Tuesday, April 9, 2013

At the head of De Soto Canyon

The SailBuoy is now approaching the waypoint at the head of the De Soto Canyon. This past week, she finally made very good ground after a long period struggling against strong and facing winds. 

Now comes the moment to decide what the plan is for the coming weeks, and several options are being considered. 

The first is to go southeast to map the location of the Mississippi River plume. The plume can significantly impact the location of a surface oil spill, as researched and explained by Deep-C colleague Dr. Villy Kourafalou at  Rosenstiel School of Marine and Atmospheric Science at the University of Miami (Did the Mississippi River plume influence the surface spreading of the Deepwater Horizon oil spill patch?). However this would involve navigation in an area with very high ship traffic and where oil platform are numerous (see below). 

Oil rigs in the Gulf of Mexico.  Illustration by Nico Wienders
Another option is to remain in the less frequented eastern side of the Canyon to conduct more sampling and get more evidence of upwelling conditions. We work closely with the numeral modelers in order to produce the most suitable data set that can assist them in validating predictions. In-situ data (acquired in the place where it occurs) are pretty sparse for the De Soto Canyon area. Modelers need to compare their real-time model outputs with actual data to ensure there is no drift or difference between the fields they produce and, for instance, the data collected by the SailBuoy. This can easily be done using the Deep-C Atlas Map Viewer by superimposing different layers. And a third option for us is to command the buoy to stay at a fixed location in order to study the variations with time of the recorded oceanographic parameters.  

Regardless of which option we choose (and I will let you know in my next blog post), the buoy has now been in the water for almost a month, and this alone can be considered a success!

The SailBuoy can be equipped with a wide range of sensors. Of course, the more sensors,  the greater the cost of operating the buoy.  Electric consumption also increases with the number of captors/measurements and satellite transmissions (the SailBuoy can be equipped with solar panels, but the current mission is relying on batteries to power the sensors) 

For this mission, we installed highly accurate sensors that measure temperature, salinity, and oxygen concentration. Water temperature and salinity are tied to interactions with the atmosphere (heating, cooling, precipitation, evaporation) and have an effect on the density of water: warmer water is lighter, saltier water is heavier. The existence of these density differences is one of the mechanisms that contribute to movement in the ocean. Other forcing mechanisms include, for instance, the wind, the tides, earthquakes, and tsunamis. The sensor we are using on the SailBuoy to measure temperature and salinity is the new G-CTD, developed by the Neil Brown company. 

Sea Surface Temperature (ºC) in the North Atlantic
as seen via a 1/36 º numerical simulation
and showing the warm Gulf Stream.
Illustration by Nico Wienders
It's important to note that temperature and salinity can also be “advected" (which means transported by currents or eddies) in the ocean. Consider, for instance, the warm Gulf Stream. 

Oxygen concentration is also influenced by interaction with the atmosphere, as well as by biological consumption and chemical reactions.  In some ways, oxygen concentration can inform about the “age" of a water mass. However, oxygen concentration has no influence on the water density. 

Posted by:

Dr. Nico Wienders
Florida State University

1 comment:

  1. Very cool! Looking forward to hearing more about it...