Thursday, January 8, 2009

cruise objectives, part two

Drilling down a little on the broader goals -- which I now know were
posted -- we've got three distict groups of scientists on board. Even
though to an extent we are all driving at the same questions, the
methods and instruments we're using and the (small?) picture goals
differ. The physical oceanographers on board are most interested in
the heat and currents in the subsurface ocean (below 200m or so). To
learn more about these, we use everything we can; there are at least
5 instruments on board -- a CTD/Rosette, ocean floor moorings, an ice-
tethered profiler, multibeam swath sonar of the ocean floor, and an
AUV (autonomous underwater vehicle) which can travel ~10 hours on its
own collecting data (see link to the Autosub on the right). The CTD
measures temperature and salinity as it is lowered to the ocean
floor; the rosette collects water in 24 bottles from different depths
(more in previous blog from 2007). Moorings record temperature,
salinity, and currents for long after we leave, but they have to be
retrieved by other ships to see the data which they collect. The
"ITP" is like a mooring except it is attached to ice and can move up
and down on its own in the ocean beneath the ice. Since the ocean
floor is important to the control of currents, recording the
bathymetry (wikipedia?) is helpful for understanding why we see what
we see. On this cruise, I am monitoring and analyzing some of the
data and samples from the CTD, so will probably spend more time on
the details relating to that work.

I am less clear on the goals fo the other two groups, studying sea
ice and surface biology. Some of these scientists will give talks
about their work over the next few weeks and I will know more soon.
Briefly, the sea ice crew is going to core ice floes to analyze their
composition and thickness. They will also deploy "drifters" to
measure location, snowfall and meteorological conditions as the ice
floats around. One of their activities -- that everyone is
participating in -- is hourly observations of the types,
concentrations, and thicknesses of sea ice that we pass through on
the ship (not happening yet!). The biologists are most interested in
the nutrient concentrations and type and distribution of
phytoplankton, and will collect, filter, and analyze these on board.

Right now we are cruising on a straight line (actually a "great
circle" -- extra credit!) towards the nothern portion of the amundsen
sea. We have, as I write, over 1200 kilometers to go. At a speed of
18 km/hr or so, weather permitting, we'll make it within 3 days. For
those who were curious, I'm not sure whether we will dawdle there.
Since there is sea ice around there as well as potential sites for
mooring deployment, there may be a reason to stay and work. However,
there's no guarantee that the Pine Island Ice Shelf -- our end goal
500 km further south and where much of the work will take place --
will remain ice free.

More about the plan of action when I learn it (sorry Rich, I'll know
soon...). We've got at least 3 days of wavy ocean to consider it.

There is a sextant on board, although I had to ask -- I didn't know
we had one, much less know how to use one. I've been reassured that
it's part of the licensing process for captaining one of these ships,
so rest assured, tortoise and class, there are still people who know
how to use these if we lose our other equipment. What they're
learning in school IS useful.

And erika, you get the extra credit for figuring out what a nunatak
is (and for spelling it right). The extra credit is ... maybe I let
you win at scrabble next time we play.


  1. Hey Chris! This is so cool. I love getting to follow along with you. I have to admit, from all the way up here in Oregon, it all seems a little surreal and like you're telling me bedtime stories, but then I remember that you are actually THERE, and that makes it cooler.

    Thinking of you!

  2. Could we persuade you to capture an image of the sextant(perhaps the captain posing?) and CTD? We would like to compare the sextant to our astrolabes that we are using to measure the solar angles between equinoxes for our project and the CDT to the one I used with the Cal Current survey. (It was really big.)