4 March 2010
When the “rosette” yields to the Compass Rose…
The little technological marvel that is the “rosette”, nickname for the CTD (Conductivity-Temperature-Depth measuring device and the rosette of sampling bottles) is finally in use once again! But it certainly wasn’t an easy feat.
“We’re back in business!”: A man of action, captain Hervé Bourmand doesn’t try to hide his satisfaction. Ever since mid January, the rosette has remained dry. After a month and a half spent analyzing corals in the Djibouti area and making supply runs, the serious stuff is finally starting. The baptism of the CTD-rosette -which is at the heart of Tara’s mission- was originally planned for the night stretching from Wednesday to Thursday, right after our departure from the Persian-Arabic gulf, the crossing the strait of Ormuz and arrival into the Gulf of Oman, antechamber of the Indian Ocean. No more closed seas for us!
Ever since casting off in Abu Dhabi, sailing against the wind, Tara was going full blast using both sails and engines. However, as the Omani island of Great Quoin -the eastern extremity of the Arabic peninsula- was drawing closer, the winds turned and grew stronger.
These were ideal conditions for us to switch off our two diesel engines, something which everyone rejoiced about! Towards the end of the evening, the scientific team got together to set the agenda for this leg of the journey, during which, after quite a break, our sampling and filtration program is starting up again. The launch was then planned for 2.00 AM, and required the presence of nearly everyone onboard. Those who could quickly tried to stock up on a few hours of sleep, in prevision of the short night awaiting us.
Unfortunately, the wind kept on getting stronger. At midnight, it was blowing at a strength of about 25 knots, and the trough of the waves reached over 1.5m. Tara kept going steadily, at an honorable speed of 9 to 10 knots, even as the oil rigs, hydrocarbon shipping terminals and moored ships increased in number between her starboard side and the coast, and as traffic around her grew denser.
Cargo ships passed us, less than a half mile from our route: one of them even seemed to be heading straight towards us until it veered off at the last second and hugged our starboard side instead. The wind reached 35-40 knots, the troughs reached over 2.5m, breaking over Tara’s hull.
We hauled the genoa down to install a trinquette instead, in order to avoid excessive solicitation of the rigging.
Because the manipulation a 130kg rosette in the middle of the night by a brand new crew would most certainly be very tricky, Hervé decided it would be wiser to not set up a sampling station in the area.
Together with Stéphane Pesant, scientific coordinator of the expedition, he mapped out a new destination for Tara, away from this busy area but just as close to the continental plateau. There’s a good reason for this: it is essential for researchers to begin collecting samples in shallow waters first, in order to analyze the changes as depth increases. It was then determined that the Rosette would be launched at 6am. Shortly after sunrise, the device, charged with its bottles and various sensors was lowered into the water, as if for a baptism, Coordinates: 24°54’767 N et 56°52’878.
Thus, the CTD has re-begun its long task of observer of the oceans of the globe .When hauled back up to the surface 26 minutes later, Marc Picheral – the engineer- was a long way from trying to hide his satisfaction: “it’s very nice to see that all the sensors are working, even though they hadn’t been used in more than a month: all you have to do is press on the button and it comes out!” Immediately after that, sampling and filitering took over: But this here is only the beginning, the analysis is to be continued in various parts of the world, in different labs!