Southern Ocean Iron Experiment (SOFeX) Cruise
January 5 - February 26, 2002
R/V Revelle Log Entry: Hello again. We’re about at the end of our journey. REVELLE comes alongside the dock in Lyttelton tomorrow morning at 0600. It’s been a long, but successful journey. One that really started 10 years ago when John Martin began planning for the first IRONEX experiment in the equatorial Pacific. That’s a long time for one idea like the Iron Hypothesis, which we’re testing, to be at the forefront of a science field. It’s quite a testimonial to the intellect of John that he created such a revolution in ocean biogeochemistry. We’re awfully sorry that he’s not here to share this time with us.
The weather has been cooperating nicely - kind of a grey sky, but the sea has been behind us for two days now. The captain says that is a first, the sea is usually right on your nose when coming home on this course. A last good omen for a very successful cruise.
I’ve included a chart of the ships track, through yesterday. Doesn’t look that far, but try driving to work at 22 kilometers/hour some day. If that seems slow, then try driving to work at 22 kilometers/hour for a week. POLAR STAR will go from McMurdo Station, to the South Patch and then to Chile - that will be a really long haul. At least it’s only one way.
Not much to do now, except pack up the last few odds and ends. This is the last update from REVELLE - tomorrow and the next day we’ll be busy all day with the unloading process. Hopefully that will get everything off the ship. Then it’s home, travel or just plain hunkering down for all the folks. Civilization will be a shock after 40 days with no strangers. Bye and thanks for the opportunity to write. It’s been a lot of fun.
Position: 66 degrees, 1 minutes South, 171 degrees, 2 minutes West
R/V Melville Log Entry: The weather for the most part has been lousy, completely overcast with dark gray lightening to a bright gray during mid-day. This makes color difficult to assess. I was joking to my colleagues that we now consider 90% overcast a sunny day. The last two days, however, we have seen the sun shine through. I mean big sun you could see and gorgeous blue sky. We are hoping for a satellite image of our experimental sites and what we need is at least one sunny square kilometer with no clouds at the time the satellite flies overhead (local noon). Since the experiment is now about 1000 square kilometers at the Southern Patch, I think the probability is pretty good. But let’s not wait and see what NASA thinks. As we look over the side at this Outside Patch station, we see a clear difference. Big, clear, blue, cold waters with tabular icebergs in the distance you could land an aircraft on and take off again. Whereas the Inside Patch stations are a definite green.
Why are clear skies important? A couple of reasons: with the increase in production we observe in the patch, we have seen both the growth of more phytoplankton and light within the mixed layer decrease. It may be that at depth, the bloom is becoming self shading and with the growth rates calculated by Mike Landry, we could see another doubling of yesterday’s biomass within the next two days. It would be important to understand how light limitation plays a role in Southern Ocean production at times of replete nutrients. Also, because there are still abundant nutrients and doublings in cell numbers occur about every three days, we may not see the end of this experiment while still onboard Melville. Even though Polar Star is due to arrive here tomorrow, we will have to rely upon our eyes in the sky to follow this experiment to completion. Thus simultaneous remote sensing and station occupation is necessary to quantify and calibrate the remote image. Sun shine on.
Over the last 24 hours the seas have been dropping. This allows greater imaging of ocean color in the absence of whitecaps and greater penetration of sunlight. It also allows for a much more comfortable ride and everyone slept like babies last night, all but those with a special mission:
The calm seas provided ideal conditions to search for the wandering MBARI drifter, D1. We were reaching a point in our schedule where three nights ship time had been devoted to the recovery of this drifter. This was to be our last. It had been sending all its sensor data but refusing to include its position. This was likely because it could not find a navigational satellite during its short wake up period. Our instructions were to reprogram the buoy over the radio (if we could make contact) and command it to turn full on and stay on for at least half an hour. This is somewhat risky because such a maneuver will rapidly drain the batteries and the buoy would go dead. Yet without a position we stood little chance of recovering it. We plotted its last known position (of over a week ago) and superimposed the drift pattern of its twin, D2, then we looked at the difference between D2 drift and the drift of the optical buoy deployed nearby, closed our eyes, flipped a coin and picked a point on the chart. (photo caption: Wendy Wang and the Wayward Widget. Wendy’s coordinates (and Mike’s keen eyesight) helped to recover the wayward MBARI drifter.)
At 0200 this morning, the seaman on watch, Mike Eubanks, spotted a blink in the distance using night vision goggles. He rallied more eyes. Sure enough there was a weak flicker about 7 kilometers off, a couple of points off to port, about the brightness of someone trying to strike a lighter under a rain coat. By 0300, the renegade drifter was tied tight to the winch on the fantail, standing upright to download the rest of its data. There would have been no way to find this had it not been very calm. We are hoping it stays this way.
Rosette recovery: Sequence showing recovery of TM Rosette from clear blue waters.
USCGC Polar Star Log Entry: What a difference a day makes! Our last report found us still struggling with a hasty set up and equipment woes in anticipation for our meeting with the Melville. As I head off to my cabin tonight, all systems are operational for detecting and studying the patch. At sea, you have no choice but to solve your problems as they come, and this crew and our group have quickly formed a team that was up to the challenge. Other issues and woes are likely to arrive, but for this moment, the seas are calm and all systems are GO.
I’m writing this report from the US Antarctic base in McMurdo where we are waiting for our ship to come in. For those of you unfamiliar with McMurdo, it is the largest base in Antarctica, with a peak of around 2000 inhabitants during the summer. We arrived along with the over winterers, hardy soles who will be isolated here for the next 9 months!
The first photo of the day shows scientific team members Leah Houghton and Laura Goldson working in our main lab on the SF6 system. For those following these web pages, you will know that SF6 is the inert tracer that was added at the start of the experiment along with iron, so that we could track the movements and dilution of our experimental patch in the ocean.
I've leaving an early morning wake up call for our rendezvous with the Melville. We made radio contact today, although the conversations were limited by static and poor reception on the other end of the radio. The plan is to conduct an initial in-patch sampling station to intercompare the experimental parameters measured on each ship. After a short 24 hours on station, the Melville leaves us on our own for the last week of the experiment. All eyes are fixed on the horizon for the upcoming rendezvous.
The last photo of the day shows me next to an important element of the Café Thorium research team- our espresso machine. My group takes our Italian espresso maker with us on all research expeditions, providing the perfect morning or late shift drink of choice. We are presently brewing a wonderful roast bean called "stout" from the C-1 Espresso bar and coffee roaster in Christchurch NZ. This coffee habit and our thorium-234 detectors make up the essential ingredients of the Café Thorium. Thorium-234, is a natural isotope that can be used to follow sinking particles, in this case flux of carbon to the ocean depths below the iron patch, but more on that in a later edition.
Till then - Ken Buesseler