Why we care about the Southern Ocean

Towering ice bergs. One of my favorite photos from this cruise, courtesy of Hannah Dawson.

A couple posts ago, I discussed the Kerguelen (Ker-gway-len) Plateau and why it was important to the Southern Ocean. In this post, I would like to step back a bit further and talk about why we care about the Southern Ocean in the first place. Here, I will try to describe the uniqueness of the Southern Ocean and the important role it plays in the global climate system. My hope is to provide readers, especially those who don’t have a background in oceanography, a bit more context for the work that we do.

When oceanographers refer to the Southern Ocean, they usually mean the oceanic region south of about 45 degrees south. One key feature of this ocean is that it spans all longitudes. As you can observe from the schematic below, there are no land boundaries in the latitudinal bands of the Drake Passage (the opening between South America and Antarctica). This allows for the existence of the Antarctic Circumpolar Current (ACC), a strong eastward current system that circles around Antartica.

The schematic above shows the major currents of the Southern Ocean. The main current system is the eastward flowing Antarctic Circumpolar Current or the ACC. 'C.', 'G.' and 'F.' are abbreviations for current, front, and gyre, respectively. Source: Rintoul, S. R.,  C. Hughes and D. Olbers, The Antarctic Circumpolar System, 2001.

In terms of volume transport, the ACC is the most powerful ocean current in the world. Even though its average speed is relatively small (about 0.2 meters per second), its depth varies between 2000-4000m and is over 3000 km at its widest point. 

One of my undergraduate professors loved to describe the ACC as an "egg-beater". In that sense, the Southern Ocean is a giant mixing bowl and the ACC acts as a mixer that blends water masses¹ from all the other oceans. The ACC mixes water masses from the Pacific, Indian and Atlantic ocean basins and creates new water masses, which it then exports back into the global ocean. So that's the first major feature of the Southern Ocean. It's the ocean that links all the other major oceans and it is the main cog in the global ocean circulation system.

The ACC is driven by strong westerly (eastward flowing) winds. These westerlies mainly lie in the 40-60S latitude band and are some of the strongest surface winds in the world. Early navigators of the Southern Ocean referred to these winds as the Roaring Forties and Furious Fifties. Those winds lived up to their names during the first 10 days of our cruise.

Even on the calmest days, the winds of the Southern Ocean are still quite gusty.

Due to the Coriolis effect, these eastward flowing winds push the surface waters of the Southern Ocean northwards - away from Antarctica. This effect is due to the Earth's rotation about its axis. The result is a counterintuitive phenomenon where (large-scale) surface currents² in the ocean move 90 degrees relative to the direction of the surface winds. In the northern hemisphere, the Coriolis force deflects ocean currents 90 degrees to the right; in the southern hemisphere, the same force deflects ocean currents 90 degrees to the left. 

This large-scale motion of surface water away from Antartica is a really big deal. In fact, it is perhaps the most important feature of the Southern Ocean. Since winds are moving surface water out of the Southern Ocean, there needs to be a compensating flow to bring water to the surface. This compensating flow comes from the great depths of the global ocean. Thus, the Southern Ocean features large-scale upwelling of deep water to the surface.

A schematic of deep water upwelling and formation in the Southern Ocean. Source: http://dimes.ucsd.edu/en/

The surface layers of the open ocean are generally nutrient deplete. Most of the nutrients needed to sustain marine life are stored in the dark depths of ocean, beyond the reach of most organisms. However, due to the strong and persistent deep water upwelling, the surface layers of the Southern Ocean are flush with nutrients, which form the basis of a flourishing and vibrant marine ecosystem. 

Giant petrel in flight. One of the many sea birds that call the Southern Ocean home. 

Another Giant Petrel. This one flew within 10 feet of the bridge.

A wandering albatross in flight.

The Southern Ocean is arguably the breadbasket of the global ocean. The waters in this region are stocked with phytoplankton and krill, which form the base of the marine food pyramid. The Antarctic Krill, in particular, is one of the most abundant animal species on the planet in terms of biomass. Because of this surplus of food,  migratory animals such as blue whales, orca and albatrosses travel thousands of kilometers to feed in the Southern Ocean. Additionally, the nutrients that don’t get consumed in the Southern Ocean are exported by ocean currents to the other parts of the ocean. Much of the nutrients that get consumed in the rest of the ocean are first upwelled in the Southern Ocean.

