## Antarctica day!

December first is not only the day when you are supposed to change the batteries in the fire alarms (did you?) – it is also Antarctica day! To celebrate that I asked Nadine and Kjersti to send me their favorite photos from Antarctica – so please enjoy!

I managed to get my favorite icebergs down to these two…

Photo: E. Darelius                                                                                                                                                                         Photo: E. Darelius

… but it was just impossible to chose between the penguins – so here’s a bunch of them!

Photo: E. Darelius

Photo: E. Darelius

Photo: E. Darelius

Photo: E. Darelius

Photo: E. Darelius

Photo: E. Darelius

Photo: E. Darelius

Photo: E. Darelius

Photo: E. Darelius

… just had to add this one to show that they are not always cute!

## My students report: Rossby waves in a tank

I asked my students to write a “blog version” of the lab report they had to hand in as part of the course in geophysical fluid dynamics that I’m teaching this semester – below is one of them!

Planetary Rossby Waves (Written by Sigrid Vildskog & Guillaume Bonduelle)

When most people think about waves, they probably think of ocean waves crashing into the shoreline and beaches, but waves are so much more than that! In this report we are going to look at planetary Rossby waves, and how we can simulate them in the classroom.

First; what is a Rossby wave? Rossby waves are slow-moving large-scale waves that occur in rotating fluids, such as both the atmosphere and ocean. They are always propagating towards the west, due to something called vorticity and the change in the Coriolis force with latitude. The vorticity makes the fluid turn clockwise (or anti-clockwise) if it is displaced northward (or southward).

Second; what is Coriolis? Coriolis is the force that occurs when we are in a rotating system.  Large-scale movement on the earth is affected by the rotation of the earth. The effect of the rotation is dependent on latitude; there is no Coriolis force at the equator, and it increases towards the poles (negative values in the southern hemisphere).

Third: How do we simulate this change in latitude in the laboratory? In the laboratory, we use rotating tables, but the rotation rate of the table (and therefore the Coriolis force) is constant, so it’s impossible to simulate any kind of latitude. Lucky for us, there are two kinds of Rossby waves: one that is dependent on changes in latitude, and one that’s dependent on changes in depth. If we look at the equation describing vorticity, we see that changes in the Coriolis parameter (i.e. latitude), and changes in depth have the same effect on the vorticity. Therefore, in our experiment, we can use a tank with a slanted bottom to simulate the planetary Rossby waves.

Our rotating table is rotating anti-clockwise, so the shallow end of the tank is “north”. We placed a dyed ice cube in the north-east corner of the tank. The cold and heavy colored water from the melting ice cube sank towards the bottom and drained down the slope of the bottom of the tank. This movement induces stretching of the colored water column, and it will start to rotate. The rotation sets up a wave, that propagates westward in the tank. The ice cube itself moves to the western side of the tank with the wave!

This experiment allowed us to see the similarities between Rossby waves and Topographic waves with our own eyes, and experience that oceanographers can simulate a large scale system with simple equipment in a small laboratory.

## Full panic. Again.

– Are you sitting down? Anna is on the phone from Gothenburg.

– Yes? Why? The potential-catastrophic-scenarios-creating-center (pCCCC) of mine is normally working hard 24/7, but this time it was caught completely off guard…

– I just got a phone call from a truck driver on his way to deliver scientific instrumentation to me from Germany; and the only instrumentation I have in Germany is the one that is supposed to go with you on Polarstern.

You might remember that we had major trouble getting Anna’s instrumentation (that I’m to deploy in the Weddell sea this winter) through customs in Germany (if not, read about it here). Well, despite all our efforts (and prayers) and German documents we failed. To get the instrumentation onto Polarstern we would have to send everything back to Sweden and start over, we were told… and then we would have missed the deadline. Luckily Hartmut (the cruise leader) entered the scene and saved the situation by kindly “adopting” our packages onto his freight lists (don’t tell anyone!) and the problem that seemed impossible to solve was suddenly solved.

