Friday, February 6, 2009

Emperors and the ITP

We've deployed nine moorings so far on the cruise. Each one has been
sent over the side of the ship with a large concrete block connected
to a series of CTD-type devices via a rope and some floats. The
instruments are fixed at specific depths in the water column to
capture features of interest -- in the case of those deployed near
ice shelves, where models and observations imply that most of the
heat flows under the ice and meltwater flows out.

These will provide a long and continuous time-series of data that
will help us interpret tides, seasonal variations in flow and water
properties, and longer-term trends. However, the two biggest
downfalls about moorings is that information that they provide is
limited to specific depths and the data is not available until they
are successfully recovered. Given the obstacles to successful
mooring recoveries here (sea ice, bad weather, moving ice shelves,
etc), it is a huge benefit to be able to see the data in real time.

Enter the ice-tethered profiler...

which sits on top of the ice with a wire dangling below. Once a day,
a CTD device runs up to the just below the ice and down to the
maximum wire depth, giving a complete picture of the "water column
structure". When it reaches the surface, it sends a satellite signal
with the data it has collected that day. Up to this point these have
only been used in the arctic, where ice sticks around for longer.
However, some sea ice in the Amundsen is "fast ice" -- meaning it is
connected to the land (or ice on the continent). Because it is not
subject to waves and crashing into other floes, it may stay in one
frozen piece for many years. Yesterday several brave souls took a 3
mile ski-doo from the fast ice edge into a suitable site and
assembled the device between two ice shelves (the Thwaites and the
Crosson). A long day for those involved.

For those who weren't, the gangway was rolled out onto the ice and we
played with penguins. Actually the rules of the Antarctic and the
USAP do not allow us to play. It's more a game of mutual checking
out and bemusement. They chuckle at us in our matching orange float
coats and clumsy boots, and us at them in their bottom heaviness and
incredibly flexible necks. Emperors this time -- flashes of orange
and yellow tastefully integrated into the more traditional black tie.

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