Long-term stationarity of El Niño–Southern Oscillation teleconnections in southeastern Australia
The El Niño–Southern Oscillation (ENSO) phenomenon plays a large role in the modulation of Australian rainfall, particularly in the highly populated southeast. However, this influence is not stationary over time: weak ENSO teleconnections in Australia have been identified during 1920–1950, and palaeoclimate reconstructions indicate that a breakdown in global ENSO teleconnections may have also occurred in the early to mid-1800s. A lack of long-term instrumental data has prevented detailed examination of this intriguing earlier period. This study uses newly recovered instrumental rainfall observations to determine whether the weakening of ENSO teleconnections in the nineteenth century is apparent in eastern and southern southeastern Australia (SEA). Quantitative rainfall and rainday data from 1788 to 2012 are compared with three ENSO indices derived from palaeoclimate data. Statistical analysis suggests a weakening of the relationship between ENSO and SEA rainfall in the early nineteenth century data (~1835–1850), supporting results reported in previous global and regional studies based on palaeoclimate and documentary rainfall reconstructions. Possible causes of this weakening in teleconnection strength are then explored by examining a range of Southern Hemisphere circulation indices. The 1835–1850 period of low ENSO–SEA rainfall correlations appears to be characterised by a combination of reduced La Niña events and ENSO variance associated with a positive phase of the Interdecadal Pacific Oscillation, with the possible influence of a predominately negative phase of the Southern Annular Mode. However, current temporal and geographical data limitations prevent definitive conclusions from being drawn. Despite these caveats, this study illustrates the considerable value of historical instrumental climate data in assessing long-term variations in climate mode teleconnections, particularly in the data-poor Southern Hemisphere.
KeywordsHistorical climatology Palaeoclimatology Southeastern Australia Instrumental data El Niño–Southern Oscillation Teleconnections Southern Hemisphere
This study was conducted as part of the South Eastern Australian Recent Climate History (SEARCH) project, supported by the Australian Research Council (ARC) Linkage Project LP0990151. LA and DK were also supported by the ARC Centre of Excellence for Climate System Science, and JG acknowledges funding from ARC fellowship DE130100668. We thank Blair Trewin, Claire Fenby, Ailie Gallant and three anonymous reviewers for advice that helped improve this manuscript.
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