The hunt for additional sources of terrestrial palaeoclimate information in Australia is hindered, in part, by the scarcity of mainland tree species suitable for traditional dendrochronological analysis. However, the emergence of novel analytical techniques has raised the possibility of obtaining climate information from a much broader range of tree species. The presence of ring-like structures in grey mangroves (Avicennia marina) has stimulated interest in applying dendrochronology to mangroves, but the highly variable periodicity of the growth layers and their non-concentric arrangement means that they cannot be interpreted as growth rings. Radial sequences of mangrove xylem wood measurements may be temporally anchored using bomb-pulse radiocarbon dating in lieu of annual growth rings. This approach was utilised for the present study to prepare timeseries of xylem vessel anatomy and stable isotopic composition (δ¹⁸O, δ¹³C) from four mangrove stems in two adjacent riverine estuaries in New South Wales. Calendar year values were estimated from the irregularly spaced (non-annual) series using linear interpolation, allowing data from the four stems to be averaged to produce a mean series from 1962-2016.

Significant spearman correlations were found with rainfall, sea level and several El Niño Southern Oscillation indices (r=-0.26 to r=-0.48). The season of Autumn featured consistently among all significant proxy/climate correlations. Radial growth rates were negatively associated with δ¹³C anomalies; decreasing during periods of increased water use efficiency and moisture stress as inferred from the δ¹³C series. These insights provide evidence of the potential for grey mangroves to be utilised as a novel source of palaeoclimate data. Grey mangroves can live for over 1000 years and are ubiquitous on the Australian coasts. Therefore, with further research and methodological optimisation, this species may have potential to provide important information regarding pre-instrumental climate in regions previously thought to be devoid of suitable terrestrial palaeoclimate proxy archives.