A wandering albatross taking a break from flying. Photo courtesy of Hannah Dawson.

A small penguin decided to investigate our ship. This was the highlight our day.

In addition to supporting deep water upwelling, the Southern Ocean is also key location for deep water formation. Surface conditions around Antarctica are below freezing for most year, which leads to the formation of sea ice. When sea ice forms, it pulls freshwater from the surface ocean, leaving behind a salty solution in a process called brine rejection. 

The rejected brine solution from ice formation is relatively salty and cold, and is more dense than the surrounding surface water. Under the influence of gravity, this water sinks to the interior of the ocean. The densest of these deep waters is Antarctic Bottom Water (AABW). The AABW flows away from Antarctica to occupy the deepest layers of the Pacific, Atlantic and Indian oceans.

Putting everything together, we can start to appreciate the Southern Ocean’s central role in not only the global ocean circulation but also the global climate system. When AABW is formed, it brings with it enormous quantities of heat and carbon to the deep ocean for longterm (not permanent) storage. In this sense, the Southern Ocean acts as a huge buffer for the climate system. Because of this, we are being spared from the most detrimental consequences of global warming in the short term. On the flip side, since deep water also upwells in the Southern Ocean, it is also release valve for heat and carbon stored in the deep ocean. The net effect of these processes remains poorly understood.

Even though the Southern Ocean is a central cog in the earth’s climate system, it is still a largely unexplored frontier. Due to insufficient data, many fundamental scientific questions remain unanswered. Much of this is due to the region's remoteness and harsh climate. Research ships like ours can only access the Southern Ocean in austral summer when sea ice is at its minimum. Even then, we can only sample relatively small portion of the ocean for a relatively short of period of time.

Let me give you a hand. Alison and Natalie tag teaming to cock the bottles on our rosette.

Dave prepping our rosette for deployment. Even though we collect a lot of high quality data on this cruise, we can only afford to do so for a few weeks at a time. To fully understand the Southern Ocean, we need to continuously monitor it throughout the year.

This urgent lack of data is what helped to spur the creation of the SOCCOM program. A major goal of SOCCOM is to expand our current observational network of the Southern Ocean. With our next generation Argo floats, we will be able to remotely track the physical and biogeochemical processes that occur in the ice-covered parts of the Southern Ocean throughout the year. This is something we have not been able to do until now.  

Navis SOCCOM floats in the UW float lab being prepped for deployment.

So, this is my summary of why the Southern Ocean is important. It is by no means an exhaustive review of Southern Ocean oceanography, but I believe I covered many of the major points. In a future post, I hope to go discuss my own research focus in more detail.

Until next time,

Earle

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1 A water mass is how oceanographers refer to ocean water that originates from a particular region with certain identifiable properties. For example, North Atlantic Deep Water is a type of water mass that originates from the North Atlantic and is known to be relatively warm and salty. ^↩

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2 By large-scale, I mean distances greater than about 50 km or more. The Coriolis effect (due to the Earth’s rotation) is generally only apparent over those large distances. It would be extremely difficult to observe this phenomenon in small pond (or a toilet bowl). ^↩

Floating into the night

As of today, Tator Tot and Pi have been deployed! Both were released in the turbulent wake of the Kerguelen Plateau and the UW float group have confirmed that both floats have self-activated. The float engineers are currently monitoring their progress. Hopefully, we will get to see their first full profiles soon.

It just so happened that both deployments happened in the dead of night. This is really unlucky seeing that we have about 19 hours of daylight here. Joseph Gum, one of techs onboard, was kind enough to provide these photos. Enjoy.

Cleaning the optical sensors one last time before deployment.

Susan giving me a hand with the float. It's actually light enough for one person to carry.

Float on deck. Time to get our release lines ready. It's important to measure out the just the right length of rope to get the float into the water. Too much rope increases the probability of snags. We learned that the hard way.

Rope measured and tied off. Check. Permission from bridge. Check. Time to hoist Tator Tot into the wild.

Splash down. Last step is to slip the rope and let Tator Tot roam free.

Next stop: The Kerguelen Plateau

After reaching our southern most station 2 days ago, we turned around and began our slow march north, along the I08S line. So far, we have completed 9 stations. In 4 weeks, we hope to complete 100. It's a tight schedule, but Alison is making sure we stay on track.

