….. or legs?
Having returned from Caldera, after towing the chase boat there, we have undertaken a phase of instrument recovery. After that will be a bit more data acquisition using only a 3 km-length of streamer as the chase boat’s engine is not yet repaired and so we cannot use anything longer!
This phase of recovery focused primarily on the instruments of the other group here as theirs have onboard timers which will release the instruments from the seabed at a date and time that is set before the instrument is deployed.
As this date/time is drawing closer, they will be the focus.
However, we do have a number – seven – of our instruments interspersed in between which it makes sense to also recovery during this phase for time efficiency.
Is that a lucky seven?
The sea state and weather in the work area have been very clam and clear and this makes recovery relatively straightforward – the hardest bit is the waiting – waiting for the instruments to rise through ~5000m of water once released from their anchors.
This can take several hours, which is time for quite a few cups of tea!
Seeing the first arrive of any recovery set is always cheering – one down and six more to go.
The freeboard of the RRS James Cook isn’t that great compared to some vessels we work from – but it is still enough to make the grappling for the recovery line challenging and also tricky to stop the sway once caught and plucked from the sea. The flotation is glass and the last thing we want at this point is to smash it against the ship’s hull.
Once lifted to deck height, it is then just a quest of swinging it inboard and dropping it onto a pallet on the deck, ready for a quick wash down with fresh water.
No sooner is the first back, then a short vessel re-positioning transit to the next and that too is plucked from the sea.
The seabed in the work site is oceanic crust made of basalt, but given its age it now has a nice drape of sediment on top.
Sometimes, if the sediment is particularly soft or gooey instruments sink into it and on recovery bring back a sample inside the black tubes.
One after the next returns and is stored in the shipment racks ready to be sent home. It is always very pleasing to count back in those that were counted out, and watch the racks progressively fill up.
And all seven are recovered …..
….. together with a compliment of much bigger and heavier instruments from the other group.
The sun having set on this recovery phase, we return to some more data collection using the 3 km-length of streamer until the 6th January, when all remaining instruments will be recovered.