The Early Shift

Last night we steamed down the southern tip of South America, passed
Cape Horn and into the Drake Passage (picture above). Weather the last
two days has been fantastic. The seas are minimal, and yesterday
morning was bright and sunny. Science shifts started working
around-the-clock collecting water parameter measurements and air samples
once we entered the Drake Passage.

Our scientific team works with marine technicians from the R/V LMG in
3-hour shifts to collect samples and deploy Expendable Bathymetry
Temperature devices or XBTs. These are deployed over the side of the
ship while it is underway and a small copper wire, attached to the XBT
and temporarily to the ship, relays information back to the ship as the
XBT sinks. The XBT uses two copper wires tied together to measure the
current's resistance from different depths, which can be used to find
temperature. This same procedure is followed each time the R/V LMG runs
on this transect, creating a data pool of temperature from different
depths. Once the XBT sinks to 800 meters all the useful data has been
collected and it is lost to the Southern Ocean (hence Expendable in the
name).

This morning we also deployed a XCDT, which is the same as the XBT but
it also can record conductivity, and can be used to find salinity. The
collection of this information from the same locations, on each passing
will create a sample size that can be examined for trends in the
temperature and salinity at different depths, and information about
stratification and currents in the Drake Passage.(Picture above of Jared
Crenshaw deploying XBT and Twilight at 4a.m.)

We dropped our second XBT in 3859 meters at 3:49 a.m. From its
readings we saw some fluctuations in temperature between 400 and 800
meters. The temperature did not stay constant as the device sank. Did
we cross over mixed water or an area with possible stratification? We
also observed fluctuations in the first 100 meters between 5 a.m. - 6
a.m. Any speculation as to what caused these?

My science shift started at 3 a.m. this morning and by the end of my
shift at 6 a.m. the sun was rising. This early morning shift will help
me prepare for my 12-hr shift, 6 p.m. to 6 a.m. once we reach the
Antarctic Continent.

-David Sybert