Sunday, March 31, 2013

Nights on a research vessel

A research cruise is a twenty-four hour operation. Some instruments, like the SeaSoar, need constant supervision. This means the operators have to work in shifts around the clock. Other measurements have to be taken at a specific time of the day, and sometimes the schedule changes quickly and people need to arrange a spontaneous recovery of an instrument.
Night on deck of the SARMIENTO
Kintxo and Miquel check the APEX float before the deployment
Nonetheless there are moments to relax and enjoy the views of the deep blue ocean at day or gaze at the white moon reflecting of the black sea surface at night.
The nights on the vessel are impressive. The sky is usually clear and there is nothing around us that emits light, except for the ship. The perfect opportunity to sit on deck and watch the moon and stars while the ship gently rocks on the waves.Yesterday we had full moon and the views of the moon are simply fascinating at night.
The moon light causes a halo in the night sky

Thursday, March 28, 2013

Visitors on the open ocean


To meet other ships up close is rare on the open ocean. This made the rendezvous between the American ENDEAVOR and the Spanish SARMIENTO a very interesting change of the daily routine. Since SPURS is an international cooperation, the chief scientist Ray Schmitt, Chris Duncombe-Rae and Julian Schanze climbed in the zodiac and navigated to the SARMIENTO under the eyes of scientists and crew on deck, who were watching the ENDEAVOR up close while the visitors were approaching.
Watching the visitors
The guests are all SPURS veterans from the R/V KNORR cruise in September 2012 and everybody was eager to share initial results and discuss the further planning.
But first the guests were shown around the spacious SARMIENTO and introduced to the captain and officers. Over dinner and coffee the further approach for the mission was discussed.
While the ENDEAVOR will be busy with recovering and maintaining instruments until the weekend, we will start another SeaSoar deployment in hope to find a fresh intrusion like the one we saw on the Southern end of the first SeaSoar sections. This will provide an opportunity to deploy instruments from both ships and map the region around the feature. Helping us to understand how freshwater is carried into the region and eventually enhanced in salinity again, due to exchange of moisture to the atmosphere.

Sarmiento Update 13-03-27

From Chief Scientist Jordi Font:

Last night we started releasing Luca's drifters (#114956, 114955, 114905, 114906, and a triplet 114814-114952-114911). We deployed again ASIP near to WHOI mooring and are now steaming south towing SeaSoar according to the strategy agreed yesterday in the joint Sarmiento-Endeavor meeting. Find attached a figure with release positions and planned SeaSoar track.

The rest of drifters will be released in the forthcoming days, using the time intervals between ASIP deployments.

On Wednesday we also deployed an Apex float in 24.702 -38.146 to perform shallow cycles (200 m). It has not been notified to the Argo system as we intend to use it in short deployments. We will send its positions in order to be included in the overall SPURS positioning data set (even it only surfaces for a few minutes every 4 h). We plan to pick it up on Saturday, after ASIP for a joint deployment on Sunday in the low salinity area in the SE that we are now going to map.

You can see many pictures in our ICM blog (translated version)



Wednesday, March 27, 2013

Floating Tupperware

“Why did someone tie a garbage bag to a piece of Tupperware and an oversized Styrofoam doughnut?” some cruise ship passenger might ask if they pass by the SPURS area. 
Acceleration sensor from below (Photo: Anonymous)
There is no doubt that a lot of the instruments we deploy look quite strange. But in oceanography it is all about the inner values, the sensors that provide us with information to understand how the ocean works. In this case the garbage bag is a drogue, which ensures that the float attached to it follows the surface currents of the ocean. The Tupperware is a waterproof GPS antenna for exact position data and the doughnut is an acceleration sensor, which can be used to infer energy input into the ocean by the wind and waves. 
Simon Morisset prepares his surface drifters
The system was developed at LOCEAN in Paris and Simon Morisset takes care of the deployment on board.
There are lots of different autonomous platforms involved in the SPURS program. Surface Drifters of various kinds, profiling floats and gliders provide a great coverage of the area both in time and space independent of the ship.
Kintxo Salvador and Miquel Rosell prepare the drifter
On the SARMIENTO we deployed three additional types of autonomous instruments additionally to Simons surface drifters. One APEX float which profiles the water column and a different kind of surface drifter that measures gradients in the upper meter of the water, using three tightly spaced sensors that record salinity, temperature and pressure every second. Then there is also the ASIP (AirSeaInteractionProfiler), which measures turbulence in the upper ocean up to the surface.  More on this instrument later…

All these instruments need to be recovered after deployment. Which should usually not be to hard, since all the instruments send out precise positions via satellite. But the ocean is not a controlled lab environment and sometimes things can go wrong…
Then the odd looks can actually come in quite handy in order to locate a tiny instrument on the open ocean between waves and sun glint.

