Day 25th: 19th April 2008
Macquarie Ridge Current Meter Pentameter: Mark Rosenberg
Retrieving the moorings.
It's a sunny and wonderful day for some mooring recovery play so let's call out the crew for something to do and hear what they all have to say. (1)
The mate is there up on the bridge, steering us south down the Ridge. It's blowing a lot when he gets to the spot, so he alters the course, just a smidge.
The deckhands are standing about, so the bosun is starting to shout, (2) "Quit all ya blabbing, these moorings need grabbing"- he's laid money on how many come out.
"Get to work," calls the bosun, "understand? I want all those deck winches manned!" But they all have to wait, cos the mooring guy's late........then he appears, transducer in hand. (3)
Now the mooring guy's feeling a wreck. He's tired and he's got a stiff neck. He was caught unawares, then he tripped down the stairs, and wound up rear-end on the deck.
He hangs out the transducer string With the electronic ranging thing. (4) There's a hush all around, there's barely a sound....they lean in close.....he pushes a button..... and it goes "PING"
Now the moorings are terribly deep, deployed on topographies steep. He's been told by the boss if any are lost he'll have plenty of reasons to weep.
The mood was all tense round the ship. Did releases successfully trip? (5) The wait was so long surely something was wrong, so the crew started giving some lip.
"Ya blew it, ya dumb Aussie pranker!", (6) they cried full of malice and rancour. But deep down below the mooring let go and drifted away from the anchor. (7)
"Thar's the floats, ahoy and avast!" (8) came the cry from aloft in the mast. With the mainsail unfurled the grapple was hurled and the floats were hooked up as we passed.
Then there's hauling, unshackling and spooling, (9) with the wind and the spray and the cooling. It's rattling of chains, and unhooking vanes, (10) (and thinking of lunch without drooling).
It's done, and all of it's back, the lines are all hanging slack. The crew are at ease and the mooring guy's pleased....cos maybe he won't get the sack.
Footnotes (and apologies)
(1) In oceanography, a "mooring" is a string of equipment that's anchored to the ocean floor. There's an anchor at the bottom (just a big weight), and above it there's a long vertical string of floats and delicate measuring instruments. The whole string can be a few kilometres long, standing vertical, but the shallowest float at the top of the string is still a few hundred metres below the surface. So the string is attached to the anchor with a device called an "acoustic release", which let's you find the mooring and then get it back. You can communicate underwater with the acoustic release, and it'll tell you how far away it is. And when you send it the right signal, it lets go of the anchor. The floats then bring everything back to the surface, leaving the anchor behind.
(2) Just a bit of fun - the crew work very hard, and the bosun asks very nicely.
(3) A transducer is like an underwater microphone/loudspeaker. It's used to communicate with the acoustic releases.
(4) The transducer plugs into an electronic box. When signals are sent from the box, you can find out the "range" (how far) to the acoustic releases. Each "acoustic" (sound) signal that is sent is called an acoustic "ping".
(5) First you tell the acoustic releases to let go of the anchor, then you cross your fingers and pray.
(6) Adult version of this verse available to over 18's.
(7) If the acoustic release works and lets go of the anchor, the floats will carry everything back to the surface.
(8) A bit of fanciful romance for the old days here. Nowadays people stand in comfort on the bridge, peering through binoculars trying to spot the floats. And Tangaroa's got an engine, no sails.
(9) The mooring line (rope or wire) is wound up, or "spooled", onto a winch. As each piece of equipment comes to the ship it needs to be unshackled from the line.
(10) "Current meters" are used to measure (you guessed it) the water current. The older type of current meter has a spinning rotor to measure current strength, and a "vane" to measure current direction. The vane is like a weather vane that you might see on the roof of a house - a weather vane lines up with the wind, while the vane on a current meter lines up with the water current. Newer kinds of current meter use an acoustic signal to measure the current. The other kind of instrument on the moorings is a "thermosalinograph", measuring temperature andsalinity. Just like a mini CTD (if you've read about those).
Wind: 30 knots (WNW)
Air temperature: 3.9ºC
Sea temperature: 3.8ºC
Air pressure: 989 mbar
Position: 59º35.84 South, 160º0.39 East