Monthly Archives: January 2015

Falkor: We’ve Got Data!

The moment that all field scientists crave has arrived – preliminary data!  Team T-Beam ran two successful profiles and are hot on the trail of identifying the area of highest energy of the internal tide.  Here’s an update of their progress so far.  During a preliminary 30 hour period, the ship steamed back and forth across a 200km transect thought to be the most likely location of the T-Beam (Transect C1 – C2).  The midpoint of this transect marked the location of one of the moorings deployed by the Revelle. During this trek we traversed the transect six times and the shipboard ADCP collected water velocity data down to 800 meters depth.  As we’ve discussed before, the ADCP measures current velocity in two orthogonal directions, North-South (the V-velocities) and East-West (the U-velocities).  Taking these two directional velocities together gives a picture of the overall trajectory of the current.  Remember that the internal tide is driven by the semi-diurnal tidal cycle and the tides move in a back and forth direction (like when the tide comes in and then goes back out on a beach). The semi-diurnal tide in the Tasman Sea should move bi-directionally along a NW – SE line.
Contra plot

This contour plot shows the amplitude of the current velocity with depth along a 200km transect (100km on either side of mooring A1 at 0).  The blue astrix indicates the location north (negative numbers) of the mooring buoy that shows unusually high velocities that are likely associated with the internal tide. SOI/Amy Waterhouse, Sam Kelly and Luc Rainville

A sign of the sine wave

In addition, the velocities of the semi-diurnal tide over time will fit on a sine curve.  What this shows is the velocity speeds up and slows down at different times in the cycle (for example, when the tide is all the way in, the current speed approaches zero).  The velocity also changes direction (positive and negative) depending on whether the tide is coming or going.  Here’s where the preliminary data provide some promising results.  When the science team plotted all of the ADCP velocity data onto a graph, the velocities over time fit onto a sine curve with the correct period – a good indication that the data are representing the expected tidal cycle.  Also exciting is that the relationship between the U velocities (N-S) and the V velocities (E-W) indicates that the current is moving in the same directional angle as the T-Beam.  So they are pretty sure that they’ve found the internal tide beam!!  Previously the location of the internal tide beam was only predicted by a (very sophisticated) computer model.  This is what scientists call ground-truthing a model.

Sine wave

Plot showing the velocity sine wave of a tidal cycle. http://en.wikisource.org/wiki/The_American_Practical_Navigator/Chapter_9
velocity graph

Another graph showing a large increase in velocity in both U and V directions around 30-60 km north of the mooring. Drops and spikes at the very ends of the graph are artifacts of the transect.  SOI/Amy Waterhouse, Sam Kelly and Luc Rainville

Planning the next step

Another interesting development is that there is an area along the 200km transect that shows much higher velocities than the surrounding areas. This can be seen in a graphic called a contour plot, which uses color to visualize velocity and direction through the water column.  In this contour plot, there is an area (*) where the velocity is very high (dark red/black). Could it represent the center of the T-Beam?  We don’t know for sure just yet, but not surprisingly, this is the location that the science team decided to conduct the first full LADCP/CTD profile (F2).

Shipboard ADCP transect (line connecting C1 to C2) and the locations of LADCP/CTD profiles at F2 and F3. Google Earth/Amy Waterhouse

The second profile was located further north along the transect (F3). Each of these profiles was conducted over 30 hrs between the surface and 1700m depth, with a full cast (up and down) occurring every 2 hours.  Those data now await further analysis, as the scientists decide their next move.  At the moment, we are back in port for a few hours picking up some new equipment and preparing for another round of profiles.

Spencer Kawamoto and Hayley Dosser take advantage of port time switch out the batteries in the LADCPs for the next round of profiles. SOI/Judy Lemus

– Judy Lemus, Falkor

The Tasman Tidal Dissipation Experiment//Supported by the National Science Foundation

Revelle: How did we get here?