Since we started on the continental slope of Antarctica, the first several stations were shallow and closely spaced together. This meant the CTD watch standers had very little no downtime while on shift. At the end of my 12 hour watch, I was completely beat and I think everyone else felt the same way. On the plus side, those of us who were on night shift did get to witness a breathtaking sunrise. It was almost as if mother nature sensed our despair and felt the need to lift our spirits.

Sunrise after the first day of sampling. Even though we were on a pressing schedule, Alison made sure everyone on duty had a chance to soak in this view.

In other news,  I will deploy my first Argo float in less than 12 hours! That's right. The floats I described a few weeks ago are about to see the ocean for the first time. This will happen at station 11, when we are near the Kerguelen Plateau.

So what's so special about the Kerguelen Plateau (pronounced Ker-gway-len)? The plateau is a submerged microcontinent, about three times the size of Japan, located about 3000km southwest of Australia. To get sense of its importance, imagine a large boulder obstructing a fast moving river. The boulder will deviate the flow around it and generate turbulence in its wake. This happens even if the boulder is completely underwater. So not only does the boulder disrupt the river's flow in its immediate vicinity, it also creates disturbances that ripple far down stream. The Kerguelen Plateau has essentially the same effect on ocean circulation but on a much large scale.

The payload. Tator Tot, Earle's Hurl, Pi, Eep, Z-Pod, X-Pod and Kaia are stored in the 5 crates to the right.

In related news, I also learned that there are special names for the floats that I will deploy on this cruise. They are Tator Tot, Pi, Eep, Z-Pod, X-Pod and Kaia. These names were chosen by the fifth graders in Jamie Monkonnen's science class at Lakeside School. Tator Tot will be the first to venture out into the deep and mysterious water of the Southern Ocean. Two days later, Pi will join Tator Tot and combined they will help us understand how the ocean behaves in the wake of the Kerguelen Plateau!

Ok, I need to get some sleep before the deployment. Till next time!

-Earle


Edit: There were originally 7 floats but one (Earle's Hurl) had mechanical issues and was sent back to Seattle :(.

Let the sampling begin!

After 11 days of transiting through cold and treacherous waters, we finally made it to our first station! We ended up steaming a bit west of our original line to avoid sea ice (the Revelle is not an ice-breaker), but that gave us the chance to go a bit further south and dip below the Antarctic Circle (~66.33 S). Now we can officially say we have visited the Antarctic! 

Never missing a chance to commemorate an occasion, the crew decided to pose in front of one the many icebergs we saw this morning.

There wasn’t much time to lollygag though. We have a long month of sampling ahead of us and time is of the essence. Within minutes of our arrival, the science team and crew lowered the CTD into the water to start our first cast.

Josh, our res tech, getting reading to guide the rosette into the water.

It just so happened that we arrived at station 1 at 11:45am - 15 minutes before the end of my shift. After quickly prepping the rosette for deployment, Natalie and I passed off after our responsibilities to Seth and Hannah, who then took over the CTD watch. After staying up all night, I really should have gone to bed, but how could I when there is so much exciting things happening around me? Instead, I spent the next hour or so recording our first day of sampling. My shift is in 8 hours, so I will just dump these photos here for the time being.

That's all for now!

-EW

Hannah and Seth on the first CTD watch. Seth probably computing the next wire-out.

CTD back on deck. Let the sampling begin!

Viviane (our co-chief scientist) gets to be sample cop on station 1.

Look! An iceberg! It was well below freezing with windchill. I will keep my layers on, thank you.

Phil and I had a "shoot off".

Aurora Australis!

Tonight I saw the Southern Lights for the first time! Without a doubt this is one of the coolest things I have ever witnessed. As soon as the bridge caught first glimpse of the spectacle, they relayed the news around the ship. Even though it was 2:30am on the ship, the bridge was filled with awe-struck star gazers within minutes. The entire scene was surreal. The green tinged sky, choppy seas and sub-Antarctic wind made me feel like I was on a different planet.














It was actually quite difficult to photograph the aurora on a moving ship. The dim lights combined with the shaky platform, pushed the limits of my camera. The photos don't do the scene full justice, but I hope you can still appreciate its beauty.

Still Steaming

Day 9 (or is it 10? I’ve lost count.)

