Aug 28 - Sea trials
1200 Position: 56°17'N 009°36'W - 117 Nm from Stornoway
Air temperature @ noon today: 15.5°C
Sea temperature @ noon today:13.6°C
Wind: SSW, Force 4
Barometer: 997.2 hPa
At long last the James Clark Ross is back at sea, with a large number of scientists and technicians onboard, undergoing sea trials following on from the annual refit in Portsmouth.
Following load testing and Lloyds Register certification of the refurbished Mid-Ships Gantry the ship departed Portsmouth on Wednesday morning and headed towards Portland to take on bunkers (fuel). The passage was a bit lumpy as the wind had picked up, with gusts up to 35 knots, and we arrived in Portland at about 1600.
The ship loaded almost 900 cubic metres of fuel, taking four hours to do so, and departed Portland at 2200. Our next destination was Cork, with sea trials to the ship's dynamic system being carried out on the way. Whilst approaching Land's End an unexpected visitor, in the shape of a Royal Navy Sea King helicopter, arrived and asked permission to carry out some manoeuvres on our Aft Deck. Initially we had hoped that they would be winching a man down onto the deck, but in the end they just lowered some weights down towards the deck and then back into the aircraft. This was repeated a few times and then they headed back towards land.
Our visit to Cork was to drop off one technician and collect another (from the same company, but different departments!). The ship entered Cork Harbour and held position using the Dynamic Positioning System just off of the Whitegate Oil Terminal for the boat transfer of passengers. Within thirty minutes of entering the harbour the ship was heading back out to sea, following the coast of Ireland around to the west to the next trials area.
Saturday afternoon saw us in approximate position 56N 010W where we conducted trials of the ships new Acoustic Doppler Current Profiler, which provides detailed maps of the distribution of water currents and suspended materials through the water column and along the ship's path. Also put through it's paces later in the day was the newly fitted Acoustic Reference System (ARS). This involved deploying a transponder to the seabed, some 1000m below us, and then interrogating this using the ARS.
The transponder is weighted down with sandbags and fitted with a flotation collar. Due to the trials finishing late on Saturday it was then too dark to recover the transponder and this was left on the seabed overnight. At 0600 this morning, when there was sufficient daylight to start the recovery, the weather had worsened and the wind was blowing at up to 45 knots and the sea state was far from smooth.......which is what one really wants to spot anything in the water. By sending coded signals to the transponder it breaks free from the sandbags and then floats to the surface, where it proves difficult to see. However almost as soon as it popped up the Captain spotted it (he is nearly always the first one to spot anything that is being recovered from the seabed!) and the ship was maneuvered slowly alongside the transponder which was then lifted aboard.
Also being trialled during this trip is the Swath bathymetry system, which is used to map the seabed.
All these systems are 'acoustic', which means that they send sound through the water and then analyse the return 'echo'. In order to get the best results the correct value for the speed of sound through water needs to be known. A general figure of 1500m/sec can be used, but by sending down a Sound Velocity Profiler it is possible to calculate the correct value. This value will change depending on such things as location and temperature.
With the change in the weather the ship is now heading for the next port of call, Stornoway, where a passenger exchange will take place. All the trials personnel will depart the ship here and the remaining scientists for the Arctic cruise, JR127 SAMS (Scottish Association for Marine Science) will join.
As we are now back at sea there are two internet links to remind you of:-
The Northern Lights by Naomi Asia Huntley
Like dancing fireflies in the dim of night
Like a million stars shining bright
Or a colour changing eye in flight
Then closing to put a stop to sight
Like the mid-morning sun
They wave good morning
Or like a ink blotted sky
It deepens to reveal a surprise