ENSO and Indian Ocean subtropical dipole variability is recorded in a coral record off southwest Madagascar for the period 1659 to 1995

Details ENSO and Indian Ocean subtropical dipole variability is recorded in a coral record off southwest Madagascar for the period 1659 to 1995 ENSO and Indian Ocean subtropical dipole variability is recorded in a coral record off southwest Madagascar for the period 1659 to 1995

Nov 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004e%26psl.228..177z&link_type=abstract

Earth and Planetary Science Letters, Volume 228, Issue 1-2, p. 177-194.

Mathematics

Logic

23

Corals, Oxygen Isotopes, Trace Elements, Paleoclimatology, Indian Ocean Subtropical Dipole Events, Enso

Scientific paper

The Ifaty coral record from off SW Madagascar provide a 336-year coral oxygen isotope record that is used to investigate the natural variability of the western Indian Ocean subtropical SST dipole and ENSO. The coral oxygen isotope record primarily reflects past sea-surface temperature (SST) variability on seasonal to multidecadal scales. To validate the SST reconstructions derived from oxygen isotopes, Sr/Ca ratios were obtained for selected time windows (1973 1995, 1863 1910, 1784 1809, 1688 1710). The period 1675 1760 was found to be the coolest period of the entire record with anomalies of 0.3 0.5 °C that includes the Late Maunder Minimum (1675 1710). The warmest periods, as indicated by our data, occur between 1880 and 1900 and the upper part of the Ifaty record (1973 1995).
We generated a time series of coral δ18O for different seasons of the year to investigate austral winter and summer SST variability that influences rainfall intensity over southern Africa. Winter coral δ18O is coherent with winter SST on decadal and multidecadal time scales between 1854 and 1995. We suggest that the Ifaty winter time series provides a record of winter SST variability over the Mozambique Channel/Agulhas Current region over 336 years.
Strong Indian Ocean subtropical dipole events, occurring during austral summer, are displayed in the Ifaty record. The austral summer coral δ18O is coherent and in phase with ENSO indices on interannual time scales (2 4 years) between 1880 1920, 1930 1940 and after 1970. Our data indicate that the impact of ENSO on SW Indian Ocean SST and atmospheric circulation was also strong between 1680 1720 and 1760 1790, in agreement with other studies. We show evidence that these variations are caused by changes in the regional hydrologic balance. The results demonstrate that the impact of ENSO cycles in the region of the SW Indian Ocean has changed significantly since 1970 and relate to a warming of southwestern Indian Ocean surface waters altering the spatial signature of ENSO.

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