March 13, 2001 to June 2, 2001
Monterey to Hawaii and back
May 27, 2001: Leg 5; Day 6
Ken Johnson writes: It’s Sunday morning and we’re rolling along at 9.5 knots towards Station 5 (29ºN, 141ºW) in light seas, a 10 knot wind and clear skies. We’ll arrive on station at about 2 this afternoon. The plan is to slow down a little after this station to conserve fuel. We’re running on two generators now. The Western Flyer has a diesel-electric propulsion system, four diesel engines (two big and two little) each turns a generator. This electricity is then sent to electric motors connected to a thruster in each hull. The diesels run at constant speed, which is very efficient, and the ships velocity is changed by turning on more generators or by controlling the speed of the electric motors. Right now we’re running on one big generator and one small generator. The big one is consuming fuel at about 45 gallons per hour and the small one is consuming fuel at about 17 gallons per hour. The small generator only adds one knot to our speed, but burns one quarter of the fuel. It will be turned off, since we don’t carry enough fuel to run both all the way. If all four generators were on, we could make 14 knots but we’d run out of fuel before we got home. Actually, the ship always carries a reserve to make sure that doesn’t happen, but we can’t use the reserve except in emergencies.
Moss Landing is at about 36N and 122W. We have four more stations with no more than two hours at each (we’ve beaten that easily so far). At 8.5 knots, when do you think we’ll arrive (hint: 60 nautical miles per degree latitude, but not longitude)?
So what is a day at sea like for a marine chemist, which is what most of the science party would call themselves. Our instruments are working 24 hours a day, 7 days a week and they need constant attention. Steve and Ginger are working 12 hour on, 12 hour off watches on the underway analytical instrumentation Steve gets 6 p.m. to 6 a.m. and Ginger gets the other half. This means Steve wakes up to dinner for breakfast and then has breakfast before bed. They are constantly busy tending the underway iron and aluminum machines, mixing chemical reagents and standards, fixing breakdowns and processing the data that is produced. Four times a day they collect and filter large volumes of water that we will analyze ashore for particulate metals.
Josh, Sara and I do the hydrocasts at each station and then Josh is busy for the next twelve hours or so analyzing the samples from the vertical profile for iron. If the stations are in the morning, he has a 12 hour day, if they’re latter, he has a very long day. Josh has produced four beautiful profiles so far. Fortunately we don’t have a station every day, so he has some recovery time. Sara (who is a marine biologist specializing in phytoplankton ecology) collects and processes biological samples from the flow through system and from the vertical profiles. She must work 24 hours a day, because she’s always in the lab when I cruise through. Sara’s results show that the maximum phytoplankton concentration is always at the minimum iron concentration. The plankton are depleting iron at the base of the sunlit zone (the euphotic zone) as they grow.
I baby sit all of the other underway instrumentation on board, including a Fast Repetition Rate Fluorometer, which measures the photosynthetic properties of plankton continuously. I also collect all the various data sets and collate them into a single product. We then make all kinds of plots, which we stick up on the wall of the wet lab. The fun part of the cruise is looking at these plots and arguing about what they mean. We have a stack of papers on iron and aluminum chemistry and we are constantly looking through them, trying to understand where our results are adding new insights, where they are supporting things that have been seen before, where we think other conclusions are wrong. We’ve written a computer model that simulates the chemical processes that occur when dust is deposited on the ocean and we’re tweaking the adjustable parameters in it to reproduce our results (tuning the model is the technical term). There’s a model developed at University of Hawaii called MADCOW (Model of Aluminum for Dust Calculation in Oceanic Waters). We’ll call ours RAGING BULL (Real-time assessment of Aluminum & iron Going Into the Northpacific Gyre, Biological Utilization at Low Levels).
Sara (who is a marine biologist specializing in phytoplankton ecology) collects and processes biological samples from the flow through system and from the vertical profiles. She must work 24 hours a day, because she’s always in the lab when I cruise through. Sara’s results show that the maximum phytoplankton concentration is always at the minimum iron concentration. The plankton are depleting iron at the base of the sunlit zone (the euphotic zone) as they grow.