05 Jan - New Year, new crew
RRS James Clark Ross Diary
Noon Position: 51° 47.1 S, 57° 41.3 W)
Distance Travelled since Grimsby: 18627.5 Nautical Miles
Air temperature @ Noon today: 7.2°C
Sea temperature @ Noon today : 11.4°C
Weather: Good, South, 6/7, 988.2 mb
New year, new crew!
Four months since leaving Grimsby, the JCR crew were ready to go home. Captain Burgan's crew had completed their time at sea and were looking forward to getting back to Stanley and handing over to Captain Elliot's team. Having counted down the days for the last few weeks, made plans for what to do on leave and debated travel arrangements tirelessly, the end was in sight and home not too distant. First we had a few days of science to complete as we sailed back towards the Falklands across a very calm Drake Passage (see below). Once back at FIPASS in Stanley, everyone prepared their handover notes, cleared their cabins and awaited the next crew's arrival. On Saturday, 28 crew arrived and 25 scientists who are here for the forthcoming 'bioscience cruise' and after a brief hand over the old crew disappeared down the gangway as fast as they could drag their suitcases to the bright lights of Stanley.
However not everyone managed to jump ship and three lucky (or not! - Ed) souls stayed on board. John Summers who is the deck officer and has been onboard for several months, Jo Cox has decided she loves it so much she is staying on for another 6 weeks and I are remaining. It is sad to see our friends get off but it is good to see them so excited and happy about going home to make up for a Christmas and New Year away. It is weird to have your home suddenly invaded by 50 strangers. Home hasn't changed at all and the routine onboard is virtually identical but everywhere there are new faces. One has to learn all over again a new set of habits, who sits where in the bar and how people take their tea etc. Little things also change such as the layout of the menu each day and the type of bread baked. The new crew have fitted in seamlessly and immediately started their jobs with no major changes. There is a subtle reality shift and you know something has changed but can't quite put your finger on it. It is great to have a new set of fresh faces around but a pain having to introduce myself again to everyone. The king is dead, long live the king.......
The early bird sees a flasher!!
For most people 'Green Flash' are a pair of naff old tennis shoes from 20 years ago. However, this week we were lucky enough to witness a much more spectacular type of green flash. At sunset, the small segment of the upper part of the sun which is the last part to slip below the horizon may turn a bright emerald-green at the very instant of setting. It is seen as a bright green flash and once seen is never forgotten. The phenomenon only lasts for a fraction of a second and hence why it is described as green flash. The green flash is only rarely seen because the observing conditions need to be slightly abnormal with very clear skies, relatively dust free atmosphere and without mist or haze. This means that the sun is brighter than normal at low altitude. The flash is caused by refraction of the upper limb of the sun and is only seen when the rest of the globe is hidden behind the horizon allowing the green colour to be seen. The green refraction can then been seen as the brightness of the main globe of the sun is hidden and no longer obscures the green light. The same phenomenon can also been seen at the very moment of sunrise. So at 4.36am I was lucky enough to witness a green flash as the sun rose above the horizon on a perfect day. Observing a green flash at dawn is very rare as most people are not up early enough and you have to be looking at exactly the right part of the horizon at the time the sun first appears. I saw, for a fleeting moment, a brilliant intense deep green arc on the horizon that had a slight blue tinge, that then reverted to the normal orange colour of a sunrise. It was quite unexpected as despite looking at virtually every sunset for the last four months I haven't seen one, so to see a spectular green flash at dawn was a fantastic surprise. It has apparently never been captured on film and so it is sometimes difficult to believe it does acutally exist and not another seadog wind-up!. The sea is not needed for the effect to be seen and it can even created behind clouds. Interestingly a red flash can be seen if the sun descends below a bank of hard edged cloud near the horizon. Green flashes also occur with the moon and planets. The two people on the bridge were amazed to see it and certainly meant an auspicious start to the day for those who saw this spectacular phenomenon......
In case of breakdown in the steering computer on the bridge, the ship has an alternative mechanism. The servos that normally control the rudder are disconected and manual control is taken over by someone next to the steering gear. Instructions are telephoned down from the bridge and the rudder is altered by means of a turning wheel. This system has to be tested and since we were in calm weather and a long way from any land it was duly attempted. The photo shows Ian Raper with head phones on trying to steer the ship. As there is no visual contact it is difficult to get the hang of. As you can see from the wake of the ship it as not as easy as it sounds!!
Above: Ian in manual control of the steering gear (L) and the wake of the ship. Click the images to enlarge them.
Happy New Year!!
Happy New Year to all our readers around the world from all the crew. Whilst bobbing around somewhere in the Drake Passage we celebrated in the traditional way by ringing in the New Year. After finding out who the youngest and oldest on the ship at the time were, everyone one climbed up to the forecastle where the ships bell is hung. Paul gave us a countdown from the bridge and at the precise moment, three hours after old blighty, David rang out the old year and Tom Elliot rang in the new. Hugs all round then back inside to toast 2003. We were watched by about 50 black browed and wandering albatross who were sitting on the calm sea around the ship and looking quite ghostly in the ships lights. I'm sure all the free spirits of dead bosuns would have appr0ved of our methods of celebration!!
Antarctic circumpolar current
This week Sheldon Bacon and his team have been continuing the work that the Southampton Oceonography Centre have being running for the last few years. The Antarctic Ciurcumpolar Current (ACC) is a flow of water that runs from west to east around the entire continent. Below is a diagram of the ACC and one can see that the narrowest point in the cycle is at the gap between South America and the Antarctic Peninsula.
This is the Drake Passage and it forms a key choke point for the current. The ACC is huge and is in the order of approximately 130 million tons of water per second. The Drake Passage therefore is a great area in which to study the flow of water in the ACC as it all happens in a relatively narrow area.
To study the water Sheldon's team uses a few sensors on the end of a long wire. Basically there are three probes that measure the conductivity of the water, the temperature and the depth of the probe. Hence the imaginative name for it is the CTD. Below is a picture of the gizmo being lowered over the side on its way down to a depth of 4000m.
Once the three measurements are made, then using a clever formula the density of the water can be calculated. Ah ha, I hear you say, what is the point of knowing the density? Water will flow from an area of high pressure to low pressure and since pressure is related to density then one can predict where the water will be flowing. By making a series of measurements at different points and depths across the Drake Passage a map can be produced showing the different areas in 2-dimensions. Below is an image of water temperature across the Drake Passage.
The cold (dark blue) Antarctic bottom water can be seen at the deepest depth, above which is the rising North Atlantic Bottom Water (green) and at the top is cold surface water that is cooled by ice and evaporation. Similar charts can be made for salinity and the currents then calculated. The whole point of this research is to measure varitability in currents and try to correlate change with other indicies in global oceanography and climatology. The ACC is crucial to temperature movement around the globe this will be important in the understanding of global climate change.
Thankyou this week: to Captain Burgan's crew.
Coming up next week: Science!