Abstract
The Pacific Decadal Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere variability on decadal time scales. While precipitation and river flow variability in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence variability (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and decadal variability of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the variability in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate variability.
Highlights
Understanding past climate variability and the historical occurrence of extreme weather events, such as tropical cyclones and floods, is critical when predicting the ecological consequences of future climate change as well as preparing for their impacts on human coastal settlements
The luminescence record presented here displayed the temporal variability of river runoff on Keppel reefs and how such variability is influenced by the strength of La Nina and significantly modulated by the negative phase of Pacific Decadal Oscillation (PDO)-Interdecadal Pacific Oscillation (IPO)
Because recent evidence indicates that the effects of climatic phenomena (i.e. El NinoSouthern Oscillation (ENSO) events) may vary spatially in the Great Barrier Reef (GBR) [33], the strong relationship between PDO and coral luminescence documented here suggests that the southern GBR is sensitive to the PDO influence
Summary
Understanding past climate variability and the historical occurrence of extreme weather events, such as tropical cyclones and floods, is critical when predicting the ecological consequences of future climate change as well as preparing for their impacts on human coastal settlements. The effects of the El NinoSouthern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) on Australian hydrological regimes are relatively well understood [1,2,3,4,5,6], the 2010–2011 La Nina event, one of the strongest on record [7], severely impacted human communities and coastal ecosystems along the Queensland coast of Australia. Comprehensive historical analyses of such extreme events are scarce because of the lack of long-term instrumental and proxy climate records [9,10,11,12]. Predictions of their frequency and intensity remain uncertain
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