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Salinity Processes in the Upper Ocean Regional Study (SPURS): SPURS Epilogue (The First)

October 15th, 2012 by Maria-Jose Viñas

By Eric Lindstrom

“Ships at a distance have every man’s wish on board.” — Zora Neale Hurston

Actual spurs.

So, we are back in port in the Azores Islands of Portugal. Knorr 209-1 was a fabulous voyage and it did feel that we had many a man’s wish on board. Those included wishes for our data collection from all the scientists involved in SPURS and well wishes from all the family members of the expedition and finally the good wishes of you, my blog audience.

The Knorr SPURS science group.

Thank you all for following my SPURS adventure so far. The saga continues for another year. We have instruments in the water and more expeditions ahead (in March and September 2013). Each expedition will be slightly different in nature but overall working toward the SPURS goal of understanding the surface salinity maximum in the Atlantic and the water cycle on the planet. I’ll be going into a different mode of blogging now, to provide you updates on the science and the observations as the year goes along. With good fortune, I will get back to sea for the final leg of SPURS in September 2013. If you would like another voyage blog from the Sargasso Sea in 2013, let your voices be heard in the comments section below!

After several days of riding a lumpy swell from Tropical Storm Oscar, we were greeted by the magnificent sight of greenery and civilization at Ponta Delgada on the island of São Miguel.

Ponta Delgada’s water front.

Panorama of Ponta Delgada’s waterfront.

The Knorr in Ponta Delgada.

The expedition was a success scientifically.  We got our sensor web in the water for the coming year: three moorings, 25 Argo floats, 18 surface drifters, three Wavegliders, three Seagliders, and a Lagrangian Mixed Layer Float. We completed a wide variety of shipboard deployments: 764 Underway CTD casts, 100 CTD/LADCP Stations, 30 Vertical Microstructure Profiles, 33 AUV missions, three Slocum glider turbulence missions, and a full suite of continuous measurements including ocean velocity profiles, thermosalinograph and meteorology/fluxes. We accomplished the objectives we had laid out for us – deploy the sensor web (week 1), do a control volume survey around the moorings (week 2), and map a mesoscale ocean feature (week 3). We were able to squeeze in some extras, like a 24-hour time series in the saltiest water and pick up a glider from the French expedition in August.

The expedition was a success for NASA and WHOI.  We even caught the attention of the International Space Station and had a great 30-minute chat with Commander Sunita Williams about research in sea and space and the strong connections between the space program and oceanography.

The expedition was a success in interagency cooperation. SPURS is led by NASA, but has enormously important contributions from NSF, NOAA, and the Office of Naval Research.  It takes a village to put on a good oceanographic process study!

I created a “SPURS Illustrated Campaign Summary” from our Knorr expedition. I will make it available to all of you as part of a future post. There will also be movies available from the Space Station call and from the expedition, which are still in the editing process.

Your questions and comments on SPURS are always welcome. Use the comments section of any of the posts and I will get the message. Your interest and curiosity provides directions for future blogs and helps me put into words some of the technical aspects of SPURS that may not be fully understood.

Thanks you all for again following along on our Knorr SPURS expedition. There is much more to come, so stay tuned!

Salinity Processes in the Upper Ocean Regional Study (SPURS): Channel Fever

October 12th, 2012 by Maria-Jose Viñas

By Eric Lindstrom

Channel fever: an unusual excitement or restlessness common among a ship’s crew when the ship nears port after a voyage (The term probably refers to the English Channel, between southern England and northern France.)

Knorr-crew T-shirt for SPURS – there is no significance to the dinosaur as far as anyone knows.

Now that all the oceanography is done, it’s four days of steaming to the Azores. During that time there is still plenty to do. A shipping container is being prepared for freight to Woods Hole. People are comparing notes on their flights out of the Azores and taking guesses at what time we will be getting off the ship.

We are writing expedition reports (something your blogger has pretty well in hand!). I took over 2,000 pictures during the voyage and wrote 32 blog posts. I plan on finishing this trip with an epilogue as next posting. Then, after I return home, you will be able to access my presentation entitled “An Illustrated SPURS Campaign Summary,” which captures the entire expedition accomplishments in pictures. Remember too, if you have become a fan of SPURS, that there are more expeditions in 2013 and a sensor web in the water until next October. I will be blogging periodically to keep you up-to-date on developments and findings. For now, I need a rest from blogging. It feels like channel fever!

SPURS members writing reports.

Personal gear has to be packed and cabins cleaned. That leaves people with time to think about what they will be doing in the Azores or when they get home. People are laughing more and joking more. Sometimes, with all this activity, happiness emerges as channel fever.

