By Bethany

Back in June of 2013, I sailed across the Great Australian Bight (the area of ocean below Australia) on the RV Southern Surveyor. One cold and windy night, myself and several other scientists scrambled out onto the deck with an expensive, large, yellow, plastic float. We threw released it over the side of the boat and watched it as it disappeared into the night.

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A daytime Argo float deployment

As one of 5000 Argo floats that scientists have released over board, it provides a way for us to continually monitor the oceans and send the data back to scientists on a regular basis via satellite. Here is a quick video which gives an overview of how Argo floats measure the ocean.

 

Almost 1000 days later, I’m happy to say the float is still floating! This float has spent 2 years, 8 months and 23 days floating in the sea, drifting with the currents, being caught in eddies and taking observations of the ocean. Within that time it has travelled over 4889 kilometres around the Great Australian Bight.

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A satellite image of the trajectory for Argo float 5904242 . The boat icon represents the launch location and the red line represents 100 km.

It has surfaced 102 times (represented by the white dots on the following map) to transmit salinity, temperature and density data back to scientists via satellite.

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A closer look at an Argo float and another daytime deployment.

So what does the data look like? Here is the latest temperature and salinity data for float WMO 5904242 (data was retrieved from Coriolis Operational Oceanography).

Temperature Profile
 5904242_sec_temp

The temperature profile is typical of the ocean thermocline, with a decrease in temperature as depth (sea water pressure) increases. The cycles between summer and winter can easily be seen in the surface waters, as it is warmer over the summer months but only recently reached a maximum temperature of 21ºC.

 

Salinity Profile

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This data is representative of just one float but combining the data of all the floats, (currently ~3918 live floats) can give us an idea of the conditions of the world’s oceans.