Tuesday, September 10, 2013

Cruising through the Bismarck Sea

We're cruising to our next site through the Bismarck Sea north of New
Guinea, and haven't dropped a core since 4 yesterday morning. The
night shift took care of that one, and we've had very little to do

Today our A-Team (the midnight to noon watch, which apparently it is)
had an awesome, if not incredibly hectic and tiring, work shift! The
five of us (Jeremy, Kelly, Sam, Debs, Ryan and Greg) worked all
through the night sampling, recording, and sectioning all three of the
coring methods available to us on the ship.

The night started right as the multi-corer was being pulled from the
water. As soon as it hit the deck, the five of us were ready to go,
archiving the four longest cores, and sampling/slabbing the remaining
four, for a total of eight cores with good mud recovery! The process
of archiving and sampling all eight took about 3 hours, a bit slow
because the five of us are new to the multi-core device and its

After the multi-core, we had three more cores to work with – the
trigger core, which is a part of the piston core system, the gravity
core, and the piston core itself. All of the cores came back with a
good amount of mud, much like the multi-corer, with recovery lengths
of 4.1 m and 11.45 m for the gravity and piston cores, respectively.
Our team sectioned each of these into 150 cm sections, and now they
are prepped and ready for the multi sensor track! Overall, it was a
very productive night, leaving all of us happy, tired, muddy, and
ready for bed!

The subsequent noon to midnight shift (Chris, Clara, Clint, Angel,
Kim, and Yair, who are secure enough in their competence that they
don't feel the need to give themselves a self-congratulatory
nick-name) was very slow. There's some work in the lab, but we are
neither sweaty nor covered in mud. We did stop to take a CTD
(Conductivity, which gives you salinity, Temperature, Depth) around
7pm. We lowered a rosette (a large cylindrical frame) with instruments
to measure temperature, conductivity and depth and 24 niskin bottles
(spring-loaded bottles which are lowered open and triggered to close)
which can be closed at certain depths to capture water samples for
later chemistry analysis. The whole evolution has been a staple of
oceanographic research for decades, and it's how we know how
temperature and density change with depth in the ocean, and how we can
track water masses to map currents. In the plot to the left [update:
just kidding, the CTD log isn't on the ship's server yet. We'll post
one for you to see later. Sorry!] you can see the temperature profile
(red) of the water column with a mixed layer near the surface, where
wind and wave action mix the water and the temperature doesn't change.
The salinity (yellow) is lower at the surface because of frequent rain
here in the tropics. At about 80 meters water depth you can see a
sudden dramatic decrease in temperature. This is the thermocline, a
major density gradient in the ocean, and it corresponds to a salinity
maximum. This interval extends to about 450 meters. The salinity
minimum around 690 m is Antarctic Intermediate Water; we are along a
major passage north for AIW. Other than that it's been ping pong and
lab work. This afternoon we're going to start splitting the cores
(down the long axis) so we can describe them. It's hard to believe
we've only been at sea 4 days. With luck the sky will stay clear and
we'll get a good sunset. I woke up this morning and drank my first cup
of coffee forward with the whale watchers as we cruised along the
northern coast of New Guinea. It's a dramatic coast with tall green
mountains and palm trees along the beach. We're at one marine mammal
sighting, by the way. Gary saw some Spinner's Dolphins several miles
away from the ship this morning.

Posted by Chris and Jeremy