering the weights did wonder, as might you. Are you going to sink them? Essentially that is what we are going to do. The strings of moored instruments that we are going to deploy have buoys to hold them upright in the water column and to give us data at different depths and so they need something heavy at the bottom to anchor them to the same spot, until we come back two years or so later to release them.

The moment just before dropping the mooring anchor. Photo from a deployment on the 2015/16 Araon cruise to the Amundsen Sea.

The Amundsen Sea is a long way from anywhere – part of the reason why it remained unexplored until relatively recently. Our first mooring was scheduled for day 16 of the cruise and we settled into life on board, doing bits of preparation, other work, going to the gym, meeting our shipmates for the cruise and getting the on-board bakery, i.e., the bread maker going. A Christmas tree appeared in the hallway and we had a party on Christmas Eve to mark the occasion. Sea and weather were kind to us, so the sailing was smooth and it felt more like a cruise to the sub-tropics. This was partly due to the fact that the ship was going east to the Udintsev Fracture Zone to retrieve three moorings that had been deployed there on the last cuise and to do a hydrographic survey. Fracture zones are gaps in the sub-sea ridges that run across the abyssal planes of the world oceans. The Udintsev Fracture Zone steers the Antarctic Circumpolar Current that encircles the Antarctic continent southward and is thought to be one of the reasons why warmer water reaches the ice shelves in the Amundsen and Bellingshausen Seas. After recovering two of three moorings and shaking out a few teething problems in the sampling equipment on board, we started to head south towards the Amundsen Sea and as it started to snow things were looking distinctly more polar.

The Christmas tree in the corridor on the main deck. Note for next year: Always tie your Christmas tree to something so it doesn’t fall over in high waves.

Live (but delayed) reports from Araon and the Amundsen Sea!

Karen’s texts got stuck somewhere between the ship and Bergen…. but now they are here and I’ll share her reports with you! First some background…



Why are we going to the Amundsen Sea, who is going on the cruise and where is the Amundsen Sea anyway?

For a long time nobody went to the Amundsen Sea. James Cook turned around at 71° 10’ S in 1774 faced with thick multi-year sea ice and apart from one more attempt by the Belgica in the early 1900s, no ship went there until 1994. That cruise discovered that the bottom layer of water on the continental shelf was filled with warm (1-2 C) and salty water and this explained the high melt rates that glaciologists were seeing under the floating ice shelves that fringe the area. Interest really rose when the glaciologists realized that the area had the highest thinning rates on the Antarctic Ice Sheet. Since the atmosphere in Antarctica is generally too cold to cause much melting at the surface of the ice sheet, the warm ocean layer and the high melt rates in the ice shelf cavities was identified as the culprit. So for the last 15 years there have been regular scientific cruises to the Amundsen Sea to find out what controls the flow of the warm water and how and why it may have changed to cause the observed thinning of the ice shelves.

Our cruise is part of this effort. We are on the South Korean Research Ice Breaker Araon that is owned by the Korea Polar Research Institute KOPRI. Two years ago we went to the Amundsen Sea to Araon to deploy an array of moored instruments to measure the flow, thickness and temperature of the warm water layer. One of these sites has had oceanographic instruments for 8 years, the others have never had any instruments before. Hopefully all of our so-called moorings will have measured temperature, salinity, oxygen and current velocities over the past two years and will come back in one piece when we release them.

My name is Karen and I work as a researcher at the Department of Marine Sciences at the University of Gothenburg. I have done research in the Antarctic seas and how they interact with the sea ice and ice shelves since my PhD. Then I was mainly using numerical models, now I am mainly working with observations. I was on the Araon cruise two years ago when we put the moorings into the water that we are now recovering. I have started crossing my fingers that they all come back and am really excited to start looking at the data. On board Araon I also run the bread maker a.k.a. the on-board bakery – Korean breakfast isn’t for everybody!

Johan Rolandsson works as a marine technician with MMT (Marine Measurement Technology) in Gothenburg. He went on the Araon cruise in 2014 and will help me with the mooring recoveries and deployments.

Karen on the last Araon cruise to the Amundsen Sea.


The initial cruise track and stations (courtesy of TaeWan Kim).

The South Korean research ice breaker Araon in her natural element on the 2015/16 cruise.

Johan waiting for a mooring to appear on deck.


Mooring recovery in the Amundsen Sea!

I’m spending the austral summer at home in Bergen for a change – but luckily I’ve got People Down South helping me out! Karen Assmann & Johan Rolandsson from the University of Gothenburg is onboard the Korean Icebreaker Araon in the Amundsen Sea, and these days she’s busy recovering moorings with oceanographic instrumentation that we deployed during a cruise in 2016. During the weekend (while I was out skiing) I received message after message: one more mooring on board!

For now three of my moorings are recovered, meaning two years of data on the flow of water towards and away from the western most front of Getz ice shelf. Until now there were no data at all from this region during Winter!

There is still one more mooring to go – but there is a lot of sea ice around, so not sure they’ll be able to pick it up this time around. Finger’s crossed!

You can see where Araon is if you click here!

