Long-term modulation of the ENSO climatic cycle: Is the sun implicated
- Univ. of New Mexico, Albuquerque (United States)
Reconstruction of marine circulation from late Pleistocene varved and bioturbated sediments along the upper continental slope off California shows that conditions associated with El Nino circulation alternate with anti-El Nino (La Nina) conditions in cycles ranging from a decade to millennia. El Nino-like conditions are recognized in sediments as zones of bioturbation that have an increased concentration of terrigenous sediment and relatively low concentrations of biogenic silica and organic matter. Bioturbation occurs during episodes of higher concentration of dissolved oxygen. Conversely, anti-El Nino conditions are associated with varved sediments, which have an increased concentration of organic carbon and biogenic silica and are preserved during episode of low oxygen concentration. The shortest period is about a decade, twice the period in the instrumental record. Cycles of about 80 varve years also occur, and the strongest cycle is longer than 1000 varve years. Long term-cycles are also found in the historical El Nino record where episodes of frequent El Nino events ([approximately]0.4 events/yr) persist for decades and alternate with episodes of fewer El Nino events ([approximately]0.2 events/yr). The periods of alternation for cycles of more frequent and less frequent events in the historic record appears to be [approximately]50 and [approximately]100 years. It is suggested that the natural ENSO cycle (0.3+ events/yr) is being modulated to produce climatic cycles at lower frequencies. An association can be found between the number of El Nino events in long-term cycles and sunspot numbers, with more frequent El Nino events in long-term cycles and sunspont numbers, with more frequent El Nino events occurring during the Maunder and Dalton sunspot minima. However, direct solar modulation to produce long-period ENSO cycles appears to be ruled out by an extremely weak solar signal in the troposphere.
- OSTI ID:
- 6620911
- Report Number(s):
- CONF-9002174--
- Journal Information:
- EOS, Transactions, American Geophysical Union; (United States), Journal Name: EOS, Transactions, American Geophysical Union; (United States) Vol. 71:2; ISSN 0096-3941; ISSN EOSTAJ
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540310* -- Environment
Aquatic-- Basic Studies-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
CALIFORNIA
CARBON
CLIMATIC CHANGE
CONTINENTAL MARGIN
CONTINENTAL SLOPE
DEVELOPED COUNTRIES
EARTH ATMOSPHERE
ELEMENTS
GLOBAL ASPECTS
MAIN SEQUENCE STARS
MODULATION
NONMETALS
NORTH AMERICA
OCEANIC CIRCULATION
OXYGEN
PALEOCLIMATOLOGY
PALEONTOLOGY
SEDIMENTS
SOLAR ACTIVITY
SOUTHERN OSCILLATION
STARS
STARSPOTS
STELLAR ACTIVITY
SUN
SUNSPOTS
TROPOSPHERE
USA