Southern Ocean Iron Experiment (SOFeX) Cruise
January 19, 2002: Day 15
R/V Revelle: -55 50.385,-171 53.0256
R/V Melville: 44 degrees, 45 minutes South, 174 degrees, 19 minutes East
R/V Revelle Log Entry: The ship and drifters are just to the south of the patch at this time. We made a map of SF6 distributions during last nights SeaSoar survey and it looks like this with Drifter 2 at 0, 0 on the map.Weve done several sampling stations in the core of the patch. Today, weve been working in the area of highest SF6 concentration, which is the red blob on the map.
Chlorophyll continues to increase. Whos growing? Sue Brown is collecting samples from the Rosette sampler and then using a microscopic image analysis system to look at the phytoplankton.A phytoplankton that she doesnt recognize, about 15 mm in diameter, accounts for much of the increase in biomass. It may be a mixotrophic dinoflagellate - this is a plankter that can both photosynthesize and also prey on other phytoplankton.Hmmm.
The iron concentrations in the patch are just what we expected (this is also a thumbnail, so click on it to get a larger image).We increased the concentration about 1 nanomole/liter above the background after the first addition in the mixed layer.But Ginger and Zanna are now having a hard time measuring background iron (about 0.1 nM) because there is so much iron fertilizer sloshing around on the ship. Well have to get that cleaned up before we get to the South Patch area in a few days.
Meanwhile, were just finishing up a MLVS large volume pump cast and then a few other odds and ends before we leave here for the South Patch area around midnight. One of the fun things about being an oceanographer is getting to run some of the large cranes and winches on board ship. Not so fun when its cold, though..Phoebe Lam has to stand outside for 3 to 4 hours at a time to run the MLVS winch when these samples are collected.Oh well - she got a free trip to New Zealand and an ocean cruise.
Bye for now.
- Ken J.
R/V Melville Log Entry: After five days of loading tons of equipment onto her decks and into her holds and laboratories, modification of her equipment, re-supply of fuel, oil, water and food, the Research Vessel Melville sailed from Lyttelton Harbor under fair skies and calm seas, to meet her sister in the Southern Ocean. No more trips to the hardware store, no more long distance calls to loved ones, no more last minute repairs to equipment. The gap between the ship and the dock grew until the land was out of sight and all that was left was the gap. It is a largeness that is the ocean and the mysteries that she conceals that we intend to unravel in some ways. Now begins another adventure in which we all will play a part. So begins the second leg of the SOFeX cruise.
We seek to develop a mechanistic understanding of the processes that control the productivity of the Southern Ocean waters, the largest body of water containing un-utilized algal nutrients. We hypothesize that the factors which enable phytoplankton to utilize these nutrients will bear directly on climate change. Why? Because as these tiny phytoplankton grow, they take up carbon dioxide from the surrounding waters. The gasses in the water in turn equilibrates with the atmosphere.Thus phytoplankton growth in the oceans controls atmospheric carbon dioxide and in turn, global warming. There is strong evidence that Antarctic production has been linked to glacial/interglacial climate transitions in the past. But why are there such high levels of un-utilized nutrients in the Southern Ocean? Several factors contribute to this phenomenon including darkness in winter and extremely cold waters, yet even with 24 hour sunlight in the summertime, nutrients remain. We believe the missing ingredient is iron and have devised an experiment to test this hypothesis.
Our sister ship, Revelle, left this same port about two weeks ago to lay the ground work for these experiments on what is ultimately to be a three ship operation including the R/V Revelle, R/V Melville and the Research Ice Breaker, Polar Star.Over the last few days, scientists on Revelle have been adding trace quantities of iron to an area of the Southern Ocean, quantities that are designed to mimic those of the last ice age.What will happen in todays oceans and what this will tell us about the ice age oceans are the topics of our study. As Revelle steams away to another enrichment site, Melville will follow, thus extending our observations of the experimental areas and complimenting the studies aboard both vessels.