Postdoctoral Research Assistant in Ocean Modelling
University of Oxford Department of Physics (Atmospheric, Oceanic and Planetary Physics) Grade 7 (£30,434 – £37,394) Full time, fixed term, 32 months Closing date: 30 September 2015 Job reference: 119325
Applications are invited for a Postdoctoral Research Assistant in Ocean Modelling. This post is a UK contribution to the international “Overturning in the Subpolar North Atlantic Program” (OSNAP) and it is available for a fixed-term of 32 months.
The postholder will use a state-of-the-art ocean model and its adjoint to probe the sensitivity of the circulation of the subpolar North Atlantic to surface forcing anomalies and to anomalies observed by OSNAP in the ocean interior. The successful candidate will collaborate closely with OSNAP partners at Oxford, in the UK and internationally. The postholder will have the opportunity to teach.
Applicants should possess, or be very close to obtaining, a doctorate in a physical, mathematical or computational science. Strong numerical modelling skills and proven track record of original research is essential. Previous experience in physical oceanography or climate physics will be an advantage.
Only applications received before 12.00 midday on 30 September 2015 can be considered. You will be required to upload a CV, publication list, supporting statement and details of two referees as part of your online application. To apply, or for further details including the job description and selection criteria, please visit www.recruit.ox.ac.uk and search by vacancy number 119325.
As we are nearing the end of our cruise the last CTD station was finalized late last night, and as the weather is still as calm as we would never have expected it to be in the Irminger Sea, I take some time to reflect on our journey. It is always strangely discomforting to come close to the end of a period spent so intensely working with all folks on board and that one has got to know over the course of the trip. I wonder why that is. We can look back at a very successful cruise with all and even more done than was initially planned.. The OSNAP East mooring array in the Irminger Sea has been serviced, 51 CTD stations were taken and 34 floats were released in this part of the subpolar gyre. Everyone was working so well together and the high pressure over the Irminger Sea kept intense low pressures swirling well away from us such that it some times looked like.. the Mediterranean? I appreciate life on board as we can focus on work, and do not need to worry about other usual daily business or errands. In addition though the unexpected events make it certainly more fun, like an occasional Tuesday evening that turns into a fun party or a big group of killer whales passing by, or the surprising clear view of Greenland being still 60 nm away. I feel like by now we are well into the routine of working together, data handling, and organization that it feels odd to abandon all that now.. and that it suddenly comes to an end. I do realize most people are ready to get off the ship, particularly our dear colleagues from SAMS who had already been working on RV Pelagia for 3 weeks during leg 1. And surely the students who perhaps spend their first weeks ever at sea and probably are happy to go home and have a bit of summer holiday in a warmer place. Luckily due to the good weather we were ahead of schedule and could take some time to do a little bit of fishing on our way back in to port.. resulting in not too bad catches either.. Apart from being grateful to our science team, students and technicians, my big thanks for making this cruise successful go to all the hard working deck crew, engineers, captain and officers. It has been a real pleasure sailing with ya all.
My pleasure to join the OSNAP cruise on Pelagia, to meet kind friends from Europe and America who devote themselves to marine career, to experience series of interesting survey. Along with the days on sailing, it’s not only the difference in culture and tradition but also their passion on oceanology with heart that shocks me. In spite of the same survey to sail in Pacific, there seems to be something lost as pursued years ago, the curiosity to explore the uncertainty.
At occasional glimpse on the patience to ADCP of Dave, the worry about the calculation on Julian Days of Laura, the preciseness on CTD from Ruud and Karel, and the excitement with photo of Pluto buy tramadol online from NASA in Maarten, I can feel the deep charm of scientific spirit, which roots on the sweat spilled on the way to pursuit for truth. It cannot be measured with material things unless the Tao in Chinese tradition. Road is so long coming that I will seek to search with my will unbending.
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By Huang Lei on Pelagia
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Narrow words could be recognized as curved on the cloudy screen
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Slim letters spread with wind like mails
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Soft waves in the sunshine blinked
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All these would make no disturbance to my mind unless the northern breeze blew over my grey temples.
Welcome to Qingdao. Please email to me as you occasionally pass by Qingdao.
Since the start of the cruise I’ve been asked this question by many people on the ship. Possibly those of you on shore are wondering the same thing. Why do we deploy RAFOS if we already have current measurements from the moorings?
