A Seaglider that had spent 149 days exploring the secrets of the Coral Sea, was recovered by Australian Institute of Marine Science (AIMS) researchers near Jewell Reef, north-east of Lizard Island, recently.
During its five months travelling one of the planet's least explored ocean regions the Integrated Marine Observing System (IMOS) Seaglider made 768 dives to depths of up to a kilometre and travelled 2,977 kilometres. The voyage was managed and controlled from the opposite side of the continent by scientists working at the University of Western Australia's National Facility for Ocean Gliders. While at sea it measured a host of key ocean variables such as temperature, salinity, plankton productivity, water turbidity and dissolved oxygen.
Seagliders are autonomous vehicles designed to profile the water column by changing their buoyancy and are able to descend and ascend in a sawtooth pattern. Pitch and roll is controllable by movable internal ballast (the battery pack) and in conjunction with wings that allows them to steer while profiling across strong currents. Seagliders fix their positions via the Global Positioning System (GPS) when they surface and communicate with the onshore laboratory via Iridium satellite, relaying collected data and receiving any new commands from the scientists.
This project is funded by the additional money IMOS received through the Education Investment Fund (EIF) in the 2009 Federal Budget.
Leader of the AIMS team that will be analysing and interpreting the data obtained by the Seaglider, physical oceanographer, Craig Steinberg, said the Coral Sea is one of the most sparsely sampled marine environments. ‘There has been a huge data and knowledge gap there,' Mr Steinberg said. ‘Our ship operations only get us there to do profiles once or twice every year, whereas the Seaglider is continuously logging away. In comparison to the cost of sending a ship to do an equivalent survey it really is very economical. This one voyage by this Seaglider has produced more data than all of Australia's past research surveys put together in this remote marine region.'
"The recovery of the ocean glider will have numerous practical benefits for Australians" said Mr Steinberg, "The data gathered during this project will help us to better understand the El Niño and La Niña cycles that drive weather patterns in eastern Australia". The El Niño phenomenon is associated with drought conditions in eastern Australia while the La Niña phase that we are now experiencing is characterised by warmer Coral Sea waters leading to predictions of a wetter summer and increased tropical cyclone activity.
Of particular interest to the AIMS researchers is the existence of an immense layer of plant plankton that is found at a depth of 50 to 150 metres in the Coral Sea. One of the predictions of climate change is that this layer, which is an important food source, could become thinner if ocean temperatures continue to increase, with significant consequences for the productivity of the Coral Sea. The glider was able to undertake detailed mapping of this plankton layer and IMOS will seek to sustain these measurements to determine any trends.