Mooring deployment in the Amundsen Sea in 2016. I’m about to say “Good bye” to one of my microcats, an instrument that measures temperature, salinity and pressure. Now it is safe back on deck again and it will Return to Bergen in a couple of months.

I’ll let you know what happens and hopefully get Karen to send some photos – but for now, I just want to say “Thank you Karen and Johan, well done – and thank you Hoon and KOPRI for letting us join your cruise!”

Mesmerizing flow patterns and sad goodbyes

Written by Anna Wåhlin

It is the final day of experiments here at the Coriolis platform. The apartment is emptied of personal belongings, bicycles are being returned, goodbyes are stretched out. The lasers will soon be dark, the platform will grind to a halt and the tank will be emptied. It has been a fantastic time! I am amazed at what we have accomplished together during these weeks – answers to some of the most basic questions that are currently asked about the future for the Antarctic ice sheet.

Figure 2a-d: More mesmerizing flow patterns

The last days have been spent re-running some of the experiments that needed an extra quality-check, and we finished the very last one only an hour ago. Next week I will stay behind alone to try to get some nice photographs of the flow for our future publications. In order to prepare for that we were testing some different dyes. Red dye absorbs the light of the laser efficiently and gives a dark shadow on the images. Our all time favorite is Rhodamin – it is a fluorescent dye that produces its own light if you shine on it with green laser. We spent a good hour simply staring at the eddies and flow, mesmerized by the motion and flowing patterns. A very fine ending to the week! And a suitable finale to the time we have spent here on the rotating platform.

Video: Visualization of a beautiful barotropic eddy created outside the channel. It stayed like this for a good hour. You can see the barotropic structure since it moves in unison on the surface and below the surface, in a nearly perfect two-dimensional motion.

Introducing: Thomas Valran and Samuel Viboud

We have presented all the scientists that are involved in the project, but still haven’t introduced the two most important people: Samuel and Thomas without whom we would not have been able to conduct the experiments.

Today, part 2: Samuel Viboud, for Thomas see here.

Samuel is an engineer in experimental techniques on large instruments and has been working at LEGI since 2001, when it was still at another place in Grenoble where Elin, Anna and Adrian conducted experiments about 10 years ago. To be in charge of the rebuild of the Coriolis platform was the most exciting event for him. Samuel is the technical director of the Coriolis platform and the head of the mechanical department at LEGI. Thanks to his creativity, technical know-how and sense for innovation, he received the well-deserved “Médailles de cristal” from CRNS in 2015.
About his personal life he says:
“Coming from a winemaker family who cultivates the grape varietal: “Mondeuse”, I live in the village of Apremont in Savoie, and do not hesitate to spend my time with work such as harvesting and bottling. In my personal life that I share with my wife and my 2 children, the exchange, the attention and the mutual support are daily. Concerning leisure, I am passionate about sport and particularly about road cycling. I regularly climb the mountain passes of the region and commute 100km to work by bike. The mountains are also my playground especially in winter, with ski touring that I like to share with my friends. What characterizes me in the end in life as at work are the essential values such as: sharing, conviviality and family.”



Introducing: Thomas Valran and Samuel Viboud

We have presented all the scientists that are involved in the project, but still haven’t introduced the two most important people: Samuel and Thomas without whom we would not have been able to conduct the experiments.

Today, part 1: Thomas Valran.
Part 2 to follow on Monday

Thomas is an engineer at the Coriolis platform and has been working for LEGI since March 2016. During his diploma in industrial engineering at the “Ecole nationale supérieure des Mines de Saint-Etienne” he worked as apprentice engineer for Schneider Electric. At the Coriolis platform, the most exciting part for him is to work for many different projects that never make the job boring. Due to his experience in climbing he moves on the supports of the platform very gently despite the high rotation speed. In his spare time, Thomas likes to go on road trips with his motorcycle or help at his parent’s farm where he grew up and where there are about 100 cows to take care of.

We discovered a new galaxy! Or at least a very pretty vortex

When we move our wall back and forth, we create very strong wing tip vortices that persist for quite a long time.

Above, you see the vortex, lit by a laser sheet close to the surface. You can see the whole column rotating as one, that bright smudge below the swirl is the lower part of the column. There are so many of our neutrally buoyant particles in there that the column looks bright even though it isn’t directly lit by the laser.

And in the picture above, you see those bright smudges on the left of the picture? That’s particles that the vortex hoovered up and then dumped in its path, pretty much like a hurricane would.

And that’s what it looks like as a gif:

How salt changes the current

Until the beginning of the week we had only conducted barotropic experiments. This means that we induced fresh water into fresh water. How boring, you may thing… Well, although these experiments were very interesting, you are probably right because this setup doesn’t quite correspond to reality. At the coast of Antarctica, dense water is on one side produced by the growth of sea ice and on the other side origins from deep water that spills over the coast onto the continental shelf. Because the continental shelf slopes down towards the ice shelf, the dense water reaches towards the ice shelf. Our aim is to find out how the water behaves as it reaches the ice shelf front.