Our bags are packed.

Does Julius have channel fever?

Maybe it’s the transformation of the ship – from being loaded down with gear to empty cleanliness. There are empty reels and baskets indicating our success at deploying moorings. The CTD master control station, hub of so much activity for the past weeks, is now quiet. Everywhere you look, it’s looking like its over. It’s enough to bring on channel fever.

The reels are empty now.

All the CTD stations are over.

We are taking stock at what we have done. We deployed three moorings, 100 CTD stations, 764 Underway CTD casts, 25 Argo floats, 18 surface drifters and a Lagrangian float. We left three Wavegliders and three Seagliders patrolling the seas near the moorings. The salinity field over a 120×120 mile piece of ocean was pretty well mapped. We have gigabytes of data to sift through and analyze. And we are pleased. We are weary. And we know when we see the Azores we are nearly home. That feels like channel fever!

We leave the lovely blue Sargasso Sea in our wake, but we can feel the harbor channel in Ponta Delgada, Azores in our future. We feel the accomplishment of the mission, and the promise of home. That is channel fever.

Salinity Processes in the Upper Ocean Regional Study (SPURS): Ocean Motion

October 11th, 2012 by Maria-Jose Viñas

By Eric Lindstrom

When on land, an oceanography brain usually associates the term ocean motion with the movement of seawater in the form of ocean currents.

Depictions of ocean surface currents derived from satellite data can be viewed at NASA’s OceanMotion.org web site.

However, when actually on the ocean, the biggest signal for our oceanography brains to cope with is the role of ocean motion in the pitch and roll of the ship (due to wind seas and swell). OK, so I am telling you that feelings matter. If you have ever been seasick, then you know what I am talking about!

So, if you spend 33 days on a small vessel at sea, you get a great appreciation of ship motion. There are actual six axes of motion of two kinds (lateral and rotational). Laterally there are surge (fore and aft), sway (port and starboard), and heave (up and down). Rotation also occurs around three axes that are more commonly discussed (maybe because we feel them more?). They are pitch (around port to starboard axis), roll (around bow to stern axis), and yaw (around the vertical axis). We can definitely feel all these motions but some do matter to our feelings more than others. Perhaps the most noticeable ones for land-loving creatures like humans are heave (the accelerating elevator feeling) and rotational motions largely absent in our daily lives (pitch and roll). Together, these can be combined into a kind of perfect storm of corkscrew-like motion that weakens the resolve of even veteran mariners. Lucky for us, the SPURS cruise has been pretty calm and no one has been suffering from seasickness.

By far the most noticeable and everyday motions on a ship are that of pitch and roll. Pitch is especially noticeable when navigating into a swell or into the wind. Going downwind or in the direction of the swell is much more gentle pitch-wise (sailors are wished good luck by offering them “fair winds and following seas”). Roll is especially diabolic when one is navigating nearly parallel with the troughs and crests of the swell. This is something you DO NOT do when the seas are large because you may very well roll over (not good; do not try this at home!). Faced with large seas, the safest course is to ride the weather facing into the wind and waves (and just suffer the horrible pitching).

Sorry to go on for so long about the ship motion, but its an ever present partner to our expedition and you deserve a share for sticking with us!

You may be wondering about the difference of wind seas and swell. Good question!  Swell and wind seas are both manifestations of surface gravity waves. Swell is caused by wind forcing of the ocean in some remote location. Wind seas are the jumble of more disorganized waves that come up directly under and within a wind event. There has been a good swell running in the SPURS region for the last two weeks due to Hurricane Nadine hundreds of miles away. On top of the swell, the wind waves cause whitecaps and noticeable roughness above wind speeds of about 10 miles per hour.

Well, on Knorr we are not out here to study wind waves (just feel them). I should get on to talking a little about ocean surface currents. Our main focus is the surface salinity and how it gets to be the way it is. Ocean currents moving patches of different salinity around is one key factor in accounting for salinity changes at any site in the ocean (we call this advection of salinity). The Ocean Motion web site produced for the NASA Physical Oceanography Program has a wealth of background information on ocean surface currents. Here in SPURS we believe there are only weak average currents (a year of moored measurements will determine that for sure), but that the wind-forced transient currents play an important role in the local water cycle (and surface salinity values). One obvious reason to think this is that the salinity maximum here is hundreds of miles north of the maximum in evaporation minus precipitation. The simplest explanation for this displacement is the northward movement of surface waters induced by the trade winds. On average, upper ocean waters forced by wind move 90 degrees to the right of the wind in the northern hemisphere so the easterlies of the trades give the ocean waters a push toward the north. This hypothesis will be tested by the SPURS observations over the coming year.