But now it seemed like Anna’s boxes had been returned to Sweden after all? What had gone wrong? What should we do? Would there be time enough to do anything? When was Polarstern leaving?

Anna’s desperate attempts to get the truck driver to turn around and return to AWI and Germany obviously didn’t work out…

At AWI they claimed that Anna’s boxes were still there. Maybe some of the boxes that had been unloaded from Mosaic had been sent to her by mistake?

My pCCCC wasn’t fully satisfied with that explanation… but that’s likely what had happened. Puh!

– or like a friend of mine used to say: “Another good worry wasted!”

## Deutsch, bitte!

Aaaah… full panic! It is three o’clock on a Friday afternoon. All the cargo that is being sent to me from Sweden to Polarstern is missing some mysterious export declaration number, it is stuck in customs and can’t be loaded it until the right number is on the right document. Sven, an extremely helpful technician at Gothenburg’s University is in contact with a German company that hopefully can help us obtain the missing numbers…  all of a sudden I get an e-mail from him saying that they need a detailed description of all the goods and its intended usage – in German. Now. I did two years of German back in high school – and I’ve brushed it off a bit lately with Duolingo since I know I’ll spend most of the winter on a German ship… But I’m not quite at the point where I can describe oceanographic instrumentation on the fly. I start with google translate – while desperately calling everyone I know who speaks German. No Nadine, No Mirjam… but Stefanie finally saves my day and makes sure that the text that google translate has produced isn’t just garbage. The document is on its way through cyberspace to the German company – and I’m back to correcting my student’s lab reports. Luckily, they are not in German!

My five pallets with equipment for this winters expedition to the Weddell Sea is now finally on their way to Bremerhafen & Polarstern! Many thanks to Helge and Algot for helping me packing and preparing – and to Tor for taking over when they ran away with Ilker to the Barents Sea, leaving me to finish up all the paper work – freight lists and proforma invoices are luckily not part of my standard vocabulary, but during the last couple pf weeks it feels like I’ve been doing nothing but that… and I’ve definitely learnt more about dangerous goods and codes like UN9031* and LQ** than I ever wanted to know! I do appreciate that Helge & Algot are back ashore!

*Li-batteries contained in equipment

*Low quantitity

## Stefanie’s current!

Although the Ocean still holds many secrets, it’s not very often nowadays that oceanographers discover new currents – but earlier this week one could read in NatureCommunications (and on nrk.no, in Norwegian) that scientists have drawn a new arrow on the map showing current systems in the North Sea! The “new” current brings dense water eastward along the Greenland-Scotland ridge from Iceland towards the Faroe Bank Channel, through which the dense water continues southwards into the North Atlantic.

I was very excited (and admittedly a litte bit proud!) to read about the discovery – since the paper is written by Stefanie Semper – the very first Master’s student that I supervised on my own. Stefanie has just submitted her PhD-thesis here at UiB, and I’m certain she will continue her great scientific work and that I’ll have the pleasure to read about her findings in the future!

The name of the current? Well, it’s not officially “Stefanie’s current” (although I’ll think of it as that) , but the slightly more descriptive (although boring) “the Iceland-Faroe Slope Jet”.

## Science is a team sport

The upside of the pandemic is that a lot of interesting meetings and presentations are streamed and recorded so that one can “shop around” and participate & listen without worrying about neither time zones nor CO2 and travel budgets.

Last night I had the pleasure to listen to Fiamma Straneo’s lecture “Ahoy captain, is that a glacier up ahead? Lessons learnt from working in Greenland’s marine margin” which is part of the International Glaciological Society Global Seminar Series (freely available here). I write “listen”, since the children’s drawers were empty and I had to do laundry at the same time – so I probably missed out on a lot of nice graphics and photos from the Greenlandic fjords that she was talking about… but I did not miss out on her conclusions:

Fiamma, who is a physical oceanographer working at Scripps while holding a Prof II position at UiB, and who is very much a team-player herself, used examples from her own research – from multi-disciplinary field campaigns in remote fjord arms to the (equally) multi-disciplinary and diverse team that stands behind the ISMIP6 projections –  to support her conclusions, and she did so very convincingly. Science is indeed a team sport!

