D334: Monitoring ocean circulation in the Atlantic


Cruise diary

23 November 2008

Craig writes...

"Our work on the ‘mini-moorings’ is now complete! This has seen us cruise right into the shallow coastal waters west of Morocco to depths of as little as 100m.  This area is heavily fished and whilst it is nice to see some sea traffic, and signs of civilisation after the mid Atlantic, this isn’t such good news for the moorings. Fishing nets can easily become snagged in the mooring gear at such shallow depths and this likely explains why our acoustic signals to two of the moorings have gone ominously unanswered.  Still, to loose but two of the smallest moorings throughout the whole cruise means the mooring operations have been a great success.

Sailing into shallower, more productive, water has also meant much more by way of wildlife, with seabirds now to be seen tracking the ship, perhaps mistaking us for a fishing vessel and hopeful of a free lunch.  Pods of dolphins, too, have made an appearance.

Right: A mini-mooring plan. Sitting in shallower depths than the tall moorings, they can afford to use lighter-weight gear, such as the release device attaching the wire to the anchor.

The final scientific task for the cruise now is to complete a series of CTD casts running in a northeast-southwest line south of the Canaries.  These won’t carry any microCATs, but rather are being completed in order to compare temperature and salinity properties of the coastal slope with historical experiments – the last one being run in 2004. Like the mooring information, all of the data gathered will help us to determine how the Atlantic ocean behaves at the oceanic boundaries to enable continued and more precise monitoring of the overturning circulation.

Left: The final science task – to complete the CTD line south of the Canaries.

The CTD operations are scheduled to finish sometime soon today. Once the final data are processed and checked, we’ll begin to dismantle the science lab, and pack up our gear. The ship will swing east and begin a 19-hour transit – its final course to Santa Cruz, Tenerife!"

Left: Stuart oversees the recovery of a mini-mooring. Looking back from the aft-deck you can see the winch-house, jutting out to the right. This is where the CTD winch is operated from during the descent and ascent of the frame during a cast.

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