Observations of buoyant and dense water plumes on continental shelf waters around Australia using ocean gliders

Oceanographic observations has been traditionally undertaken using ships but the emergence of autonomous ocean gliders have provided an alternative measurement platform to acquire high spatial and temporal resolution data even during periods of extreme weather conditions. These data sets enable researchers to discover physical processes as well as document the natural variability of the ocean and coastal ecosystems. The Australian Integrated Marine Observation System (IMOS) ocean glider facility has been in operation for over 16 years and have completed more than 350 glider missions around Australia. One of the major highlights of the program was the discovery of Dense Shelf Water Transport (DSWT) around Australia that occurs when the density of the inner shelf water is higher compared to offshore and is transported along the sea bed across the continental shelf as a near bed dense water plume. The ocean glider data revealed that dense water plumes on the Australian continental shelves were a regular occurrence particularly during autumn and winter months. The extensive glider measurements revealed that the wind speed and direction play an important roles in the DSWT in addition to the cross-shelf density gradient. In recent years, there have been many high rainfall events around Australia that allowed the gliders to sample a number of river plumes and associated fronts across the country. Each of the river plumes exhibited contrasting dynamics with vertically well mixed fronts to typical river plumes. The roll-rate of the ocean glider was used to define the different mixing processes in these plumes.