year (MAT8333f8f3fc): paleoData_units: 'AD' has been replaced by 'yr AD'
year (MAT8333f8f3fc): paleoData_longName: '' has been replaced by 'AD'
d18O (Ocean2kHR_010): paleoData_longName: '' has been replaced by 'AD'

Abram, N.J., M.K. Gagan, J.E. Cole, W.S. Hantoro, and M. Mudelsee

Abram, N. J., Gagan, M. K., Cole, J. E., Hantoro, W. S. and Mudelsee, M.: Recent intensification of tropical climate variability in the Indian Ocean, Nature Geoscience, 1(12), 849–853, doi:10.1038/ngeo357, 2008.

Recent intensification of tropical climate variability in the Indian Ocean

Mantawai Islands, West Sumatra, Indonesia

Age models were developed using density banding visible in the X radiographs to identify the calendar year. X radiographs for these corals have been previously published [Goodkin, 2007; Goodkin et al., 2007, 2005]. Some error is expected within this age model because of years of very little or no growth, not visible on the X ray and also not clearly discernible in the seasonal cycles of Sr/Ca. While there is the potential for error generated by noise in the Sr/Ca or the annual band counting to result in the inappropriate addition of a year, the majority of age model error will arise because of missing years, generating a bias in which coral bands are assigned to artificially recent (younger) dates. For example, if the coral did not grow in 1950, 1949 would be inappropriately assigned the date 1950, and similarly for all coral years prior to 1950 (1781?1949). Such age model bias is suspected during the early to mid-1800s when growth rates were extremely slow for an extended period of time and hiatuses in growth may have occurred [Goodkin et al., 2005].

Finnigan MAT 253 isotope ratio mass spectrometer coupled to a Kiel III carbonate device at WHOI

However, the long-term trends in the raw d18O and Sr/Ca data provide a strong indication that the ocean surface waters near Bermuda were fresher during the LIA, even if we cannot quantitatively partition the temperature and salinity signals. Over the course of the 200-year record, long-term trends in mean annual and wintertime dOc (0.0003%/a and < 0.0001%/a, respectively) are effectively flat (Figures 4a and 4b). If dOc were purely a result of SST, and SST is increasing through time, a strong negative trend would be visible in the dOc records [McConnaughey, 1989a, 1989b].