37° 28.181’ N, 74° 14.403’ W
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:
- Café Thorium – Ken Buesseler’s radiochemistry group at WHOI
- Atlantis crew member, Lance Wills, throws his second hat into the ring with these incredible photographs