Southern Ocean GasEx Blog

Dispatches from the Southern Ocean Gas Exchange Experiment

From SuperSoaring to super boring

Posted by sogasex on March 21, 2008

By Burke Hales, Oregon State University

Together with colleagues Dave Hebert, Dale Hubbard, and Pete Strutton, I came on this cruise to generate three-dimensional snapshots of the carbon dynamics of the evolving tracer patch. We were going to do this using the ‘SuperSoar’, my evolving towed undulating vehicle that is in the early stages of hybridization between the Lamont Pumping SeaSoar and the OSU SuperSucker. This vehicle ‘soars’ up and down through the water column while being towed behind the ship by adjusting the angle of its wings. It carries a CTD sensor package that measures particulate carbon in the water, along with temperature, salinity, and depth. It also carries a high-pressure pump that sends seawater samples to the shipboard laboratory for fast chemical analyses of nutrients and CO2. For this cruise, we planned to deploy Dave’s TOMASI instrument, which tells us about turbulent mixing rates by making very high-frequency measurements of temperature and salinity fluctuations.

On March 6, shortly after the study site location was chosen, we deployed SuperSoar (see picture below) for a preliminary survey of the patch prior to injection. After about 7 hours of towing, the SuperSoar mysteriously stopped about halfway down one of its dives and started to come to the surface. With Dave right on my heels, I ran out on deck to see what was wrong, and found the winch torn loose from its rear securing hardware! We had gotten caught in some unseen underwater obstacle! As I raced back inside to ask the ship to stop before we broke the cable, Dave reported that the winch came slamming back down on deck before the ship slowed, as if SuperSoar had suddenly come loose from whatever it was caught on.

We managed to recover SuperSoar with no damage to the vehicle, but in the process the vehicle had started to tumble and the cable showed severe signs of twisting.

After getting everything on board and secured, we found that the hardware securing the winch to the deck had suffered some serious damage. Two ½” steel D-rings had broken under tension, with one almost pulling completely open. The 1” pad-eyes that secured the rear of the winch to the deck were bent over. (see picture below)

While we were incredibly unlucky to find something in this empty part of the ocean to run into, we were incredibly lucky that the cable didn’t part and send the SuperSoar on its way to the sea floor. Further examination of the cable showed that the Kevlar strength-member had suffered severe damage (see picture below). This cable is very specialized for the SuperSoar, and without it we are finished.

So, what do you do when the equipment you brought out to sea for a 42-day cruise gets irreparably damaged on about day 8? How do you justify two months away from the family? (see picture below) We refocused our efforts on measurement of the surface-water chemistry of the study region, providing detailed maps of surface-water CO2 levels (see pictures below). These show some significant variability in the study region that we might otherwise have missed. We’ll do some XBT temperature profiles to try to relate mixed-layer depths to our surface observations. We’ll do some low-speed, reduced-package deployments with only Dave’s TOMASI on the SuperSoar body to try to get a little bit of information about mixing rates at the base of the mixed layer.

And anything else we can think of to avoid having the rest of the cruise become super boring…

supersoar-scaled.jpg

SureSoar on the fantail

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Broken D-rings

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Damaged cable

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The rest of the Hales family

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mar11-14-survey-pco2-scaled.jpg

Detailed maps of surface water pCO2

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Katie Hales, the reason Burke is here.
10/10/1940 – 02/25/2008

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