Monday, March 25, 2013

Slicing the Ocean

The deck of the SARMIENTO seems empty compared to other cruises, where usually anchors, sensors and other bulky equipment is piled up.
On the deck there are only two instruments strapped to the wooden floor. They look like well-fed yellow fish with a propeller at their tail.
These two instruments are called a SeaSoar and they are a key component to the survey we started 3 days ago. Once lowered into the water the instrument will be towed behind the ship at around 8 knots while it uses its wings to undulate between the surface and up to 400m taking continuous measurements of the water characteristics on its way.
SeaSoar deployment
These measurements include salinity, temperature, pressure, oxygen and fluorescence. The towed instrument provides much more profiles then a regular CTD sensor could achieve in the same time, since the traditional measurements require the ship to stop in order to lower the sensor.
Combining these measurements with the ships underway system, which collects temperature, salinity and fluorescence at the sea surface and maps ocean currents up to a depth of 600 meters, we collect a highly resolved data set of the upper water column.
The detailed pictures that we got after only a few days are truly fascinating. There is a sharply separated fresh feature in the upper 100 meters in the South and little pockets of subsurface salinity maxima detectable(see picture to the right).
Salinity from SeaSoar and Underway systems
In a few days the SARMIENTO will conduct another radiator-shaped survey further to the south to investigate meso-cale eddies that swirl in fresh and warm water from the south of the Sea Surface Salinity maximum and by that contribute to balance the loss of freshwater due to the excess evaporation in the subtropics.

Watching the sunset. while the SeaSoar is at work
Meanwhile the R/V ENDEAVOR has arrived in the SPURS area and will start working on servicing the moorings and autonomous platforms around it. On Wednesday the two ships are very close to each other near the central WHOI buoy and some folks might pay us a visit on the SARMIENTO, to discuss the plan for the next weeks and maybe have a ham sandwich or two...

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