down and up and down again

What’s under the surface? Obviously more water, but how warm and salty is it at different depths? Finding the answer to that simple question is more difficult than you might expect, and crucial to understand the dynamics that create currents, transport heat, affect biology, and disperse pollutants.

One way to measure temperature and salinity (and thus density) along a vertical line is to stop the ship and lower a CTD rosette, (see previous post), which takes about 30 min to set-up, lower to 200 m,  and retrieve.

Another way is to drop a streamlined instrument package to the same depth and reel it back up in under 3 minutes, while the ship moves at up to 4 knots, and then continuously repeat, getting the data in real-time while moving across the ocean.

The fastCTD system was developed at the Scripps Institution of Oceanography, and has been deployed on research vessels across the world’s oceans. With this automated instrument (one of 2 units currently operating) we observed the evolution of the Bay of Bengal’s upper ocean under the onset of the monsoon winds & rains. The profiler made over 6000 trips from the surface to 200 m depth and back! And for the first time, it recorded chlorophyl fluorescence and particulate backscatter along the profiles, offering new insights into the biological communities and their distributions.

Find out more at

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