Tuesday, October 5, 2010

Time and Motion

Almost home…
0700 EST
41° 29.558’N, 70° 40.751’ W
Winds: 8 knots
Sea Surface Temperature: 66°F

Something woke me from a deep sleep at 0500 EST. It was something we had not known for many days. It was stillness. We had been transiting through a gale for almost two days and suddenly all was calm. I walked up to the bridge and fixed upon a light slowly flashing far away through the fog. We were almost home, and the peaceful sounds of Van Morrison’s “Into the Mystic” began to play in my mind.

The sea fought us for two days. Winds exceeded 40 knots. Waves pushed us back. Periodically, we made 4 knots at best—moving only 4 nautical miles closer to home for every hour that three diesel electric engines hummed below the waterline. Pizza for dinner, two Meclizine for desert, and then quick preparations for a long nap. This included filling a water bottle (you don’t know how long you’ll want to stay in bed), grabbing a good book, and then stuffing extra blankets under the side of the mattress. The latter curls the bed and keeps you off the floor. It may reduce the startling sensation of falling out of bed, but it does not reduce the sensation of falling out of the sky. Of countless such experiences, three were particularly memorable. Laying in darkness, head to the bow, feet to the stern, I would try to visualize our ship from above and the seas that were shoving it. Were we crossing the swell at an angle? That would explain the roll associated with the pitch. Was the wavelength close to the length of the ship? That would explain the regular rise and fall of Atlantis. Were we headed straight into it? That would explain ferocity. There was comfort in predictable regularity, and I nearly drifted to sleep. Then we began to fall. Faster. Head first. We crashed into the trough and the hull rang explosively. A bomb could have detonated under the deck and I wouldn’t have known the difference. According to our third mate, Kami, the wave “was taller than the house. The bow went under, and it knocked the phones out of their cradles.” Three times.

We were able to grab one last multi-core before the transit, but had to forgo two stations. Such is the nature of oceanography. The gaps in our data, and ultimately in our knowledge, are frequently driven by the temperament of our Planet. But in the end, we successfully sampled the majority of our proposed stations and all of our high priority stations. It is hard to believe that so much has happened and 26 days have passed. Does this mean it is over? Not hardly. Our immediate future involves unloading the ship, storing and properly cataloguing our samples in the libraries at WHOI, paperwork, etc… It also involves taking a moment to thank the wonderful crew, to step off the gangway, and to look back on the incredible machine we called home for one month: Atlantis. Followed by properly unwinding, of course.

A new adventure awaits on land—one in which we read aloud the messages stored in our bottles.

Sunday, October 3, 2010

Many Hats

Station 18
0656 EST
37° 28.181’ N, 74° 14.403’ W
Winds:11.6 knots
Sea Surface Temperature: 71°F

Before leaving Station 17 yesterday, we completed 4 CTD casts, deployed a sediment trap array, and recovered cores from the bottom of the sea. Sunrise came as Maureen Soon of University of British Columbia, Joe Murray of WHOI, Atlantis' SSSG Alison Heater, and winch operator “Catfish” (not shown) worked together to bring the CTD safely back on deck (see photo). The sediment trap deployment (see second photo) was a bigger show, and required many more people on hand to do it safely. Scientists and crew worked together to build a 2 km long chain of glass ball floats (in protective yellow plasticmolding), wire, three sediments traps (large yellow funnels), and an anchor system. It is out there now and will remain hidden from the sun for one year. During that time, particles will quietly sink into each trap and collect into a bottle at it's base. An empty bottle will rotate into position every two weeks, thus separating 1 year’s worth of sinking particles into 24 discrete samples. Next year we will steam back to this station, place a speaker beneath the ubiquitous waves, broadcast an acoustic signal that releases the anchor and call the traps home. Hopefully.

Traps like ours are perhaps the most common means for long-term chemical analyses of sinking particles. However, particles sinking at an angle, like blowing rain, are less likely to enter the trap and can result in an underestimation of the sinking particle flux. This artifact can be constrained by a very clever system of geochemical tracers: Uranium and Thorium. Uranium-238 is a very long-lived (4.5 billion year half-life) radioactive isotope that decays to become the very short-lived “daughter” Thorium-234 (24 day half-life). While Uranium-238 is more-or-less uniformly dissolved throughout the ocean, Thorium-234 is very “sticky” and can be readily swept away by sinking particles. Therefore, we can infer particle fluxes based on variations in the concentration of Thorium-234 relative to Uranium-238 in the water column. This is one example of the variety of techniques that we are employing to understand our planet. It is also one example of what lured me into marine science—the opportunity to wear many hats.

As marine scientists, we must be chemists, biologists, and physicists. We engineer and machine our own instruments. We employ a variety of analyses, including those of the mathematical persuasion. And we better know a bowline from clove hitch. But we are only one part of the scientific endeavor on Atlantis. Look again at today’s photos. Scientists and crew don hard-hats, share their skills, and work together on the deck in spirited teamwork to get the job done.

For more hats, please visit the following links:
  • CafĂ© Thorium – Ken Buesseler’s radiochemistry group at WHOI
  • Atlantis crew member, Lance Wills, throws his second hat into the ring with these incredible photographs