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Non-stationary ENSO teleconnections in northeast Australia Since 1650 AD E. Hendy, M.K. Gagan and J. Lough

Non-stationary ENSO teleconnections in northeast Australia Since 1650 AD

E. Hendy, M.K. Gagan and J. Lough

A 373-year chronology for eight, multi-century, Porites coral cores was developed using cross-dating techniques adapted from dendrochronology. Characteristic patterns of distinct fluorescent lines within the coral skeletons were matched between coral cores from inshore and mid-shelf reefs in the central Great Barrier Reef, Australia. Skeleton-plots of fluorescent banding were produced for each core and combined into a master chronology back to AD 1615, which overcame dating difficulties caused by core and discontinuities. The master record provides a proxy for Burdekin River discharge and Queensland summer rainfall.

 

Climatic patterns in NE Australia associated with El Niño Southern Oscillation (ENSO) events varied during the 20th century. Instrumental records show that the links were strong prior to the 1920s and since the 1960s, but were non-existent from the 1920s to 1950s, when interannual rainfall variability was reduced. Using the fluorescence master record, we have examined links between climatic variation in NE Queensland since the mid-17th century and a published reconstruction of ENSO for the same period (NINO3, 1650-1980). Correlations between the two series mimic the periods of fluctuating links during the 20th century. Furthermore, the master record is significantly correlated with the NINO3 series from the mid-17th to late 18th centuries, suggesting that ENSO-related patterns were as dominant then as in recent decades. However, the relationship between ENSO activity and Queensland rainfall is weak from the 1800s to the 1870s, when both inter-decadal and interannual variability are low in the fluorescence master record. In summary, these results show that recent increases in ENSO variability and the strength of the effect of ENSO on NE Queensland rainfall are not confined to the modern period, but instead occurred regularly over the past several centuries. Such variability must, therefore, be a mode of 'natural' climate behaviour that needs to be understood.