It’s 3:00am* on the Revelle. The ship is mostly quiet save for a handful of scientists taking underway samples through the night. I have no duties tonight though. We are still 2 days from our first station and the first Argo float does not go overboard until another week or so. The only reason I am awake this “late” is to prep my body for my upcoming night shift assignment. Given the exorbitant cost of operating a research vessel (roughly $40,000 USD per day from what I gather), most science groups split their personnel into night and day shifts. I am on the midnight to noon shift for the CTD watch. My other night shifters, Natalie and David, are also in the process of reprogramming their body clocks. They are trying to keep themselves awake by watching movies in the lounge. I have been reading The Martian for the same effect.

Strapping in for a rough day at work. This mug belongs to Mary (our computer tech).

The previous two nights were quite eventful. We got hit by a powerful storm that sent 30 foot waves crashing onto our deck. The strong winds combined with the powerful swells tossed our 273 foot vessel from side to side as if it was a plastic cork going down a rapid. Nothing is easy when the ground beneath you is swinging back and forth like a pendulum. The hardest part of my day was putting on my pants without falling on my face. 

Rough times in the Southern Ocean. Everyone was basically trapped inside for about 3 days. This video was taken behind the safety of a water-tight door.

My least favorite aspect of the storm was the noise. Fun fact: when waves crash against a ship's hull, they sound like battering rams. The banging of the waves started the moment we left port, but the storm amplified the ricochets many times over. Needless to say, I slept very poorly over those few days. As I laid in bed, I just imagined myself being trapped in a giant snare drum, hurtling down a bumpy hill.

The calm after the storm. The air was so clean and the water was so clear.

After two hellish nights, the storm abated and the skies became clear again. I managed to recoup most of my sleep and was grateful for the much quieter (but still loud) sound scape.  The swells are still large, so the deck remains off-limits. However, I did get a brief opportunity to breathe some fresh air today since I volunteered to launch an XBT (a temperature probe) off the stern of the ship.

The air is much colder now. Afternoon temperatures are just above freezing even though it is currently in the middle of summer. We are approaching 60S on a new course that has been re-configured to avoid unexpected sea-ice. In a few hours, we should start seeing small chunks of floating ice.

One of the two of grey-headed albatrosses I saw yesterday. These majestic birds are native to the Southern Ocean and spend much of their lives over the open ocean. They have been following our ship for the past couple days.

I was hoping to the Aurora Australis (aka the southern lights) tonight but the skies are too cloudy. A few people got a peak of it last night, but I was in deep slumber at the time. Fortunately, I am on the night shift, so I will have many chances to witness the amazing spectacle myself. That alone would make-up for the roll-coasters nights I had to suffer through.

That is it for now. I am itching to finish the rest of my book - it’s so good. Hopefully, I will have some great photos of icebergs in my next post!

Catch you later,

Earle

*I later realized it was actually 2 am because we entered into a new time zone a few hours earlier.

From the Revelle, with Love

Day 7: Somewhere in the southern Indian Ocean

After the initial flurry of activities at the onset of our cruise, life on the Revelle has slowed to a quiet lull. Part of that has to do with the energy sapping, cold virus that has been making its rounds through the science crew. My immune system finally gave out yesterday and rumor has it our chief scientist is the latest victim. The bright side is that we don’t arrive at our first station for another four days, so everyone should have enough time to recover.

Still, despite all the sniveling noses and watery eyes, everyone is in good spirits. The extended downtime has given everyone onboard the opportunity to bond and become more acquainted. For me, it has been a very enlightening experience hearing snippets from everyone’s life story. Even though we are all oceanographers in some sense, each of us took a unique and interesting path to arrive on this cruise. Even among our small group of CTD-watch standers, we have people hailing from all over the world. The places that we call home range from the pastoral plains of Kansas to the great expanse of Western Australia. Inadvertently, this cruise has facilitated a delightful cultural exchange. For example, earlier this week, the Aussies in our cohort introduced us to vegemite and were entertained by our bewildering reactions (my verdict on vegemite is still pending). A few days later, when the cooks served warm bagels for breakfast, we had the pleasure of introducing them to the wonderful world of fresh bagels and cream cheese.

Alison teaching us how to play Cribbage.

Even with all the quirky differences between our cultures, what struck me the most are all the similarities we share. No matter the subject matter, we always seem to find a common ground. Whenever someone shares an anecdote, at least one person always has a parallel experience.

