22 November, 2014 08:49

Ocean research cruise blog of Jonathan Sharples

 

We had a very successful day yesterday – managed to get through all that was planned, plus most of what I’d planned for the next day as well. Deploying the moorings began shortly after 0800. This tends to be a long, careful process as the mooring wire is gradually unwound over the stern, instruments are clamped onto it at the planned depths, buoys are slotted in at key stages to hold it all up in the water, and then finally the 500 kg clump of chain is attached and dropped into the sea. By lunchtime we had deployed the long temperature/salt logger mooring and also the bedframe with the current meters. The second current meter mooring has been delayed until today, while the techs sort out an issue with the memory cards that it uses. That allowed us to go and hunt for the wandering wirewalker mooring and also the glider that we deployed when we first got here from Falmouth, but which has refused to dive.

Both the wirewalker and the glider have been sending us regular position information via a satellite link, which meant that finding them and getting them on board was very quick. We arrived back at the mooring site just after sunset, ready to do some more zooplankton work.

It’s a lovely day today – a glorious sunrise (complete with dolphins) and an almost flat sea. However, we’ve just heard that the long-term forecast is looking a little grim. A particularly nasty-looking low pressure system is due this side of the Atlantic next weekend. Forecasts that far out tend to be a little uncertain, but it’s worrying enough for us to think carefully about when we can get back to this site to recover the wirewalker and the 2 gliders that are here.

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Glider away….

Ocean research cruise blog of Jonathan Sharples

 

Two new pieces of equipment deployed yesterday. First, the Ocean Microstructure Glider (OMG). A glider does exactly what the name suggests – it glides through the sea. By making itself heavier than the water, and tilting its nose downward, it glides downwards. Then, when it gets to the depth at which it has been instructed to turn round, it makes itself lighter than the water, points the nose up and glides towards the surface. Inside a glider are instruments similar to those on the CTD – measuring water temperature, salt and plankton. The OMG also has some specialised instruments for measuring the amount of turbulence in the water. That’s what the “microstructure” part of the name refers to – the sensors measure tiny changes in water currents associated with turbulence. We are really interested in turbulence, as it mixes nutrients, plankton and carbon through the water. The really neat thing about gliders is that when they surface they can stick their tail end out of the water and communicate back to shore via a satellite link, transmitting data back and also receiving new instructions. Our gliders are not controlled by us on the ship, but by scientists back at the National Oceanography Centre in Southampton and in Liverpool.

wirewalker deployment

 Immediately the glider was away, we moved the ship clear and deployed a “wirewalker” mooring. This again has instruments for measuring temperature, salt and plankton, but it moves up and down a wire fixed to an anchor on the seabed and a buoy at the sea surface. The action of the waves on the buoy provides the energy that the wirewalker needs to ratchet itself down the wire (so, a note to my nephew Ben there – yes we do now have things that use the waves’ energy to power them! Your idea was spot on); it then releases its grip on the wire and floats back up to the surface. With decent waves (of which we’ve been having plenty) the wirewalker can profile up and down the cable every 15 minutes or so. Jo Hopkins for the National Oceanography Centre in Liverpool is running this instrument – she is keen to capture the details of how the water is mixing as the weather cools into winter.

omg glider deployment2

 
We’ve lost a lot of our communications at the moment – certainly internet and phones are out. Zoltan, the NMF computer tech, is working through all possible causes and he’ll be calling on the ships ELT tech as well. Hopefully we’ll be fixed soon. We still have access to the National Marine Facilities Webmail though, so I can get these posts through OK.

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omg glider off