Decadal Sea Surface Temperature Variability in the
Sub-Tropical South Pacific from 1726 to 1997 A.D.

Decadal Sea Surface Temperature Variability in the Sub-Tropical South Pacific from 1726 to 1997 A.D. Science v.290, pp1145-1148, 10 Nov 2000.

Braddock K. Linsley
University at Albany, State University of New York.
Gerard M. Wellington
University of Houston.
Daniel P. Schrag
Harvard University.

ABSTRACT:
We present a 271 year record of Sr/Ca variability in a coral from Rarotonga in the South Pacific gyre. Calibration with monthly sea surface temperature (SST) from satellite and ship measurements made in grid measuring 1 by 1 over the period from 1981 to 1997 indicates that this Sr/Ca record is an excellent proxy for SST. Comparison with SST from ship measurements made since 1950 in a grid measuring 5 by 5 also shows that the Sr/Ca data accurately record decadal changes in SST. The entire Sr/Ca record back to 1726 shows a distinct pattern of decadal variability with repeated decadal and interdecadal SST regime shifts greater than 0.75C. Comparison with decadal climate variability in the North Pacific as represented by the Pacific Decadal Oscillation index (1900-1997) indicates that several of the largest decadal-scale SST variations at Rarotonga are coherent with SST regime shifts in the North Pacific. This hemispheric symmetry suggests that tropical forcing may be an important factor in at least some of the decadal variability observed in the Pacific Ocean.

Download the Sr/Ca data and SST reconstruction and data description from this study from the WDC Paleo Archive.

To read or view the full study, please visit the Science website.
It was published in Science v.290, pp1145-1148, 10 Nov 2000.

Fig. 1 (above)
Comparison of monthly IGOSS sea surface temperature (SST) for the grid including Rarotonga (1x1; centered at 22S, 160W) and near-monthly Rarotonga coral Sr/Ca spanning the interval from 1981 to 1997. The linear least squares correlation between SST data and Rarotonga Sr/Ca has an r2= 0.75.

Fig. 2 (left)
Comparison of Rarotonga Sr/Ca calculated SST anomalies (deseasonalized) with values from a grid measuring 2 by 2 (CAC SST anomalies) and 5by 5 (OS SST anomalies ) for the Rarotonga region.
Fig. 3 (left)
(Upper curve): Near-monthly changes in calculated SST (C) spanning 1726 to 1997 using Rarotonga coral Sr/Ca and the regression relationship [SST (C) =140.55-12.15(Sr/Ca x 1000)] derived using data shown in Figure 1. (Lower curve) Oxygen isotope (d18O) measurements spanning the interval from 1726 to 1770 (see text).

Fig. 4 (below) Comparison of 8-year low-pass filtered versions of Rarotonga Sr/Ca calculated SST with mean removed (solid line) and the PDO index (dashed line). As defined by Mantua et al. (6), a positive phase of the PDO index corresponds to a El Nio mode and a negative phase corresponds to a La Nia mode. Solid arrows denote decadal cooling shifts of >0.75C at Rarotonga and open arrow indicates cooling trend possibly related to the Tambora eruption in April 1815.


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11 Nov 2000