SPURS Argo float locations over time indicating flow at their parking depth of 3,300 ft. (Courtesy of Jessica Anderson.)

Out here it is extraordinarily difficult to fully appreciate the complexity of the currents around us in the upper ocean. The average current is small, but there are eddies and fronts with stronger flows around us that we observe sporadically as we move around from hour to hour.

Map of current vectors in the upper 167 feet (51m) along our track color coded by the surface salinity. (Courtesy of Phil Mele.)

We will only be able to make sense of our hour-to-hour estimates of ocean motion once we return to shore and can fully integrate the satellite and model information into the picture. We obtain details profiles of current vectors on each station but honestly have a tough time “connecting the dots” in real-time. It will take a good bit of analysis to understand the complex flow field.

Vertical variation of velocity vectors at three adjacent stations on the same day. (Courtesy of Julian Shanze.)

It feels a little like mapping Washington, D.C. in one day, from your car, driving around with a simple still camera. We get some great snapshots, but we can only place them in a larger context when be have full access to maps, satellite images, and historical records (stuff most people cannot examine in their car while driving around!)

As in rest of life, context is important in oceanography. We strive for it, but as with most things, the perspective of hindsight provides the best context. Feeling seasick is no exception! It’s so awful in the moment, and such a trifle in the glory of the entire expedition.

Salinity Processes in the Upper Ocean Regional Study (SPURS): How Do You Spell Physical Oceanography?

October 10th, 2012 by Maria-Jose Viñas

By Eric Lindstrom

How do you spell physical oceanography? I know my answer for that question! It’s easy: CTD.

CTD art in the blue Sargasso Sea.

CTD into the water.

For about the last 40 years, the mainstay of physical oceanography has been profiling the ocean with sensors for Conductivity, Temperature, and Depth (CTD). The SPURS cruise is no exception. These are key properties to derive salinity and the physical state of the seawater is described through the “Equation of State” which depends on temperature, salinity and depth.

During SPURS, we are doing CTD stations from four to six times per day (to  around 3,300 feet depth) and using an underway CTD as frequently as every 15 minutes (to about 1,300 ft). Computers aboard transform the raw sensor data into temperature, salinity, and depth information at regular levels (say every 3 feet) depending on the need. From there, it is relatively easy to use the equation of state to derive density and to estimate the geostrophic currents between the various CTD casts. Those are the currents caused by pressure variations resulting from the spatial density differences (like the winds between high and low pressure systems in the atmosphere). So CTD helps us unlock a major piece of ocean circulation, right there.

The CTD is the basic instrument embedded in most of our platforms – on gliders, moorings, autonomous vehicles, and our Knorr thermosalinograph. All use similar sensors in slightly different configurations. All the incoming data is converted to temperature and salinity data spread through space and time. Different CTDs on different platforms are specialized to measure different time and space scales of the temperature and salinity fields. So, some CTDs measure the microstructure at inches and smaller, and some better measure the variations over the full ocean depth. Some work best while moving rapidly through the water, while others are specialized for stationary measurements. Any way you cut it, you still spell physical oceanography with a CTD.

The underway CTD team.

Underway CTD unit clips to tip with 1,300 ft (400 m) of line.

Dropping the underway CTD over the stern.

Over the course of one SPURS expedition the number of CTD stations may number in the hundreds. And since we launch the underway CTD as often as possible as we go between stations, as many as a thousand underway CTD profiles are collected over a month at sea. The usual arrangement for CTD profiles is to mount the instrument inside a metal frame and pairing it with a rosette. On the rosette, one can mount Niskin bottles (http://en.wikipedia.org/wiki/Nansen_bottle ) for collecting water samples. The Niskin bottles are cocked open before the CTD cast and are tripped in sequence.  Samples are then extracted on deck for calibration of salinity (or any other purposes).

A top view of an open Niskin bottle.

A bottom view of an open Niskin bottle.

All in all, the CTD is THE instrument of SPURS and the mainstay of physical oceanography since the 1970s. It was used to map the properties of the global ocean in the World Ocean Circulation Experiment in the 1990’s. In SPURS it will provide us with an unprecedented view of the salinity variations here in the highest salinity region of the Atlantic Ocean.