To try to explain this I’ve made two plots using data from a model run I’ve brought on my laptop. It’s a 15-year model time series that includes the Irminger Sea. The model grid point spacing is small (about 4 km) which is quite important for this example as the high resolution allows the model to simulate eddies. Eddies are rotating bodies of water that can hold on to their properties for a while. They are called cyclones and anti-cyclones based on their rotation (counterclockwise or clockwise). Basically they are similar to low and high pressure areas in the atmosphere, only smaller (in this region) and under water.
If you plot the mean velocity field (so averaged over the 15 years) the cyclones and anti-cyclones more or less average out and what remains is the mean current circulation. The mean velocity field for 500 m depth in the model is shown below.
The model’s mean flow. The colors indicate flow speed, from white (zero) to red (“fast” 50 cm/s). The arrows indicate direction as well as speed. The magenta line is the track of a “virtual RAFOS” launched in the mean flow. It starts at the magenta dot.
If you “deploy” a RAFOS on a fixed point in this flow field is will take the same path no matter at which time you deploy it because the flow field doesn’t change. This is what oceanographers in the early days expected to happen in the real ocean as well. Of course, they didn’t have the measurements we have now. The first current meters only counted the number of rotations the propeller made during the deployment. The oceanographer would get the speed by dividing the number of rotations by the time the instrument had been deployed. This gave them the mean speed, but no information about the variability of the flow field. They got the direction of the currents by sending down a compass filled with a liquid that would gradually set and fix the compass’ needle in place.
We know now that the ocean is highly variable and that the mean speed doesn’t give you the total picture. Consider the plot below. It shows the tracks of 12 virtual RAFOS floats deployed in the model field. This time we use the model field that changes every three days and we launch the floats each January 1st. The tracks in this figure show a very different picture than the magenta line before.
Tracks of 12 virtual RAFOS deployed at the same location as in the previous plot. For these deployments we used the time varying model flow field. Each RAFOS is launched on January 1st of consecutive years. The grey shading indicates where the model flow field is most variable.
Tracks of 12 virtual RAFOS deployed at the same location as in the previous plot. For these deployments we used the time varying model flow field. Each RAFOS is launched on January 1st of consecutive years. The grey shading indicates where the model flow field is most variable.
The RAFOS floats are swirled around by the eddies and each float takes a completely different path, even though they are launched at the same spot (just not at the same time). The much larger area covered by the floats on the eastern side of the basin is an indication that a lot of mixing between water masses may take place there. Also, these RAFOS (which covered one year in both plots) don’t quite get as far as the RAFOS released in the mean flow. It ended up at 60.6 ?N and 58.4 ?W, well outside of the plot. This matter because a parcel of water that starts out warm and travels through colder water will lose a lot more heat if it has to take a longer path to get somewhere.
In two years’ time the real RAFOS we deployed during this cruise will show us the actual underwater pathways. RAFOS deployed in 2014 and those that will be deployed in 2016 will show us how those pathways vary from year to year. Maybe it will look like the model. Maybe not…
It is been a week since we came back to dry land. After 35 days at sea, everyone was pretty excited to be back at home!
Looking back at what we achieved, the cruise is already a big success, as we managed to carry out all that was initially planned (and even more). It is now time to look more in detail at the data from the 131 CTD casts, the ADCP transects, and the 58 microstructure profiles. Some of the autonomous instruments we deployed during the cruise should (obviously) send observation for the next few years. A twin cruise should happen in 2017 to recover the 9 moorings we left at sea, and gather more in situ observations. Now it is time to start a new phase of the work, as it will probably take months (if not years), to dissect all the data and unravel all the physical processes we have capture in our the set of observations. This should allow us to provide a comprehensive description of the oceanic conditions in this region, and to better describe, quantify and understand all the complex oceanic features encompassed in the dataset.
At a time when we are all getting back to a more normal life, we also know that this experience at sea will remain in our mind for a long time.
