Date: Tue, 17 Mar 1998 14:09:11 -0500

Process 2 Report #4

	As we complete the final station of the final JGOFS Process cruise we are
exhausted and ready to head home.  We are definitely back in the "Furious
50's" as the pitching and pounding make it difficult to work or sleep while
underway.  Neptune tried to get in his last licks as winds kicked up and
were gusting over 45 kts when we pulled in the last CTD cast.
	Overall we accomplished the sampling goals of the cruise and completed nine
long stations for process measurements and 21 hydro stations.  We penetrated
further south (71degrees 18' S) than we had anticipated at the beginning of the
cruise.  No active bloom conditions were observed anywhere along the track,
though there was evidence (low pCO2, high biomass, slightly lower silicate)
of a past bloom south of 68.5 S.  But if large numbers of diatoms were
produced they were no longer in surface waters.  Fall is here and winter is
not far behind.
	After a stormy beginning, the primary productivity array was deployed and
recovered 6.5 times during the cruise and the deck of incubators had samples
cooking throughout the cruise.  Not all results are in, but productivity
rates are down substantially from Process 1 along the entire transect.
Underway sampling suggests little change in surface properties from our
southward traverse, but the surface temperature gradient across the front
from 61 to 60 S was even more linear as we steamed north.  Subsurface
boundaries are still sharp.
	The CTD and Trace-Metal Clean Rosettes continued operating throughout the
cruise, though we had to reterminate both wires a few times.  The rosettes
seem like remote-controlled mosquitoes that we send down into King Neptune's
depths to draw water from his veins at different strata.  Then like
vampires, the water catchers flock to the bottles to drain his precious
water to extract Neptune's secrets and ascertain his health.  We don't have
all the answers yet, but we have an abundance of good data to work on thanks
to the valiant efforts of too many people to name.  All (both ship and
science crew) have worked hard and are appreciated and we feel good about
what we have accomplished.  Speaking of Neptune, he has summoned many of us
to his court for some bizarre rituals that are to turn us into penguins for
having crossed the Antarctic Circle.  At least we'll have a chance to speak
our mind in song, dance and limericks at the court.
	On this final JGOFS Process cruise there are 3 participants who were on the
first JGOFS Process cruise in NABE; Bob Williams and I sailed with John
Marra as Chief Scientist.  I believe Sus Honjo was Chief Scientist on the
first trap mooring deployment cruise for NABE and is now doing "cleanup"
duty bringing in the trap moorings as Chief Scientist on the Palmer.
Looking back over the decade of JGOFS, some of the instruments and methods
used on this cruise are the same or similar to those used on the first JGOFS
cruise, but most instruments and techniques have been upgraded and many new
instruments have been added - optical instruments and shipboard flow
cytometers being the most conspicuous, and the most difficult to keep
operating.  There also seem to be more applications of both stable and
radioactive isotope labeling methods.  Underway sampling has increased with
each project, and more should be encouraged.  Precision and accuracy have
been improved on most measurements.  The biggest change I notice is in
computer power and the ability to display data fast enough for it to help in
our decision making during the cruise.  On the first Atlantis NABE cruise in
1989 there was the ship's computer, a CTD computer, one "Fat Mac" desk-top
model and lots of hand-held calculators.  By the 1992 EqPac cruises on the
Thompson there was a nearly equal number of scientists and computers, and
the shipboard network allowed a skilled computer person to access and plot
data during the cruise.  In the Arabian Sea the number of computers exceeded
the number of scientists on the Thompson.  Though I have not counted them on
the Revelle, I believe that, including the ship's computers, there are
nearly two computers for every person on the ship - many hooked to
instruments.  The CTD data are available minutes after a cast and can be
accessed and plotted by PCS, Macs or UNIX machines to guide future station
planning.  This has been critical for AESOPS since each cruise was able to
penetrate further south into unsampled waters as the ice melted.  We are
able to make color contour sections of CTD parameters and bottle data.  Of
course, the SeaSoar data are plotted in real time, creating a continuous
painting of multiple parameters in the water column, analogous to the way
geophysicists have obtained a continuous record of sub-bottom features
through seismic profiling for many decades.  The underway surface data are
available via the network and can be plotted to visualize the changes
underway.  Plots can be posted and their meaning debated and strategy
formulated for future sampling.  This is the first JGOFS project where we
have had SeaWiFs data available during a cruise.  Because of the cloud cover
in the Southern Ocean, images are obviously rare, but the two images we
received helped and encouraged us to push further south when some
indications were that we had reached the southern edge of the former bloom.
The images also suggested we should head SE to increase our chances of
encountering high-chlorophyll waters.
	SeaWiFs, SeaSoar and underway data have re-emphasized how patchy and
three-dimensional the ocean is, but there are also large regions of
similarity to which our rate measurements can be applied, and we have
covered a spectrum of conditions during this cruise.  Looking at the 1996
PMEL section of silicate along 170degreesW and our own section of silicate
values makes one realize that underway surface data don't tell the whole story.
North of the front the sub-mixed layer silicate values are just 5-10
umol/kg, whereas south of the front the sub-mixed layer values are 50-70
umol/kg.  Obviously it doesn't take much mixing south of the front to keep
surface silicate values high.  Still, the bloom apparently drew down
silicate in surface waters south of the front from 50 umol/kg during Survey
1 to less than 10 umol/kg during Survey 2, but the drawdown seemed to halt
at 66degreesS by the end of Survey 2 and did not move further south during 
Process 2.  Between 60 and 65 S the silicate values actually increased 
substantially between Survey 2 and Process 2 crossings, suggesting that mixing 
had entrained silicate from below the mixed layer at a rate faster than could be
taken up biologically.  The primary question is why did the bloom end?  The
days are still long, so there is plenty of light.  Micronutrient
limitations?  grazing pressure?  Another important question concerns the
fate of the carbon fixed in surface waters.  Honjo reports lots of material
in the traps at moorings 4 and 5.  Aggregates were seen in abundance at
depth in one POPS (Particle and Optics Profiling System) cast we made to
3000 m.  We have much to unravel.

Wilf Gardner
Chief Scientist