Our final newsletter finds us close to the Falkland Islands; the end is in sight. It has been a busy and eventful week.
Weatherwise we have had our first and only sunny and calm day, plus a few grey drizzly days and a few windy and rough days. We have seen wandering albatross, and, highlight of the week, three fin whales only a couple of hundred metres from the ship. They stayed with us for several hours, seemingly racing us along during steaming, and coming close to investigate the CTD during stations. We wondered what they made of the CTD package pinging away as it descended.
Since writing the last newsletter, we have been continuing CTD stations westward along the crest of the North Scotia Ridge. There has been much discussion and betting on the location of the Polar Front. This can be seen as rapid changes in the temperature and salinity data from the CTD, or as strong currents measured by the ADCP. As it turned out, all of us were right! We crossed the Polar Front (or rather branches of it) and back again so many times that we all lost count! This will be a challenging data set to analyse?
Our final burst of effort has been Shag Rocks Passage, in many ways the most important region of the whole cruise for us, and the most critical to get right. We did closely spaced stations, stopping every time the depth changed by more than 500 m. We have a marvellous instrument called a multibeam echo sounder that produces a picture of the depth of the sea bed for about 3 km either side of the ship as we go along. It is fascinating to watch the sea bed unfold on the screen in front of you. It has proved invaluable for locating steep slopes near stations.
In Shag Rocks we deployed an array of moored instruments. Previously, there has been only one current meter mooring deployed in the middle of the Passage by a group of German oceanographers between December 1979 and November 1980. We have installed two bottom pressure recorders on either side of the Passage, to measure the variability in water transport. We deployed 6 moorings with current meters in 4 different locations across the Passage, to measure the flow, temperature and salinity. This was a mammoth effort by Ian and John from Southampton, and all the deck crew, working day and night. Each of the moorings is in about 3 km of water. The moorings have railway wheels as anchors. Instruments are attached to a wire which is suspended from the sea bed by a large orange buoy (some of which contain an upward looking ADCP). We hope to recover the moorings in about 18 months.
On Thursday evening there was the formal end of cruise dinner, when the officers dress up in their finest and the scientists dig out their one tie and slightly less scruffy attire. Unfortunately we had not yet finished science so it was it was a little less celebratory for us with three people on their shift and unable to come. There were just 2 CTD stations remaining. The Captain, Dave (who popped in from his shift) and the doctor gave short speeches of thanks. Afterwards everyone retired to the bar for drinks on Dave, Karen and Mike as a thank you for everyone's hard work. The final CTD station was to be number 069, a repeat of the station number 018 after which we broke off the section due to the bad weather, what seems like months ago but is actually less than 2 weeks ago. As the CTD package was being winched upwards from the deck, the cable parted. At this point we decided to stop science and set off to Stanley.