| PALEOLIMNOLOGY |
Holocene changes in eastern tropical Pacific climate inferred from a Galápagos lake sediment record.
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Conroy, J.L.,Overpeck, J.T.,Cole, J.E.,Shanahan, T.,Steinitz-Kannan, M. 2008 Holocene changes in eastern tropical Pacific
climate inferred from a Galápagos lake sediment record. Quaternary Science Reviews Vol. 27, Issues 11-12, pp. 1166-1180.
| Data Coverage |
North: -.87 * South: -.87 |
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West: -89.45 * East: -89.45 |
Start Year: 9190 cal yr BP * End Year: -50 cal yr BP
Data: Please Cite Data Contributors!
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Summary: Paleoclimate records from the tropical Pacific suggest the early to
mid-Holocene was a period of reduced El Niño/Southern Oscillation (ENSO)
variability, with a transition to modern, increased ENSO frequency
occurring some time in the last few thousand years. However, the nature
and timing of this shift remains uncertain due to the discontinuous
nature and/or coarse resolution of many ENSO proxies, as well as a
lack of agreement between previously published records. A new,
continuous, climate record from El Junco Crater Lake in the Galápagos
Islands reveals several abrupt changes in lake level and precipitation
through the Holocene. Hydroclimatic model simulations suggest that
El Junco lake level responds sensitively to increases in precipitation
associated with El Niño events, rising during wet El Niño events and
falling during the intervening dry periods. Grain size data from El Junco
sediment cores indicate past lake level variability, likely associated
with changing seasonal precipitation and ENSO frequency. The grain size
data suggest increased precipitation intensity prior to 9000±120 cal
years BP, and after 4200±130 cal years BP, as well as a two-step increase
in precipitation at 3200±160 and 2000±100 cal years BP. Maximum Holocene
precipitation and inferred ENSO variability occurred between 2000±100 and
1500±70 cal years BP, during the same period that six other independent
proxy records suggest higher ENSO frequency and longer, stronger El Niño
events. Decreasing sediment carbon/nitrogen (C/N) ratios in El Junco
sediments indicate rising lake levels from the early Holocene to present,
corroborating the grain size data. The inferred increase in precipitation
at 4200±130 cal years BP and at 2000±100 cal years BP coincides with
decreasing Southwest Asian and East Asian Monsoon intensity, suggesting
tropical Pacific climate and the Asian monsoon were interconnected
systems at centennial to millennial timescales during the Holocene.
A weakening trend in the Asian monsoon and the trend toward wetter
conditions at El Junco also coincide with a trend toward cooler and drier
conditions inferred from Cariaco Basin sediment proxies from the
mid-Holocene to present, suggesting the migration of the Intertropical
Convergence Zone (ITCZ) likely influenced hydrological changes in both
the eastern tropical Pacific and the Asian Monsoon region during the Holocene.
More Info on Paleolimnology |
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Complete XML Record: noaa-lake-6109
(Last Revised: 2009-02-11 )
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