Will there be a 14C minimum in the tropical Pacific in the 1990s
- Princeton Univ., NJ (United States)
14C distributions measured during GEOSECS showed large minima in bomb 14C levels in the tropical belts of the major ocean basins. Broecker et al. (1978, JGR, 83) attributed the minima to upwelling of deep water which was free of bomb 14C. Wyrtki (1981, JPO, 11) countered that heat budgets constrain the water upwelling the the equator to be from the upper themocline. Druffel (1987, JMR, 45) built a model of the Pacific upwelling system incorporating Wyrtki's description of the upwelling system. Druffel showed that the GEOSECS 14C minimum could be reproduced with upwelled upper thermocline water because bomb 14C levels were still relatively low in the tropical thermocline at the time of GEOSECS. Druffel went on to predict that mid latitude and tropical surface 14C levels would approach a common value before the 1990s and upper thermocline water masses acquired more bomb 14C and atmospheric 14C levels declined. By studying pre-bomb coral 14C records and a model simulation in Toggweiler et al. (1989, JGR, 94), I have found confirmation that some older and colder water upwells in the tropical Pacific. Upper thermocline (22-24C) water has about the same pre-bomb 14C content as pre-bomb surface waters and cannot generate a low 14C singal prior to the bomb test. The appearance of the oldest upwelled water in the coral data is correlated in time with the cold phase of the ENSO cycle. Most of the low 14C water moves southward into the South Pacific. I will argue that intensified upwelling during the cold phase of ENSO pulls up 12-14C water from the lower layers of the Equatorial Undercurrent. Upwelling from this layer may represent an important closure mechanism for mode waters formed in the subantarctic. A source of older water makes it certain that the tropical 14C minimum will persist through the 1990s and the remainder of the post-bomb era.
- OSTI ID:
- 6880284
- Report Number(s):
- CONF-9002174-; CODEN: EOSTAJ
- Journal Information:
- EOS, Transactions, American Geophysical Union; (United States), Vol. 71:2; Conference: Ocean sciences meeting, New Orleans, LA (United States), 12-16 Feb 1990; ISSN 0096-3941
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
CARBON 14
DISTRIBUTION
FALLOUT
HISTORICAL ASPECTS
NUCLEAR EXPLOSIONS
PACIFIC OCEAN
TROPICAL REGIONS
UPWELLING
EQUATOR
NUCLEAR WEAPONS
SIMULATION
SURFACE WATERS
WATER
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON ISOTOPES
EVEN-EVEN NUCLEI
EXPLOSIONS
HYDROGEN COMPOUNDS
ISOTOPES
LIGHT NUCLEI
NUCLEI
OXYGEN COMPOUNDS
RADIOISOTOPES
SEAS
WEAPONS
YEARS LIVING RADIOISOTOPES
540330* - Environment
Aquatic- Radioactive Materials Monitoring & Transport- (1990-)
450200 - Military Technology
Weaponry
& National Defense- Nuclear Explosions & Explosives