Abstract:
[Summary from the online data description
ftp://ftp.ngdc.noaa.gov/paleo/coral/west_pacific/readme_maiana.txt]
This data set is a 155-year ENSO reconstruction from a central
tropical Pacific coral that provides new evidence for long-term
changes in the regional mean climate and its variability. A gradual
transition in the early 20th century and the
... abrupt change in 1976,
both towards warmer/wetter conditions, co-occur with changes in
variability. In the mid-late 19th century, cooler/drier background
conditions coincided with prominent decadal variability; in the early
20th century, shorter-period (~2.9 years) variability
intensified. After 1920, variability weakens and becomes focused at
interannual time scales; with the shift in 1976, variability with a
period of about 4 years becomes prominent. Our results suggest that
variability in the tropical Pacific is linked to the region's mean
climate, and that changes in both have occurred during periods of
natural as well as anthropogenic climate forcing.
Sampling and isotopic analysis: Cores (8.5 cm diameter) drilled from
living coral colonies were slabbed and X-rayed to identify annual
density bands and optimal sampling transects. Samples were drilled
along the growth axis continuously at 1mm resolution. Stable isotopic
analysis (d18O and d13C) of powdered samples was performed on a
Micromass Optima with Isocarb automated preparation system at the
University of Colorado's Institute for Arctic and Alpine Research.
Analytical precision is =10.08 d18O and =10.05 d13C. The Maiana record
is continuous except for a gap from 1901-1905, which we bridged
through straight forward comparison and splicing of data from a coral
record from nearby Tarawa Atoll. 
