Present and future prolonged drought impacts on a large temperate embayment: Port Phillip Bay, Australia

Observations of a large temperate embayment in Victoria, Australia, reveal a sustained climatic shift that occurred in response to a prolonged drought in the region during 1997-2009. Historically, the bay is fresher than the ocean with fresh outflow to the sea. However, the drought has caused substantially elevated salinity and temperatures above adjacent oceanic waters. The bay's capacity to dilute and flush waste discharges to the ocean was also changed. Observed conditions have been numerically modelled with hydrodynamic and coupled lagrangian particle dispersion models to test differences in dispersion and exchange during historically fresher conditions and hypersaline bay scenarios. Further scenarios were tested for projected climate conditions which were similar to the recent drought responses in the bay. The models identified the effects on the circulation of the climatic shift including regions of increased vulnerability to extreme salinity in the bay, with some existing discharges concentrating in these regions of heightened vulnerability. Absolute salinity in the bay could reach critical levels of over 38 g kg(-1), in places, which may compromise bay ecology.