To reproduce this dense water flow, we inject salt enriched water into the channel. This relatively dense water approaches the ice shelf front along the left channel slope. To see a clear boundary between the dense and the fresh water, only a density difference of 1 kg/m3 is needed. The density difference increases the velocity of the current a lot, so that the experiments last much shorter. While the barotropic current was mainly blocked by the ice shelf front, the baroclinic current can freely enter the cavity beneath the ice shelf, as the dense water is largely decoupled from the freshwater. Because the fresh water layer above the dense current is barotropic, the previous experiments were of big interest as well to see how the upper layer behaves as the current reaches the ice shelf front.

On the cross section through the channel, the dense water separates clearly from the freshwater. It flows parallel to the slope to its left. Because we built a wall at the end of the channel (see our previous post: https://skolelab.uib.no/blogg/darelius/2017/10/20/closing-off-our-channel-at-the-ice-shelf-end-to-avoid-unrealistic-outflow/), the channel fills up quickly with salt water, which we have to evacuate after each experiment.

The dense, saline water contains many particles and gets visible in the vertical laser sheet. It flows towards the ice shelf (=towards us) along the slope to its left side.

In the photo of the cross section, you can also see 4 probes sticking in the water that we use to measure the density close to the source and close to the ice shelf front. We can then calculate the velocity of the dense current and the mixing between the fresh water and dense water along the channel.

In this experiment, we injected a flow that is 1kg/m3 denser than the ambient water. During the scans, the vertical laser shows the position of the dense current and the 4 probes (2 in front of the ice shelf front, 2 in front of the vertical laser) measure the change in density with time.

Introducing: JB Sallée

Written by JB Sallée
JB Sallée is an oceanographer interested in the dynamics of the ocean and climate with active research efforts on the study of the Southern Ocean and Antarctica shelf circulation. His research mostly focuses on the observational connection between the ocean surface and the deep ocean interior, with particular emphasises ocean ice-sheet interaction as well as on heat, salt and anthropogenic carbon sequestration in the Southern Ocean. His research tackles questions from oceanic turbulence to large-scale ocean circulation, as well as on the impact of ocean physics on biology.

“No one believes a theory, except the theorist. Everyone believes an experiment — except the experimenter.”

Different types of experiments, and why we use such a weirdly-shaped “Antarctica” and are happy with it.

When we want to show people images of our model experiments in a tank, people often imagine that they will be shown cute little miniature landscapes, looking much like the ones you see for really fancy model train setups. And then they are hugely disappointed when they see pictures like the one below and we tell them that yes! that’s our Antarctica that Nadine is climbing on, while Elin is sitting in the Southern Ocean.

The kind of experiment everybody hopes to see could, according to Faller (1981), be classified as a simulation: representing the natural world in miniature, including every detail. Data from those experiments — since they would in theory be realistic representations of the real world — could be used to fill in missing data from the real world in regions that are hard to get real data from, like for example the Southern Ocean. However, since those experiments are designed to represent the complexity of the real world, interpretation of the experiments is as complex as it is to interpret data from the real world: There are so many processes involved that it is hard to isolate effects of individual processes.

The kind of experiments we are doing would be classified as abstractions. Faller describes this kind of experiment as similar to abstract art: Only the main features, or better: the artist’s interpretation of the main features, are reproduced and everything else is omitted. That makes the art difficult to understand for anyone who isn’t well versed in abstract art, but for the experts it is obvious what the point is.

In case of our experiments that means that we have all the relevant features, or better: our interpretation of what we believe to be relevant features, of Antarctica present in the tank: the parts of topography that we think have an influence on how the current should behave, i.e. a V-shaped canyon, a source that supplies water of the correct properties into the ambient “ocean” water, an ice shelf. And when that ice shelf is tilted, we feel like our experiments are already becoming pretty realistic!

These abstractions are the kinds of experiments in which you can, because they are relatively simple, develop new theories when new features of the circulation emerge that you then have to rationalize and include in your theories after the fact.

We have actually also done another type of experiment, a verification. I wrote about it in this post: we tilted the ice shelf because this is a case for which we actually knew from theory how our current should behave, in contrast to all the previous experiments where we didn’t actually know what to expect, and we were happy when we observed exactly what we expected based on theoretical considerations. So in this case the experiment wasn’t about discovering something new, but rather making sure that our understanding of theory and what goes on in the tank actually match.

Faller describes a last type of experiment: the extension. That is the kind of experiment that you could perform after a successful verification experiment: Pushing the boundaries of the theory. Does it still hold if the current introduced in the tank is very fast or very slow? If the water is very deep? If the slope of the ice shelf is very large or small? Basically, every parameter could now be changed until we know for which cases the theory holds, and for which it does not.

So why am I writing all of this today? Faller’s (1981) article, before he goes on to describe the framework to think about geophysical fluid dynamics experiments that I mentioned above and which I find quite helpful to consider, starts with the sentence “No one believes a theory, except the theorist. Everyone believes an experiment — except the experimenter.” On this blog, our goal is to bring the two together and not make anyone believe either of them, but to show how both can work together to mutual benefit.

Faller, A. J. (1981). The origin and development of laboratory models and analogues of the ocean circulation. Evolution of Physical Oceanography, 462-479.