18 Mar - Last Call at Rothera
RRS Ernest Shackleton Diary
Position @ 1200 UTC - 3 hours: 62°21' South. 058°34' West.
Next destination: East Cove, Falkland Islands.
ETA: 20 March 2001.
Distance to go: 636 nautical miles.
Total Distance Sailed: 23,829.3 nautical miles (Since departing Hull, England on 19 October 2000).
Wind: S'ly, Force 3 to 4.
Barometric pressure: 982.3 mb
Sea state: Moderate, expected rough by late afternoon.
Air temperature: -1.3°C.
Sea temperature: +1.2°C.
Last weather observation sent from the RRS Ernest Shackleton
At 0600L on Monday 12th March RRS Ernest Shackleton entered the Pendelton Strait and slowly made her way towards Trump Island. Earlier in the season a Low Powered Magnetometer had been placed on a section of rocky foreshore and had been collecting date throughout the summer months. This instrument is designed to measure the earths magnetic field and there are also similar devices at Port Lockroy and Rothera. Trump Island is about half-way between these two.
The data are stored on a memory card and all that is required is to change the card over. This is a simple job if the weather is fine (and we were lucky in that it was dry) but had it been raining it could have proved interesting. The position of the unit had been carefully noted when it was erected and we had it clearly marked on the chart of the island. Once we were in position off Trump Island everyone was looking for the instrument but could not see it. However, once the boats had got to the foreshore and dropped of two personnel to complete the job, it was very quickly found and the cards changed.
As you can see from the picture below, it is not a small item, but amongst the rocks and in dull overcast conditions it was almost impossible to see from the ship. Within an hour everyone was back onboard and we headed towards Rothera.
The LPM on Trump Island and Jim Fox collecting the data.
Low Power Magnetometers - by Jim Fox
As the name suggests, a magnetometer is a device for measuring magnetic field. Different technologies can be used for the actual sensor but, simply put, a magnetometer is a highly sensitive electronic, often three dimensional magnetic compass.
The Earth's magnetic field is not constant and is influenced strongly by the Sun and plasma which is emitted from it. When an influx of plasma from the Sun comes into the proximity of the Earth, the magnetic field of the Earth fluctuates. Although these events are happening many tens of kilometres up in the atmosphere, the changes in magnetic field can be detected by magnetometers on the Earth's surface. This area of upper atmospheric science includes the study of these interactions between the Sun and Earth (often termed 'space weather'). Electrical storms, satellite and radio communications problems and aurora are a direct result of these influxes of plasma.
Magnetometers are far from a new idea and have been providing some of the most important data for many decades, allowing scientists to get a better idea of what goes on 'way up there'. However, what is new about the magnetometers which have been deployed this season is that they have been designed as very low power, quick to deploy, stand alone, low maintenance units. They use a solar panel for power and rechargeable batteries for when there is no Sun; quite a problem in Winter the further south you go in Antarctica. Hopefully, these units will produce data for a good number of years.
Because interference from electrical equipment causes changes in the local magnetic field, magnetometers are usually positioned remotely, well away from other power sources or areas of activity.
Three low power magnetometers were deployed on the Peninsula early this season by RRS James Clark Ross, with more being put further south on the Antarctic plateau. They need accessing once a year to extract the data which have been logged and this is why RRS Ernest Shackleton was needed at Trump island. The memory of the logger has now been replaced and will not need accessing again until next season. The data which have been gathered over the Summer season since deployment will go back to BAS HQ for analysis by upper atmospheric scientists to enable a better understanding and, eventually, prediction of space weather.
Both RRS James Clark Ross and RRS Ernest Shackleton are fitted with magnetometers and these are used to obtain data as the ships go about their tasks. Onboard the data is saved to a conventional hard disk and then downloaded to CD for sending to Cambridge to be analysed.
Once the Humbers were back onboard RRS Ernest Shackleton set course for Rothera, taking the 'outside' route to the west of the Peninsula. This meant that we were once again in open water and there was a deep swell running causing the vessel to cork-screw a little. During the afternoon a pod of about a dozen minke whales was sighted, about two miles from us, and they slowly passed down the port side of us.
Tuesday morning we approached Rothera, on Adelaide Island. As usual there was a large crowed gathered to greet us as we made a slow approach to the Bisco Wharf. By 0930 we were alongside and getting the lines ashore and by 1000 we were discharging cargo to the shore. All the Rothera cargo was discharged by the end of the day, this leaving us with loading cargo for return to the UK, waste from the base and fuel to be pumped ashore.
Wednesday saw the final cargo coming onboard, including a number of vehicles for return to the UK. The weather continued to be disappointing once again.
Thursday, our final day at Rothera, saw the live specimens being carried onboard to be placed into a purpose built container containing an aquarium. There will be an article on the aquarium as we head back to the UK. All the wintering personnel were invited onboard for a meal in the evening, which was much appreciated by all who attended.
Friday and it was time to depart. All those leaving were onboard for 0900 for a safety brief from the Chief Officer, John Harper, and once this was complete preparations were made for the departure of the vessel. Most of the winterers were down at Biscoe Wharf to wave goodby to those leaving and the lines were let go by 1000 and RRS Ernest Shackleton slowly steamed away from the base.
At 1100 a fire/boat muster was held so that everyone knew what to do and where to go in case of an emergency.
By the middle of the afternoon we were once again in open water and rough seas, causing the usual motions that we so love onboard here. Needless to say a number of the new passengers were not seen. The journey time to Jubany (an Argentine base on King George Island), assuming good weather, was about 1 day and 18 hours away. With the poor weather this then became almost two days, with RRS Ernest Shackleton approaching the base, in Potter Cove, at about 0900 on Sunday morning.
We are calling at Jubany to uplift five personnel, three Germans and two Italians, who have been working at the base during the summer. The Germans have been working here for a number of seasons now, coming in for the summer months only and this is becoming a regular call for us.
The good news was that in the early hours of Sunday morning we found the shelter of King George Island and so the motion suddenly stopped. Somewhat blissful, especially for those who had been confined to their bunks since Friday afternoon. However, along with the calm seas came snow and poor visibility. The decks of the vessel had turned white and were somewhat slippery first thing in the morning. The snow was very powdery and no good for snowballs!!
RRS Ernest Shackleton made a slow approach to Potter Cove, King George Island, in poor visibility arriving on station at about 1000. At anchor in the cove was the Puerto Deseado, an Argentine survey vessel, who was intending to depart later in the day and head across the Drake Passage.
Two Humber inflatable boats were launched to go to the beach to collect the outgoing personnel and their belongings. This took a number of trips to complete.
The Antarctic Pilot describes Potter Cove ' ...(62°14'S 058°41'W) which lies on the NE side of Maxwell Bay, has been described as the best harbour on this coast, being well sheltered and round, and providing anchorage in a moderate depth, the bottom being good stiff clay. The harbour may be known by a remarkable hill, called Three Brothers Hill, on which there is a cairn, 1¾ miles NW of Stranger Point'.
There is also an historic monument in Potter Cove, being a metal plaque erected by Eduard Dallman to commemorate the visit of his German expedition, 1st March 1874, onboard the Grönland, the first steamship to reach Antarctica. The laboratory used by the Germans at Jubany is named after Dallman.
By 1115 the ship was heading back out to sea, shrouded in mist and making for the Falkland Islands.
Forthcoming events: Head for the Falkland Islands to off-load personnel and waste. ETA 20th March. On completion depart for South Georgia and Signy Islands.
The next page will be written on the 25 th March 2001 and should be published on the 26th March 2001.