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Rationale
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.
Methodology
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.
Training
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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References
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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