Science & Technology

'Sea Gliders can help predict where dead zones will form'

Jack Barth, College of Earth, Ocean and Atmospheric Sciences, Oregon State University, spoke on how underwater Sea Gliders track dead zones

 
By Jack Barth
Last Updated: Tuesday 05 April 2016

How do these underwater gliders work?

Underwater gliders are vehicles that move through the ocean by changing their buoyancy relative to the water around them. The glider creates a slight increase (or decrease) in its overall volume, becoming lighter to move upward and heavier to move downward. The upward and downward motion is translated into forward motion by the wings of the glider. It is equipped with a range of sensors measuring temperature, salinity, dissolved oxygen, chlorophyll and light scatter. The glider's flight is controlled by a computer and a separate computer is tasked to collect the scientific data. The glider surfaces at a pre-set interval, typically several hours, and sends its GPS location and a subset of the ocean data back to the shore via a satellite cell phone. We can pilot the glider and send it to areas where we want to monitor.

How do they help collect data and monitor hypoxic (oxygen-depleted) zones?

We fly the gliders from the sea surface to within about three metres of the sea floor, mapping out the distribution of dissolved oxygen from near the coast to over 80 km offshore. The sampling is repeated a couple of times per week so that we can see the evolving distribution of low oxygen zones.

What new insights have you gathered?

Using the underwater gliders we have been able to see beneath the waves on a continuous basis. Just as satellites give us a nearly continuous view of sea surface properties like water temperature and ocean colour, the gliders provide us a view of the water properties beneath the sea surface. By sending data back in near real time, we track what regions of the coasts are low in oxygen, where it might be unusually warm or cold or fresh or salty. These water properties have a strong effect on the marine ecosystem.

How does this information help manage hypoxia formation?

The gliders will provide underwater data that can be coupled with satellite surface data and combined with computer models of ocean circulation and biology. This system, combining observations and modelling, will yield better understanding and some predictive capability for knowing where hypoxic zones are forming, or may form.

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