Day 11 Seeing through the fog
The weather is harsh today. The sky is low, dark and misty. Rain tumbles
down over the deck. Winds of 30knots
lash the sea causing rippling pulsations along the surface. If the scene wasn’t
hostile enough, a floating Eagrit is seen from the observation deck. It is one
of the birds we had seen a few days earlier, disoriented having lost their way.
It has not been able to stay in the air any longer and will now surely drown.
Photo: Not much hope left for this little
one.
The swell is modest so we can continue to
take water samples. The VMP – the device which is used to measure turbulence –
is held back. Because the VMP is released and then recovered, John and Alex
(its custodians) are reluctant to deploy it if there are too many whitecaps or
a thick fog. Both of these would make it all the more difficult to find on
recovery. This frustrates Jean-Baptiste
and many of us. A major focus of this project is to measure mixing of the blob.
But, to reconcile these, we need direct measurements of that mixing. In the mid afternoon the weather is rough but
the forecast good, so we give it a go. The mist thickens into the night and the
VMPs fate is on tenterhooks. All lights are turned off on the bridge and we
scour the opaque landscape. Finally, a flash from its light is spotted. The VMP
is not lost and another precious measurement is taken.
Photo: Andrew and Jean-Baptiste ‘wake-up’
and ARGO float.
Between measuring the blob and turbulence
etc. we are contributing to a broader oceanographic mission. We have on board 6
autonomous buoys called ‘Argo floats’. Up until the early 00’s, if you wanted
to know what the temperature and salinity was in the ocean, you had to go out
on a boat and measure it - like we are doing now. These days most of it is done
by ARGO buoys. Thanks to advances in technology, satellite communication, a
fair amount of money (driven by a real need to understand the ocean’s role in
climate), and collaboration between all the major oceanographic centres in the
world, ARGO floats are now everywhere.
Photo: Deployment of the float.
An ARGO float is basically a thermometer attached
to a big piston. The piston compresses a fluid, which makes the ARGO float
dense, so it sinks. When the piston is released the float is more buoyant so it
floats to the surface. When at the surface, ARGO buoys can send messages via satellite
thanks to what is effectively a mobile telephone stuck to the top. They phone
home to let us know how warm it is in the deep ocean. So they are bit like a
teenage son or daughter away on a gap year. You can’t control where they go but
can only hope they will phone home from time to time to tell you how they are
getting on (collect calls only…of course).
Image: Distribution of ARGO floats by the
country that deployed them. There where more than 3000 in 2010. The serial
numbers on ours reads close to 6000.
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