Tree Rings Show Recent High Summer-Autumn Precipitation in Northwest Australia Is Unprecedented within the Last Two Centuries

Abstract

An understanding of past hydroclimatic variability is critical to resolving the significance of recent recorded trends in Australian precipitation and informing climate models. Our aim was to reconstruct past hydroclimatic variability in semi-arid northwest Australia to provide a longer context within which to examine a recent period of unusually high summer-autumn precipitation. We developed a 210-year ring-width chronology from Callitris columellaris, which was highly correlated with summer-autumn (Dec–May) precipitation (r = 0.81; 1910–2011; p < 0.0001) and autumn (Mar–May) self-calibrating Palmer drought severity index (scPDSI, r = 0.73; 1910–2011; p < 0.0001) across semi-arid northwest Australia. A linear regression model was used to reconstruct precipitation and explained 66% of the variance in observed summer-autumn precipitation. Our reconstruction reveals inter-annual to multi-decadal scale variation in hydroclimate of the region during the last 210 years, typically showing periods of below average precipitation extending from one to three decades and periods of above average precipitation, which were often less than a decade. Our results demonstrate that the last two decades (1995–2012) have been unusually wet (average summer-autumn precipitation of 310 mm) compared to the previous two centuries (average summer-autumn precipitation of 229 mm), coinciding with both an anomalously high frequency and intensity of tropical cyclones in northwest Australia and the dominance of the positive phase of the Southern Annular Mode.

Living on a flammable planet: interdisciplinary, cross-scalar and varied cultural lessons, prospects and challenges

“…Continuing threats to aboriginal livelihoods make the region increasingly vulnerable to extensive wildfires in the face of climate change, which is causing both increased rainfall and greater interannual variability [75], both of which enhance the risk of extreme fire events [76,77].…”

Evidence for climate‐driven synchrony of marine and terrestrial ecosystems in northwest Australia

“…Additionally, growth chronologies derived from taxa that are sensitive to climate variations can be utilized to reconstruct past patterns of climate. In Australia, long‐term (multi‐decadal) growth records from trees and corals have been used to extend records of rainfall (e.g., Cullen & Grierson, ; Lough, ; O'Donnell et al ., ) and SST (Hendy et al ., ; Zinke et al ., , ) to times prior to instrumental records. Where connections between ocean and atmospheric processes lead to synchronous growth responses among marine and terrestrial taxa, multiproxy reconstructions of broad‐scale climate phenomena can be developed.…”

“…Long‐term growth chronologies have already been developed from trees (O'Donnell et al ., ), corals (Cooper et al ., ), and fish (Ong et al ., ) in this region, providing an opportunity to investigate linked biological responses to climate patterns across taxa and ecosystems. These earlier studies have revealed that growth of trees in NW Australia show a strong positive response to rainfall because water is a limiting resource (O'Donnell et al ., ).…”

“…Long‐term growth chronologies have already been developed from trees (O'Donnell et al ., ), corals (Cooper et al ., ), and fish (Ong et al ., ) in this region, providing an opportunity to investigate linked biological responses to climate patterns across taxa and ecosystems. These earlier studies have revealed that growth of trees in NW Australia show a strong positive response to rainfall because water is a limiting resource (O'Donnell et al ., ). Similarly, coral growth is influenced by regional changes in SST that affect calcification rates (Cooper et al ., ), while adult fish respond to changes in SST and sea surface salinity (SSS) because of changes in metabolism rates, osmoregulation, or food conversion efficiencies (Ong et al ., ).…”

Introduction to the special issue: historical and projected climatic changes to Australian natural hazards

“…Christensen et al 2013;Hartmann et al 2013) Bushfires: Shifts in SAM combined with shifts in larger scale drivers contribute to rainfall decreases across southern Australia, which directly and indirectly affect the moisture content of bushfire fuels (Hendon et al 2014;O'Donnell et al 2015) Heatwaves: Likelihood of extreme temperatures increases during negative phases (Marshall et al 2013;Min et al 2013); relationships with summertime heatwaves are less clear . Frost: During SAM positive phases, a poleward contraction of the mid-latitude storm track resulting in drier more stable atmospheric conditions interspersed by anomalous cold air advection from the poles during anomalously strong ridging high pressure activity (Cai and Cowan 2006;Frederiksen and Frederiksen 2007;Hope et al 2006;Risbey et al 2009a).…”