One of the ways we socialize is by playing card games in the library. This has become my go to way of passing time whenever I am too tired to work, but too buzzed to sleep. The library, which annexes the mess hall (cafeteria), is the social hub of the ship.  I learned about a half dozen card new games this week, including Cribbage which has become a crowd favorite since Alison taught a handful of us.

The dashing Roger Relove...

It is Valentine's Day today and everyone woke up to a Valentine's Day card (thanks Natalie and David I mean Roger Relove). The cooks also offered us decadent chocolate treats to go with our lunches. It seems like the Revelle’s crew never miss an opportunity to celebrate. I learned that the cooks will bake a giant cake for anyone who has a birthday while at sea. Yesterday, Jim Happell was that lucky guy and everyone had their fill of delicious lemon cake. Even from my short stay onboard, I have come to appreciate that this floating research facility is a second home for a lot of people. These small gestures, as mundane as they might seem, really do go a long way in creating a home away from home.

We are currently getting thrashed by monster swells from a passing storm, but our vessel is built to handle much worse. Instead of showing you scary images of waves breaching our deck, I will leave you with the calming sunset we had a few nights ago.

Sunset from the Revelle's deck. Antartica lies in the horizon.

-EW

Shout out to Lakeside School!

Lakeside is an independent school in Seattle for grades 5-12. As part of the outreach effort for the SOCCOM program, I will be working with Jamie Monkkonen and her middle school science class. Many thanks to Jamie for making this possible!

CTD watch-standing 101

February 11, 2016: Day 4

We have now completed almost four full days at sea. Wo Hoo! For some reason, it feels a lot longer than that though. I suppose it makes sense given how much has transpired this week. Since my last update, we completed a test station about 250km southwest of Australia. This gave all the scientists a chance to walk through all their procedures and iron out any glitches before arriving at the I08S line.

A rosette being lowered over board. This is from an earlier cruise I did.

A station is basically wherever we stop to collect data. When we arrive at a station, we lower an instrument called a rosette into the water. The rosette is the workhorse of modern day observational oceanography. It consists of metal cylinders (called Niskin or Nansen bottles), arranged in a circle, with spring loaded caps on either end. When the rosette goes into the water, the caps are cocked open, allowing water to flow freely through the cylinders. The caps on each bottle can be released remotely from the ship, and they are fired in sequence and at specified depths. The rosette on our ship has 36 bottles, which means we can use it to collect water samples from 36 different depths.

In normal operations, we lower the rosette to just above the seafloor and trigger each bottle as we bring the instrument back to the surface. The maximum depth along our cruise track is about 4000m. Lowering the rosette to that depth and bringing back up to the surface takes about 4-6 hours.

In addition to collecting water samples, the rosette serves as a platform on which we can mount many different instruments. The most important instrument of them all is the CTD. CTD stands for conductivity, temperature and depth, which are the bread and butter variables of oceanography. Conductivity is a proxy for salinity. So a CTD tells us how salty and warm the ocean is at different depths at a particular location.

A sketch of a rosette suspended in water. The winch operator only knows the wire out. The CTD watch-standers have to guide him to the target depths.

In previous posts,  I talked about deploying Argo floats for SOCCOM. However, my main responsibility is to be a CTD watch-stander. There are five CTD watch-standers on this cruise - all of us are graduate students. As CTD watch-standers, we assist with all stages of the rosette’s deployment and recovery. One of our main functions is to direct the winch operator as he lowers/raises the rosette through the water column. In a simple world, we would just tell the winch operator to bring the rosette to certain depth then fire a Niskin bottle to collect a sample. However, in practice, the wire out does not equal the depth of the rosette/CTD as horizontal currents in the water column will tend to push the rosette away from the ship. This is where we come in.

CTD-watch training at the test station. Each student took turn communicating with the winch operator.

The CTD watch-standers sit in a computer room and have access to all the live readouts coming from the rosette’s instruments. We know the true depth of the rosette as well as the wire out. By doing simple math, we can tell the winch operator how much cable to let in to bring the rosette to a certain depth. When the rosette reaches its target depth, we fire a bottle to collect a simple. The most critical part of this task is the bottom approach. On most casts, we would like to get a sample 10m above the seafloor. If we overshoot and hit the bottom, we can seriously damage our instruments. This of course would be very, very bad. 

In addition to guiding the winch operator, we monitor all the sensors on the rosette and log any interesting or unusual signals. There is a lot to keep track of, which is why a CTD watch is usually a two person job.

