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VERTIGO - Students & the “Twilight Zone”

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» Rationale

» Methodology

» Wider Implications

» Suitable For

» Training

» Related Links

» References

The "twilight zone" is named for the region of low light below the ocean's sun lit surface "euphotic" zone. It of course also refers to the mysterious & unknown, and processes in this depth region are some of the least well understood in ocean sciences. Plans are underway for combined geochemical and biological field studies of the transport and fate of particles between the surface ocean and the deeper twilight zone.

Open ended cylinders and cones have been used for decades to collect sinking particles in the ocean. These so-called "sediment traps" are generally either fixed to the bottom of the ocean on a mooring, or suspended from floating tethers.

We have recently developed and tested an improved sediment trap that is designed around a neutrally buoyant float. Since ocean particles sink slowly (10's-100's m/day) relative to ocean currents (km/day) it becomes extremely difficult to collect particles from a fixed or slowly moving platform- sort of like trying to use a rain gauge in a hurricane. The Neutrally Buoyant Sediment Trap (NBST) drifts with the currents, thus eliminating hydrodynamic effects which can lead to particle sorting and flux biases. Our NBST opens up a new window to study more accurately the rain of particles out of the upper ocean.

In addition to the NBST, the Café Thorium lab led by Dr. Buesseler is known for the use and development of novel radionuclide approaches to studying ocean processes, including particle transport.

Wider Implications
Whether balancing the global carbon cycle or understanding the transport of pollutants in the ocean, quantitative knowledge of the rates and controls on processes that transfer material from the surface ocean to depth are critical.

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Suitable For
those students with an undergraduate background in chemistry and biology with environmental interests, though new approaches to understanding particle cycling in the ocean may also originate from those with backgrounds in physical sciences and modelling. Field work will be essential and careful analytical skills in inorganic or isotopic methods are likely needed.

The project would provide training in chemical and radiochemical analyses. Students would learn about interdisciplinary factors that control ocean biogeochemical cycles. In addition, application of these results to issues of climate change, and global carbon and nutrient cycling are anticipated.

Related Links
» Neutrally Bouyant Sediment Traps a Success! A new way to catch the rain
» 2002 Ocean Sciences poster on Neutrally Bouyant Sediment traps

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Buesseler, K.O., Steinberg, D.K., Michaels, A.F., Johnson, R.J., Andrews, J.E., Valdes, J.R., and J.F. Price (2000). A comparison of the quantity and quality of material caught in a neutrally buoyant versus surface-tethered sediment trap (PDF). Deep-Sea Res I, 47, 277-294.

Buesseler, K.O. (1998). The de-coupling of production and particulate export in the surface ocean (PDF). Global Biogoechemical Cycles, 12 (2), 297-310.

Stanley, R. H. R. Stanley, K. O. Buesseler, S. J. Manganini, D. K. Steinberg, and J. R. Valdes (2002). A Comparison of Major and Minor Elemental Fluxes collected using Neutrally Buoyant and Surface-Tethered Traps (PDF), submitted to Deep-Sea Research-I.

Voyage to ocean's 'Twilight Zone'

The Christian Science Monitor
February 12, 2004

Valdez, J.R., Buesseler, K.O. and Price, J.F., A New Way to Catch the Rain (PDF). Oceanus Fall/Winter 1997.

Buesseler, K.O., Meauring the "F" in JGOFS? A New Way to Catch the Rain (PDF). U.S. JGOFS News 10,2 (1999).

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