Relative sea-level changes in southeastern Australia during the 19th and 20th centuries

Rates of global and regional sea-level rise between similar to 1850 and 1950 were high compared to those in preceding centuries. The cause of this sea-level acceleration remains uncertain, but it appears to be pronounced in a small set of relative sea-level proxy records from the Southern Hemisphere. Here we generate three new proxy-based relative sea-level reconstructions for southeastern Australia to investigate spatial patterns and causes of historical sea-level changes in the Tasman Sea. Palaeo sea-level estimates were determined using salt-marsh foraminifera as sea-level indicators. Records are underpinned by chronologies based on accelerator mass spectrometry C-14, radiogenic lead (Pb-210), stable lead isotopes and palynological analyses. Our reconstructions show that relative sea level rose by similar to 0.2-0.3 m over the last 200 years in southeastern Australia, and rates of sea-level rise were especially high over the first half of the 20(th) century. Based on modelled estimates of the contributing components to sea-level rise, we suggest that the episode of rapid sea-level rise was driven by barystatic contributions, but sterodynamic contributions were dominant by the mid-20(th) century. Significant spatial variability in relative sea level indicates that local to sub-regional drivers of sea level are also prominent. Our reconstructions significantly enhance our understanding of the spatiotemporal pattern of early 20(th) century sea-level rise in the region.