Dana collecting a water sample at our test station. 

Once the rosette returns to the deck, all the scientists quickly flock to the apparatus to collect all the precious data. Everyone takes turn accessing each bottle and the chief scientist on duty ensures everyone goes in a particular order. After all the sampling is done, the bottles are emptied, rinsed and prepped for the next station.

On our cruise, we will occupy about 100 different stations and collect 36 water samples at most of them, so it is critical that everyone works as efficiently as possible. This is especially true for us, CTD watch-standers. If we waste a minute collecting each sample, that amounts to extra 3600 minutes or 2.5 days by the end of the cruise. To put that into perspective, each day we spend at sea costs about $40,000 USD. Therefore, every second counts.

Wind forecast for this upcoming weekend. Just another day in the Southern Ocean.

It will be another five days or so before we arrive at our first station. The actual time of arrival will depend on weather conditions, which is looking pretty gusty at the moment. We just crossed into what is known as the "Roaring Forties", which refers to the strong surface westerlies found in the 40-50S latitude band. Sure enough, a storm system is forecast to cross our course in a few days. After we will through pass that, we will move into the "Furious Fifties" and "Shrieking Sixties". Fun times...

Catch you guys later.

-EW

Off we go!

The gangway has been raised and the ship has left its berth! As of two hours ago, we have spent our first full day at sea. So far, my motion sickness pills seem to be doing their job and I am very grateful for that. Some of my fellow crew mates have not been so lucky. The first few days at sea are usually the worst but after a while your body usually learns how to cope. My sea-legs are not quite there though. Standing still remains a struggle.

Most of the science crew were on deck to watch the ship leave the harbor.  Photo courtesy of Alison Macdonald.

The past 36 hours have been hectic. The entire crew participated in numerous safety demonstrations and evacuation drills. Additionally, all the student volunteers, myself included, began our on-the-job training. This was a lot of information to absorb in one day but we were assured we will get the hang of everything in short time. Before we left, Rick also gave tutorial on how to float deploy Argo floats from the ship. All the students were in attendance and it was a great learning experience for everyone.

Rick educating all the students about the Argo/SOCCOM program. Photo courtesy of Alison Macdonald.

For the next 9 days or so, we will transiting due south to the Antarctic shelf where we will begin collecting ocean samples and deploying Argo floats. Over this transit period, Alison, our chief scientist, will see to it that her entire science will be prepped and ready to go when we arrive at our first station. Tomorrow we will make a brief stop a few hundred miles south of Australia and do a dry run of a station sampling. Basically, everyone will go through all their data collecting procedures as if they were at their target locations. 

The red line roughly outlines our course over the next 9 days. The purple line shows where we will stop to collect data and deploy instruments.

Ok guys, that's it for now. Next time, I will try to talk a little bit more about what we are trying to do on this cruise.

Freo!

I have arrived! My transcontinental journey went by without a hitch and I arrived in Fremantle (aka Freo) at around midday yesterday. It's summer here. The air was a toasty 100 degrees F when I stepped out of the airport and there wasn't a cloud in the sky. The warmth and scenery reminded of southern California. After a 30 minute cab ride, I finally made it to the Revelle.

The R/V Roger Revelle!

The ship was already bustling with activity when I got there. Both the science and tech crew were making final preparations for the journey ahead.  Alison, our chief scientist, greeted me on the deck and introduced me to everyone within sight. I met my fellow student helpers and instantly made new friends. I eventually met up with Rick (see last post) who is only here to ensure that the floats make onto the ship in working order; he flies back to the US in a few days. He informed me that one of the floats had a mechanical failure and will have to shipped back to Seattle. That means we will be deploying a maximum of 6 floats on our cruise.

One of the main streets in Fremantle

Later that evening, we had dinner in town and I got to do a bit of sightseeing. Fremantle is one of the major port cities in western Australia and has a rich history of European settlement. The British influence is obvious but there are visible traces of Italian and Portuguese influences as well. The atmosphere is very laid back. Everyone seems to just want to relax and have a good time.

Street artist in downtown Fremantle

Loading cranes in Victoria Quay. Don't they look like
mechanical dinosaurs?

Tomorrow is our final day in port. We set sail at 16:00 and all hands must be on deck two hours prior. Rick will also host "float school" at 08:00 where he will teach everyone, who cares to learn, the proper procedures for deploying an Argo float.

