10 May 2010
(updated 10 May 2010 at 12:01 UTC) »
The real ocean
For half a year I work at the KNMI now, working an modelling
of the ocean biogeochemistry, tending to use only free
software. Now for something in the context of my work which
is mostly unrelated to computing: a cruise over the Atlantic
to collect measurements!
Two cruises have been planned for the GEOTRACES project
for this year. One will cover the course
and the second the course Hamilton--Fortaleza. Before the
start of these cruises the equipment had to be tested on a
shorter cruise, which I joined. This small cruise started
from Texel and the original plan was to go to Reykjavíc
(Iceland). Here the researchers for the bigger cruises would
get on the ship. However, in view of the volcanic activity
on Iceland and all the air traffic problems resulting from
it, it was decided to go to Scotland instead.
We planned to leave the port at Texel on the 22nd of April
but, as often
happens with preparations, things got delayed. Added to
this, we needed
high tide to sail out to sea. This is why we left on Friday
the 23rd of
April. The North Sea was calm and the sun was shining. It
birthday, so we ate pie and I got a book which was later
everyone on board.
The next day the weather was grayer and I got sea sick in
such a way
that I did have a chance to participate in or observe any
On the third day, April 25, the Very Large and the Ultra
systems were let down and pulled up successfully. Both
24 samplers, each twelve litres in volume. The Ultra Clean is
especially useful for the measurement of metal
the system is mostly made of plastic to prevent the water
into contact with metal.
Leslie and Steven explained the CO2 measurements to me.
the alkalinity and DIC (Dissolved Inorganic Carbon), from which
concentrations of carbon dioxide, bicarbonate and carbonate
calculated. The most ingenious I found the measurement of
which first all ions are converted to carbon dioxide by
means of an
acid. The resulting liquid is radiated by light with the
wavelength where carbon dioxide molecules are ionised. Two
are measured per molecule. The electric current is
integrated by a
measurement device. The resulting charge can then be used
the number of mole of carbon dioxide, which is the same as
concentration from the sample.
In the evening there were two lectures; one presented by me
modelling of trajectories in the ocean, and the other by
the measurement of concentrations of silicium.
On the fourth day the sampling systems were let down a bit
one kilometre. An electric connector of the Very Large
seemed to be leaking. After the replacement of a rubber
ring there was
no more leakage.
In the end we managed to test everything with success.
interesting to see how the samples were taken, what can go
wrong and how
some of it is analysed. This gives insight in how difficult
it can be
to determine the properties of the ocean and how sparse data
compared to the enormous size of the ocean and the number of
data in models. Also it gives an idea where errors in
arise. In the morning of the fifth day, April 27, we sailed
Scrabster, a harbour on the far North of Scotland. Half a
went off board and new scientists went on board for the
cruise to Bermuda.