Salinity Processes in the Upper Ocean Regional Study (SPURS): Hello, Knorr? It’s The International Space Station Calling

October 9th, 2012 by Maria-Jose Viñas

By Eric Lindstrom

Friday, 5 October 2012 – We got a call today from the Commander of the International Space Station (ISS), Sunita “Suni” Williams. Suni, who was calling while the ISS was passing over Eastern Russia, wanted to congratulate us on our SPURS expedition.

Sunita Williams, Commader of International Space Station.

Eric Lindstrom, Adam Seamans, and Ray Schmitt, during call with the ISS.

We had 30 minutes of wide-ranging conversation about life at sea and life in space. We talked about the beautiful sunrises and sunsets viewed from both Knorr and the space station. Suni has the added bonus of seeing the aurora from ISS and the green flash of the sun lasting for an extended period.

We talked about the naming of the new WHOI research vessel after astronaut Neil Armstrong, which will provide yet another link between space and oceanography for years to come. We talked about superstitions on ships and the ISS — no whistling on the ship seems to be a Navy tradition common to both our vessel and the ISS.

The call was a big boost to morale on the Knorr as we suffered through a day of windy and bumpy conditions inflicted by Tropical Storm Oscar. On the good side, we are finished with our primary science tasks and we are riding the wind and waves toward the end of mission in the Azores.

The talk with ISS also is symbolic of the many and growing links between the exploration of the solar system (outer space) and the exploration of the ocean (inner space). As the Physical Oceanography Program Manager at NASA Headquarters, I see the links every day. However, I suspect that, for starters, many of you were unaware that NASA had anything to do with exploring the ocean. So let me fill you in!

I think there are at least three categories of relationships between inner and outer space to tell you about – first is astronaut skills and training, second is the naming and use of spacecraft and ships as exploration and observation platforms, and third are the intersections in science, remote sensing, and robotics for exploration.

Astronaut Training and Skills

Astronauts must train to live and work in a weightless environment. That is quite difficult to find on Earth, but working under water provides a useful analogue because diving can simulate both weightlessness and working in pressure suits.

The Neutral Buoyancy Laboratory at Johnson Space Center is an enormous pool of water for training astronauts. The NBL contains full-sized mock-ups of the International Space Station modules and payloads.

The NOAA Aquarius Reef Base is an underwater habitat used by NASA on a regular basis for astronaut training.

Few humans posses the construction skills needed to build and maintain the International Space Station. To find qualified astronauts for that work, NASA looked to the deep-sea diving community for “the right stuff”.

Naming of Ships and Spacecraft

Naming spacecraft after ships of exploration (for example, the Discovery and Challenger) has been popular and it seems appropriate that oceanographic ships are named after explorers. The replacement for R/V Knorr was just announced and it will be named the R/V Neil Armstrong after the first astronaut to walk on the moon. Maybe this symbolizes a renewed decades-long commitment by NASA to seagoing exploration and discovery?

The space shuttle ushered in a new regular opportunity for astronauts to view and photograph the Earth and ocean. Similarly, oceanographers on ships can observe the same phenomena at sea level to provide in-depth views.

Science, Remote Sensing, and Robotics

NASA supports the development and use of technologies to explore remote hostile environments across the solar system. Many of these technologies are road tested on Earth in analogue environments, such as deserts, the Arctic, Antarctica, and deep ocean hydrothermal vents. Since we believe there are other oceans in the solar system to explore, like Europa, there is a growing interest in using the Earth’s ocean as a proving ground for remote sensing and robotic technology. This has been going on for more than 30 years.

In 2011, NASA launched the Aquarius mission to study variations in the surface salinity to the ocean. Aquarius senses the ocean at L-band (microwave emissions) in a frequency protected for radio astronomy. There are numerous galactic sources for L-band radiation and these have been well mapped by NASA astronomers. The fact that the radio astronomer’s map is reflected off the sea surface, makes for and interesting connection between the inner and outer space.

For years, oceanographers have been training astronauts for visual observation of the ocean and photography from space, and in turn the astronauts have produced many images of interesting oceanographic phenomena  from above.

In the coming years, ISS will be home to a NASA Physical Oceanography/JPL-constructed instrument to measure winds over the ocean. It’s a follow-on from the QuikSCAT project of 1999 that is still flying today. The new project is known as Rapid Scat and is under development for the Columbus module on ISS.

So that’s a quick tour of some of the inner and outer space connections. The longer this oceanographer works at NASA, the more he discovers. It’s a quite fruitful relationship. It was great to have a Navy Captain in space talking to oceanographers at sea today. Suni William, best of luck on the rest of your mission on International Space Station – and no whistling!

Sunset on the Sargasso Sea.