As mentioned before, the recovery of the first moorings on this cruise was very successful: all but one instrument on the 5 Dutch moorings in the Irminger Current had recorded data for one whole year. The large data return of ocean temperature, salinity and velocity at 15 minutes to one hour intervals at selected depths between 100 m and 2900 m depth allows us to investigate the northward flowing Irminger Current. Earlier estimates were derived from summer data (shipboard data) only. Now we can quantify the total volume and heat transport of the Irminger Current based on these continuous measurements, address seasonality, and investigate variability in relation to e.g. atmospheric patterns. After retrieving our data, the instruments have been serviced, batteries replaced, and the moorings are deployed again on the Reykjanes Ridge – ready to collect another year of data. We are now working our way westward in the Irminger Sea and have reached the English moorings in the Deep Western Boundary Current, the cold and dense current flowing southward. Cross our fingers for another few days with good mooring recoveries!
Since we arrived at the moorings sites in the northward flowing Irminger Current on the Reykjanes Ridge, we have been working around the clock. With all 5 moorings recovered in two days, and needing to deploy those again soon, the days seemed too short and time flew by. We will show and tell more soon about these mooring recoveries (YES, with a lot of excellent data to work on for at least a little while). As we needed a couple of days to prepare our instruments again to redeploy the moorings for another year we did 20 full-depth CTD stations (so high ordertramadol resolution) whilst steaming back towards the start of the mooring line on the top of the ridge. This short video illustrates that…
Leg 2 will service 12 moorings: G: the Dutch moorings, D2: British moorings, C: German mooring, L: Dutch profiling mooring, and E1 and E3: RAFOS float deployments
After a bright sunny day of loading and getting ready on RV Pelagia in the port of Reykjavik, we are well underway to retrieve and redeploy 12 tall oceanic moorings in the Irminger Sea (marked with leg 2 in the red box). The successful team from leg 1 arrived in Reykjavik two days earlier than planned and they handed the ship over to us. The moorings we will be recovering have been collecting continuous measurements of temperature, salinity and currents in the Irminger Sea for a whole year. We expect to arrive to the first mooring site on the Reykjanes Ridge on Friday morning to start recovery and read the first data sets from the instruments. After that we head west to collect all 5 moorings on the Reykjanes Ridge and traverse back again whilst doing CTD measurements and float deployments on the ridge after which the moorings will be deployed again for another year.
The mooring data collected during this cruise contributes to both the OSNAP and NACLIM programs. We have an international team with 7 different nationalities. Some of us have to get used to being at sea while others appear to have no problem to focus on computer screens… the weather so far is great though we are expecting more wind and waves tomorrow.
On June 6, 2015, I embarked with the RREX team on R/V Thalassa for a five-week journey across the subpolar North Atlantic. The ultimate objective of the cruise is to fathom the mysteries of ocean flows near the Reykjanes Ridge, a submarine mountain chain connecting the southern tip of Iceland to the Mid-Atlantic Ridge further south. Though achieving this goal will remain a continuing challenge for the months and years to come, some distance has certainly been covered. A huge amount of information on local currents, turbulence and water properties has already been collected, and much more data is to be recovered from the vast array of autonomous instruments that have been deployed. Promisingly, preliminary (real time!) analysis of the data already shows some intriguing and unexpected features. The next step will be to build an understanding of the underlying physics by comparing the new data to historical observations, laboratory experiments and theory.
But for a student living its first embarkation, such a cruise holds many more lessons than those coming from the data itself. Now barely ten days away from the ship’s docking in Brest, let us venture a brief assessment.
Under glorious blue skies and with a fair tide running behind her the R/V Pelagia left the Port of Southampton, England on June 16th to officially begin the OSNAP field season of 2015. The two main science teams joining the cruise, from the Scottish Marine Institute (SAMS) led by Dr. Stuart Cunningham, and from the University of Miami led by Dr. Bill Johns, had been busy unpacking and preparing moored instruments at the National Oceanography Centre in Southampton for the previous several days in anticipation of the ships arrival. Also aboard are scientists from Woods Hole Oceanographic Institution and the Ocean University of China who will deploy a number of RAFOS floats and a glider along the OSNAP East line. After an efficient loading operation the ship was underway through the English Channel, around Lands End, and then northward through the Irish Sea to the first work area off the Scottish coast in Rockall Trough.
The planned cruise track of PE399. Red squares mark mooring locations to be recovered and redeployed; yellow dots represent CTD stations with lowered ADCP. The cruise departs from Southampton UK and ends in Reykjavik, Iceland.