## Welcome to GFI, Mari!

Yesterday Mari Myksvoll visited me and the oceanography group at GFI and we had a nice chat about fjords, oceanography, and everything in between! We are lucky to get to see Mari more regularly in the hallways from now on, as she soon will be joining us (20%) as an Associate Professor II. The paperwork is not yet in order, but the university administration better hurry up since the plan is that she will be teaching GEOF337, the master’s course in fjord oceanography, next semester. With her background in fjord and coastal modelling – and with her enthusiastic smile – I’m sure she will do a great job! And I will for sure enjoy to have another female*, fjord-interested oceanographer around! Welcome to GFI, Mari!

* number three in the teaching staff

## Hipp Hipp Hurray!

Corona is turning our lives up side down – but that’s no reason not to stand up and sing “Happy Birthday” to Prof. Emiritus Arne Foldvik who turns 90 years old today! (Those of you who read Norwegian can read about him here)

Arne started out his scientific carrier as a meteorologist, studying among other things the waves that are generated when wind blows over topography  (he did that using the long tank down in the basement of GFI where I’ve taken my students to play with Nansen’s dead water) – but he later turned to oceanography.  Around the time when I was born he led his first Norwegian oceanographic expedition to Antarctica and the southern Weddell Sea. During that expedition he found what the Americans had failed to find a few years later: The Filchner overflow, an enormous* under water river that carries cold and dense water from the Filchner-Ronne ice shelf cavity to the bottom of the Weddell Sea. This discovery is one of the reasons I’m working with polar oceanography today, as I spent the three years of my PhD revisiting the exciting data that Arne & co had collected in the outflow.

The last time Arne came by my office, we chatted about towed icebergs, melting ice and the experiment I did in my “Nansen’s memorial lecture” (which Arne attended). Arne has been involved in projects where the aim has been to tow icebergs from Antarctica to dry areas in demand of freshwater (originally the middle east, and just a few years ago, to South Africa ). Arne told me, that if one did that, one would get ice into water warm enough, that the results of my experiments would no longer hold.

The density of seawater is a non-linear function of temperature and salinity, and while salinity dictates the density for cold water (causing the lines of constant density to be almost vertical in the TS-diagram below), temperature is more important for warm water (causing the lines of constant density to tilt more). So, that means that while the (fresher and colder) melt water mixture is lighter than the ambient water if it is cold, it will actually be denser if the ambient water is warm enough! Off course we had to try this out – I never got around to doing so, but yesterday, Mirjam finally did!

Somewhat disappointing – we realized that the result is more or less the same, independent of the water temperature. Does that mean the physics (and Arne) are wrong??? Probably not, it probably just means that the molecular diffusion of heat is acting fast enough that the “cold” melt water mixture doesn’t stay cold enough to sink 🙁

Anyway, here’s a stratified toast to Arne Foldvik!  HAPPY BIRTHDAY!

* 1.6 million cubic meters per second – that is almost ten times the Amazon river

## Moviestar for a day?!

A while ago I was asked by the university (#realfaguib) if I wanted to present myself and my work in a short movie that they want to show to future students – and a few days later I found my office occupied by cameras of different sizes and three very nice journalists/moviemakers/photographers that came along. I quickly realized that making a short movie – I think they only want a minute or two – takes a loong time! Repeat, repeat, repeat – look into the camera, walk faster, walk slower, one more time, slower, shorter, clearer, louder, start over, look that way, look here, smile, don’t smile… at the end of the day, I was quite happy that I’m not a Hollywood movie star but an oceanographer in Bergen

I think the movie will be released  shortly – but until then you can enjoy the nice article they wrote to go with it (in Norwegian)