Till next time,
EW

UW Argo lab

The view through my terminal window is wet and gloomy and the weather seems to be lulling everyone to sleep. Typical day in Seattle. However, today I am immune to the somnolent spell of the city because, in just a short while, I will depart for Fremantle, Australia to begin my cruise through the Southern Ocean!

Before I leave, I would like to recount my last visit to the UW Argo float lab. Last week, I asked Rick Rupan, our lab manager, to give me a tour of the operation he oversees. He was more than eager to participate. He spared no details as he walked me through all the intricate details of float design, testing, assembly and deployment. That experience left me with great appreciation for all the work that this lab does. I will try to summarize.

Our lab is one of a handful groups in the world that assembles and deploys profiling floats for the Argo program. Argo is a global array of profiling platforms that allows us to remotely monitor the state of the ocean. These floats freely drift through the ocean and sample the upper 2000m of the ocean on roughly 10 day intervals. The first Argo float was deployed more than 15 years ago and the current observing network now boasts over 3900 floats worldwide.

The standard Argo floats measure temperature and salinity. However, a small but growing subset of these floats are now being equipped biogeochemical sensors that can measure ocean properties such as oxygen, nitrate, pH and fluorescence. The floats that I will deploy for the SOCCOM project belong to the latter category.

A close up of the sensors on a biogeochemical Argo float.

Our lab assembles and ships both standard Argo floats and their souped-up biogeochemical counterparts. The UW float team mainly deals with a particular model of floats known as APEX floats, which are manufactured by the Teledyne Webb Research company. More recently, they also have started working with the NAVIS model from Sea-bird electronics. All these floats do essentially the same thing but work in slightly different ways.

When the floats arrive at our lab, they are fully assembled and usually work right out of the box. But, these floats are expensive. A fully equipped biogeochemical float, for example, costs roughly $80,000 USD, so Rick needs to ensure that we can get the maximum performance out of each float.

Rick and Christina tinker with the electronics of an Argo float.

To prolong the lifetime of these instruments, Rick and his crew subject them to a rigorous course of quality control testing. They start by stripping the floats down to their bare essentials and perform tests on each component. Every piece of the float, from the pumping mechanism to the control board to the sensors, is scrutinized for defects and deficiencies. Part of this process also includes ballasting, where they submerge the float in a special tank to calibrate its buoyancy and test its ability to remain upright in the water. Rick's group is able to fix most problems in-house but occasionally they have to return particularly defective components to their manufacturer.

Rick showing the internal electronics of a regular Argo float that only has
temperature and salinity sensors (right) and a SOCCOM float that has
a full suite of biogeochemical sensors (left).

The floats that arrive from APEX only have temperature and salinity sensors on board, so the group has to install all additional sensors. For SOCCOM floats, this step involves shipping them to our partners at the MBARI oceanography center in Monterey Bay, California. The MBARI group installs sensors for pH and nitrate then ships the modified floats back to UW. As you can tell from the picture above, these extra sensors add a lot of bulk to the float. For this reason, SOCCOM floats are slightly larger than regular Argo floats.

Typical turnover time for float testing and rebuilding is usually about 2 weeks. But, after Rick's crew work their magic, each new float is sent out with an expected lifetime of 4-5 5-7 years.

Map showing the location of all current Argo profiles, as of
February 4, 2016

In some ways, the UW lab is like a factory. Even though the group is small, the complicated logistics of the Argo program requires the lab to operate like clockwork. Every float that gets deployed will eventually die, so we have to continually build new floats to maintain the existing coverage. In 2015, the UW float assembled and shipped roughly 120 floats, which is a substantial fraction of the 800 that were built globally.

In this blog post, I only mentioned 2 people, Rick and Christina. However, many more people are involved in the pre- and post-Argo float production process. I would be remiss to not mention Professor Steve Riser (principal investigator and also my advisor),  Dana Swift (senior research engineer and one of the technical masterminds behind the Argo project) and Annie Wong (senior research scientist and data quality control expert). There other important people that I don't have time to acknowledge but you can see full group here. It is through their collective hard work and dedication that the Argo program is as successful as it is today.

That's all for now! My next update will be from Australia. Rick has already flown ahead to retrieve the SOCCOM floats from shipment and load them onto the research vessel.

 -EW