A Beautiful Day to be an Oceanographer

Pictures from Julian Schanze on the Endeavor, March 26, 2013

A critter crawling around in some sargassum

Flat calm and glassy seas


Graduate student Alec Bogdanoff returning the above-pictured sargassum to its home in the sea. Behind him are wavegliders being transported home. In front the tip of one of the recovered seagliders.

Endeavor Update 13-03-27

From Chief Scientist Ray Schmitt:

3/27/13 update from Endeavor:

Today the weather was perfect.  No wind, glassy smooth ocean, sunny but not hot, beautiful sunrise and sunset, then a full moon.  And there are hurricane force winds in a huge low pressure system far to  
the north. We certainly chose the right spot to do oceanography!

Today we recovered a wayward Seaglider (at breakfast), a mixed layer float (at lunch) and the wandering NOAA mooring (at dinner). Perfect conditions for finding small targets, for small boat operations, and easy recovery of all instruments.  Only downside was a few folks missing meals because of the timing of the recoveries, but nobody is going hungry on this ship, Archie serves up great food every day.

Tonight we will do Underway CTDs back to the north, then we will spend Wednesday collecting microstructure profiles near ASIP and the two micro-gliders Helo and Saul, which have been following ASIP as it is carried west of the WHOI mooring.

There was strong surface diurnal warming of about 4 degrees C, and a surface salinification of about 0.1 psu was indicated by the "Salinity Snake" rigged up by Julian Schanze (SSS>37.5).  Hopefully tomorrow will have similar conditions for the VMP work.

We also managed to collect a bit of Sargassum weed, and photograph some of the inhabitants.  Lots of Trichodesmium around as well, looking like sawdust on the water.

A great day to be an oceanographer!

Ray Schmitt

Tuesday, March 26, 2013

Endeavor Update 13-03-26

From Endeavor Chief Scientist Ray Schmitt,

Just a quick update from Endeavor. Yesterday we successfully released and redeployed the WHOI mooring.  Perfect weather and Jeff was great as always. Today we launched 5 gliders; the two micro gliders were put in near Brian Ward's ASIP from the Sarmiento. We also recovered two Wavegliders.

Tonight we are steaming south to recover a drifting Seaglider, the mixed layer float and the PICO North mooring. If all goes well with those recoveries on Tuesday, we should be back on-site Wednesday for PICO mooring servicing (Prawler replacement on PICO-East) and if possible, the redeploy of PICO-North.  And recovery of 2 more Seagliders and 1 waveglider.

And Jordi invited me for lunch on the Sarmiento Wed.  We will play up the international cooperation angle, and plan some further work.  They have been generating some nice Seasoar sections.

Weather has been good here so far, though there are hurricane-force winds forecast north of us.


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...

Friday, March 22, 2013

Endeavor Update 13-03-22

From Chief Scientist Ray Schmitt:

Endeavor Blog:  Going up the river of salt one more time.

As we slowly make our way toward the salinity maximum of the north Atlantic, there is not much aboard demanding immediate attention.  Ships move slowly across the face of the globe and it will take us over 8 days to get to our site.  Our instruments have been tested, and we tweak gear and get used to the ship.  And the pressure of proposals and reviews never leaves, so sometimes it feels like you never left the office.  We are just as reachable by email out here by needy editors as we are back home. 

Nonetheless, there is time to reminisce, and since I am the old guy on this cruise I have more to recall than anyone else.  I can claim seniority this trip on Endeavor, I rode on her in Narragansett Bay shortly after she was delivered in 1976.  Captain Rhett joined her in 1982, and we have sailed together a number of times; I had 4 cruises on Endeavor in 1982 alone.  The name Endeavor comes from a famous British ship used by Captain Cook in the discovery of Australia.  There is actually a piece of the stern post of Cook’s Endeavour mounted in the library and photos of the Space Shuttle Endeavor as well.  A great name for a vessel of exploration.  

