12 February, 2009 RRS Ernest Shackleton
SO WHERE ARE WE PRESENTLY ?
Presently, the RRS Ernest Shackleton is in the Weddell Sea of Antarctica. And what are we doing here ?
The Shackleton is primarily a Logistics Ship, and then we don the disguise of a ‘North Sea Rig Pig’ during the Summer months back up in the Northern Hemisphere, so it is delightful to actually be down South and doing some good science.
The Shackleton has one program of ‘bread and butter’ science that is carried out throughout the year, and that is the STCM or Shipbourn Three Component Magnetometer. The STCM measures the world’s Magnetic Field and we are constantly sensing and recording the ‘X’, ‘Y’ and ‘Z’ components of magnetism wherever we go in the world.
But apart from this program, the Shackleton is largely occupied with transporting food, equipment and passengers throughout Antarctica during our Southern Season. This year is different in that we have onboard Dr.Keith Nicholls and he and his team are conducting a program of science in the Weddell. That includes CTD’s (Temperature, Depth and Salinity Probes), Moorings, and Seal Tagging.
(Conductivity, Temperature, Depth) measurements are samples of the water column at various depths which gives indications of what the Weddell Sea is doing under the influence of the melt from the Ice Shelf.
The moorings are the underwater deployment of instruments to measure similar data, but they remain below the surface from year to year, and only upon recovery do they give up their treasured secrets. The problem here is that when the mooring is deployed one year, there is no certainty that the spot won’t be totally covered in sea ice the next year. We have just recovered one such buoy arrangement that has remained sub-surface for 4 years and was only this year accessible as we ploughed through stretches of Pack Ice in order to locate the mooring beneath. A remote signal activates a release mechanism to detach the package from it’s seabed weight. Thereupon it bobs to the surface – and hopefully into clear water and not under some inaccessible ice floe !
In a further effort to uncover the secrets of the Sub-surface Weddell Sea, we have taken to tagging Weddell Seals. It is a process whereby a small data logger/transmitter is mounted on a host seal and this will record where and when the Seal dives beneath the surface throughout the Weddell Sea. The results are amazing. Not only does it give more CTD data but is a window into the life of a Weddell Seal and how far afield it will swim in search of a good meal !.
The funny thing about our Seal Hunting adventures, is that in the Weddell Sea, it is hard to find Weddell Seals ! There are plenty of the crabeater variety, and even Leopard Seals, but in our search for 10 individuals, we have only managed to find 9 to date. The search continues as does the science.
We anticipate being out here in the Pack Ice and Floes until we return to Halley on the 19th of February, and then after a short 3 day stay, the Science program will continue onwards to Signy. Thereafter it is Stanley, Falkland Islands and the JRH Crewchange.