conditions when trying to simulate subduction
processes.
• Demonstration in a model simulation that eddy
transport is required to transport South Indian
subtropical gyre waters across the equator along
the western boundary.
• Use of CFCs to validate model parameterizations
of gas fluxes.
Biogeochemical Processes
The tracers provide a method for calculating rates of
biogeochemical fluxes that is independent of direct
biological measurements. Again the age information
from the CFCs is used to calculate rates for these
processes. (see Nitrogen Isotopes in the Ocean). The
following highlights some of the advances that have
come about in our understanding of biogeochemical
processes to which observations of CFCs have
contributed:
• Apparent oxygen utilization rates from the central
Arctic that are so high, they need to be balanced
by transport of high production water from over
the continental shelves.
• Quantification of moderate biological consumption and initially low oxygen concentrations
in the Arabian Sea are needed to maintain the low
oxygen layer.
• Calculation of denitrification rates for the Arabian
Sea and Bay of Bengal.
Conclusions
The advantage of oceanic tracers like CFCs is that
they can be used to provide timescale information for
oceanographic processes. Direct application of the
timescale information from the CFCs is used to calculate fluxes of atmospheric constituents, such as
CO 2 . The oceans have taken up a considerable portion of the anthropogenic CO 2 released to the atmosphere. A large part of the uptake involves water
mass formation in high latitudes. The rate at which
these waters are transported into the interior will
have an effect on the rate at which anthropogenic
CO 2 is taken up.
See also
Carbon Dioxide (CO 2 ) Cycle. Nitrogen Isotopes in
the Ocean. Tritium–Helium Dating.
Further Reading
Broecker WS and Peng T-H (1982) Tracers in the Sea.
Palisades,
NY:
Lamont-Doherty
Geological
Observatory, Columbia University.
Fine RA (1995) Tracers, time scales and the thermohaline
circulation: the lower limb in the North Atlantic Ocean.
Reviews of Geophysics 33: 1353--1365.
Rowland FS and Molina MJ (1994) Ozone depletion: 20
years after the alarm. Chemical & Engineering News
72: 8--13.
Schlosser P and Smethie WS (1994) Transient Tracers as a
Tool to Study Variability of Ocean Circulation. Natural
Climate Variability on Decadal-to-Century Time Scales,
pp. 274--288. Washington, DC: National Academic
Press.
Smethie WS, Fine RA, Putzka A, and Jones EP (2000)
Reaching the flow of North Atlantic Deep Water using
chlorofluorocarbons. Journal of Geophysical Research
105: 14 297--14 323.
Walker SJ, Weiss RF, and Salameth PK (2000)
Reconstructed histories of the annual mean atmospheric
mole fractions for the halocarbons CFC-11, CFC-12,
CFC-113 and carbon tetrachloride. Journal of
Geophysical Research 105: 14 285--14 296.
162 CFCS IN THE OCEAN
processes.
• Demonstration in a model simulation that eddy
transport is required to transport South Indian
subtropical gyre waters across the equator along
the western boundary.
• Use of CFCs to validate model parameterizations
of gas fluxes.
Biogeochemical Processes
The tracers provide a method for calculating rates of
biogeochemical fluxes that is independent of direct
biological measurements. Again the age information
from the CFCs is used to calculate rates for these
processes. (see Nitrogen Isotopes in the Ocean). The
following highlights some of the advances that have
come about in our understanding of biogeochemical
processes to which observations of CFCs have
contributed:
• Apparent oxygen utilization rates from the central
Arctic that are so high, they need to be balanced
by transport of high production water from over
the continental shelves.
• Quantification of moderate biological consumption and initially low oxygen concentrations
in the Arabian Sea are needed to maintain the low
oxygen layer.
• Calculation of denitrification rates for the Arabian
Sea and Bay of Bengal.
Conclusions
The advantage of oceanic tracers like CFCs is that
they can be used to provide timescale information for
oceanographic processes. Direct application of the
timescale information from the CFCs is used to calculate fluxes of atmospheric constituents, such as
CO 2 . The oceans have taken up a considerable portion of the anthropogenic CO 2 released to the atmosphere. A large part of the uptake involves water
mass formation in high latitudes. The rate at which
these waters are transported into the interior will
have an effect on the rate at which anthropogenic
CO 2 is taken up.
See also
Carbon Dioxide (CO 2 ) Cycle. Nitrogen Isotopes in
the Ocean. Tritium–Helium Dating.
Further Reading
Broecker WS and Peng T-H (1982) Tracers in the Sea.
Palisades,
NY:
Lamont-Doherty
Geological
Observatory, Columbia University.
Fine RA (1995) Tracers, time scales and the thermohaline
circulation: the lower limb in the North Atlantic Ocean.
Reviews of Geophysics 33: 1353--1365.
Rowland FS and Molina MJ (1994) Ozone depletion: 20
years after the alarm. Chemical & Engineering News
72: 8--13.
Schlosser P and Smethie WS (1994) Transient Tracers as a
Tool to Study Variability of Ocean Circulation. Natural
Climate Variability on Decadal-to-Century Time Scales,
pp. 274--288. Washington, DC: National Academic
Press.
Smethie WS, Fine RA, Putzka A, and Jones EP (2000)
Reaching the flow of North Atlantic Deep Water using
chlorofluorocarbons. Journal of Geophysical Research
105: 14 297--14 323.
Walker SJ, Weiss RF, and Salameth PK (2000)
Reconstructed histories of the annual mean atmospheric
mole fractions for the halocarbons CFC-11, CFC-12,
CFC-113 and carbon tetrachloride. Journal of
Geophysical Research 105: 14 285--14 296.
162 CFCS IN THE OCEAN