Though small compared to the Knorr, and thus more lively, one always feels that she will come back from every roll.  I have been on her in some really nasty blows in the Gulf Stream, and she will be moving around like mad, but you always felt safe.  Fortunately at my age I don’t get seasick any more, and though the first few days were pretty rough, we are now under light wind conditions and Endeavor is cruising along nicely.  The sun is shining and we are under the subtropical high.  Though a remarkably large and intense low pressure system churns to our north, sending long swell our way, it is so much longer than the boat that we simply bob up and down and don’t roll too much.  The Captain headed south of our line at first to keep us out of the nastiest weather and it has paid off.  A small ship like this cannot make good speed if it’s getting pounded by the seas.  He and I trade tales about the old days, from weather to prior captains, ports and cruises, when I head up to the bridge to check the forecast.

But I also reminisce about what has brought me here.  For it really goes back to one of my first oceanographic cruises as a grad student in the early ‘70’s.  It was on the rusty old “Trident”, URI’s first ship.  The cruise was out of Barbados, and we steamed northeast toward the origin of the salinity maximum waters for a while then turned northwest and ended in Bermuda.  We were testing a new free-fall profiler of Tom Rossby’s and doing CTD casts.  That early profiler had lots of problems but we did see interesting stuff in the CTD casts that led to my first paper and much of my research over my whole career.

What we saw were some interesting steps in the temperature and salinity profiles.  At that time Melvin Stern at URI had recently shown how such steps could appear in the laboratory when the salinity gradient was strong and “salt fingers” formed to allow the salt to fall down through the water column.  Salt fingers depend on the fact that salt diffuses much more slowly than heat.  The warm salty water above can lose heat to the cold fresh water below if it “fingers” downward.  This makes it become cold, salty water which is heavier so it continues to sink.  It passes heat to fresher water which warms, becomes buoyant and rises.  Such small-scale “double diffusive” convection can have dramatic consequences for the larger-scale temperature and salinity structure of the ocean.  But we did not know much about that back then.  I found it fascinating and learned enough from Mel Stern to make some fundamental contributions to salt finger theory.  It was great to be in on the ground floor of a relatively new field.  A matter of being in the right place at the right time.  

Salt fingers had brought me back to Barbados a number of times.  Just east of that tropical island we find the largest vertical salt gradients in the ocean thermocline and the strongest “thermohaline staircases” ever observed.   For the thermohaline staircase is the fully formed expression of salt fingers in the ocean, where their amplitudes get large and strong vertical mixing ensues.  We had proved this a decade ago, with a deliberate tracer release experiment.  My WHOI colleague Jim Ledwell injected a passive chemical into the center of the staircase and was able to watch it spread in the vertical by sampling nine months later.  The salt finger mixing rate was ten times as high as it is in non-staircase regions, solid proof that fingers were an important ocean mixing process.  In a way, you can think of the staircases as like a series of water falls in the river of salt.  We are presently approaching the “headwaters” of this salt river, the place where it gets the saltiest, highest up in the water column.  The ocean circulation carries this high salinity water beneath the surface off to the southwest toward Barbados in a distinct plume we call the river of salt.  Each of the subtopical gyres has its own river of salt, and we study this one to learn about them all.

We were there just 6 months ago, when we started SPURS by deploying an impressive array of floats, gliders, moorings and drifters.  The structure of the headwaters surprised us in several ways.  The salinity maximum turned out to be a plateau, there was a highest salinity that was reached in one specific patch of surface water and it did not vary much within that patch. Outside this water the salinity would swing wildly up and down but once in the saltiest patch it tended to stay at a constant high value.  Another surprise was just how salty it was.  There is a global trend for salty areas to get saltier and fresh areas to get fresher, a consequence of the water cycle intensifying with global warming.  These ocean salinity trends are a foreboding warning of what may be in store for mankind as the globe continues to warm.  A dramatic intensification of the water cycle means more intense droughts and more extreme storms and floods.  Alarmingly, we found the salinity to be saltier than had ever been observed before in that region.  The waters we are entering are certainly the saltiest in the global open ocean, though marginal seas such as the Mediterranean and Red seas do have higher salt concentrations.  There is strong evaporation here and little rainfall, a sort of oceanic desert where water is leaving the surface of the ocean.  The salt stays behind and gives us the river of salt, the water enters the atmosphere to begin the global water cycle.  It is truly the point of origin for both the atmospheric water cycle and the oceanic salt cycle; a place that has fascinated me for decades.  A place where we hope to learn how to interpret what’s going on with our global water cycle.  And the water cycle is truly an oceanic phenomenon, the terrestrial water cycle that we depend on for civilization is actually just a small side show compared to the water cycle over the ocean.  Given the how unexplored the ocean is, we learn something new every cruise.  What will we learn this time?            -Ray Schmitt, 3/22/13