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Neptune's Whim

10/02/2011, 10:17 PM by Lollie Garay
Can you see what the ANACONDAS team saw?<br/><br/>Credit: Michael Oliveri
Can you see what the ANACONDAS team saw?
Photo Credit: Michael Oliveri

 

10/2/11

Between the plume and the ocean!

 A great story from Chief Tish today! She writes:

 “Neptune wagged his finger at me on Friday morning, and I learned something new in a place I thought we understood.  Here's the story:

 At Station 6 - early in the cruise, in the middle of the fresh water plume - we launched LOBO - an autonomous buoy that rises and falls through the water column as it measures the optical properties of the water and the particle concentrations (similar to last year's POGO).  It was doing a beautiful job of following the plume (we sampled near it again at Station 13), but then it got caught in the Brazil current and was headed south-southeast fast.... So even though we had big plans to sample the main plume in the north that day, we needed to chase it down and pick it up!"

 “ It was discouraging news since I knew we were running out of time and really wanted to sample the northern area –(maybe that's where the DDAs have been hiding).  But we needed to recover LOBO.  After sailing south about ten hours, we got to it during the wee dark hours on Friday morning.  With some very deft eagle eyes on the bridge and a very bright searchlight (LOBO was only visible by a bit of reflective tape on it's small mast), some extraordinary ship handling by the second mate, and a great "hook" by Troy Gunderson on deck, we brought it aboard about 3 AM.  Success!”

 “So then, we needed to take a few CTD profiles to calibrate the sensors.  Ok I thought… just a couple more hours here and then we would head back north.  Well... nothing is ever so easy!  The currents were ripping and Victoria was having a hard time getting the CTD to sample the depths she needed.  I was on the bridge feeling like time was slipping away. “

  “After the CTD cast, I was talking with Captain Curl about what might have been going on.  (Meanwhile, the sun had risen.) The captain points out to a very strong frontal feature that we had been sitting right on top of.  

"You know what "fronts" are in the atmosphere, right?  Places where two air masses come together and there are strong vertical wind velocities.   Well, the ocean has the same thing when two water masses converge.” 

 “Here we had found exactly where the river meets the sea!   (See images)  The first shows the first thing I saw, the difference in roughness.  The bridge could actually see the feature on the radar because of the difference in sea surface state.  The water to the right is clearly rougher than the water to the left. “

 “The second image is what I started to see better as I looked across it and the sun gave us more light.  There was blue water on the choppy side and green water on the smoother side.   An even closer look showed me that the green river water was coming right up against the blue ocean water.  A zigzag track across the front revealed salinity of 36.1 on one side and 33.8 on the other.  Wow!!!!!!!!!!!!!”

 “I ran around for a few minutes telling everyone to look outside and the ship literally started buzzing.  It was breakfast time, so the brainstorming began and we quickly called a PI meeting to discuss ideas about how to respond.   I suggested that we should split our station in half and try to sample both sides in quick succession.  It was then proposed that we should make this station one of our drift stations and put a sediment trap on either side - staying with the feature for at least one, maybe two days.   We decide to try that.  It was just too good of an opportunity to pass up!”

 "So, we have spent the past two days in a bit of a frenzy.  Dashing back and forth sampling "blue water" and then "green water."  Victoria even did a "Tow-Yo" CTD where she sent the CTD up and down (without firing bottles) as we slowly steamed across the front to look at the Temperature and Salinity and other things the instruments were measuring as it went up and down.  She was trying to see how the waters were mixing.”

 “But we also had to stay with the traps which got caught up in the same strong current that swept LOBO to this place.  As the traps drifted south-southeast, and some storms blew in that contributed to mixing, we slowly lost the sharp front and by yesterday evening, we decided to pull out the traps and head north again.  Overall, though, I think the station will provide a remarkable glimpse of how the fresh water mixes with the sea at the sharpest interface.” 

 “So, Neptune reminded me that even if you think you understand a part of the ocean, you can still be surprised and learn something new!”  

 “Feeling humble but energized, Tish”

 I responded to Tish by saying, “See, everything happens for a reason! No lost LOBO, no front!”

The ship was at station 27 when Tish sent this, but is now heading for another drift station in the north. (See newest sat image). More pieces to fit into the Plume Puzzle!!!

Lollie

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Question of the Day

  • Do the bacteria in the water make us sick?

    Only a few of them.  Bacteria are in every habitat on Earth, growing in soil, hot springs, radioactive waste, water, as well as in organic matter and the live bodies of plants and animals. Bacteria recycle nutrients, with many steps in nutrient cycles depending on these organisms, such as nitrogen fixation.