Credit: Julia Calderone

John Mickett and Eric Boget discuss a double-anchor mooring drop. Credit: Julia Calderone

Studying the ocean is similar, in a way, to studying the farthest reaches of outer space. Just as we don’t have a full grasp on the physical boundaries that separate deep space from whatever else may be beyond, we don’t, as of yet, have a complete topographical map of the bottom of the ocean. Since light can only penetrate the first layer of the ocean’s surface, many of the physical and biological processes churning about the deepest depths are a mystery.

Oceanographers, as a result, don’t attempt to document each and every swirl, wave or eddy in the ocean. Instead, they practice inquiry-based science. They think about interesting problems in general, and then try to answer them by studying specific chunks or processes in this massive body of water.

An interesting problem for the Tasman Tidal Dissipation Experiment (TTIDE) is climate change. And the project’s goal is to understand how the ocean’s internal dynamics—specifically its hidden yet powerful and enormous tides and waves—interact with the atmosphere to grab carbon dioxide and heat from it to influence our climate.

Selecting a site to study such processes in the ocean is an enormous task. It’s cliché to say, but there really is an “ocean of possibilities.” Oceanographers rely mostly on simulations and models pieced together from data from satellite images and forces from the sun and moon to pick spots in the ocean that they think will be interesting enough to elucidate certain processes. And then they zero in on those sites to study them and then extrapolate those results to other similar parts of the ocean.

Harper Simmons, an oceanographer at the University of Alaska, Fairbanks and one of the head scientists for TTIDE, developed a global simulation of internal tides to identify optimal regions to study these underwater swells. His model (see video below) shows that the ocean is saturated with propagating waves, as represented by pink and blue beams. The Hawaiian Ridge acts as a major generator of these tides, but this region doesn’t harbor much mixing—a phenomenon TTIDE is interested in where crashing internal waves circulate cold, dense water from the bottom of the ocean to the top and pull the warm, lighter water from the top down to the bottom.

P1040860

The mooring team after a successful evening deployment. Credit: Julia Calderone.

Enter the Tasman Sea. Ideally, the team would measure these huge internal waves throughout their full life cycle—from their birth to their “death” when they break. This is challenging since these massive, 30-story-high waves can travel hundreds of kilometers before breaking. But Simmons’ model shows a unique river of tidal energy flowing between New Zealand and Tasmania, a region that is fairly manageable to navigate. So here we are. The team has picked three spots to scrutinize in the region—the point of wave birth near New Zealand, the point of wave propagation in the middle of the ocean, and the point of wave “death,” or where they break, on the Tasman Slope.

By catching this flow of internal wave energy from start to finish, the team hopes to document the physics for the first time, and better understand how this process may play out in other similar regions of the ocean. Even further, such calculations could add another crucial data point to climate models to make them even better than they are.

So here we are. Breaking down complicated physical processes in the ocean, one bit at a time.

Julia Calderone, The Revelle

The Tasman Tidal Dissipation Experiment//Supported by the National Science Foundation

Falkor: Waves in the sky!

Although we are furiously chasing after internal waves underneath the ocean surface in the Tasman Sea, we got a pleasant surprise the other day on a transit between stations – beautiful atmospheric “internal waves” in the sky above us!

– Amy Waterhouse, Falkor

The Tasman Tidal Dissipation Experiment//Supported by the National Science Foundation

Falkor: Looking into the Plastisphere

Whilst Falkor is rushing about chasing internal waves for next few weeks, this platform is also being modestly utilized to hunt down any microplastics that may cross its path. Back in my home state of Victoria, I have been collaborating with researchers Slobodanka Stojkovic and Mark Osborn from the Royal Melbourne Institute of Technology (RMIT), and citizen scientists to investigate the prevalence of microplastics in our local coastal waters.
Microplastics are typically plastics <5mm that can be breakdown or raw material, often as fibres, beads or thin films, made up of either polyethylene, polypropylene, polystyrene, and  ethylene vinyl acetate (Reisser et al 2012). The journey into the Tasman Sea has provided an opportunity to obtain some “baseline” data on microplastics in general, and more specifically for the RMIT researchers a chance to study the make-up of the regional plastisphere.
Albatross

Microplastics can be a major health risk to seabirds such a this Shy Albatross. SOI/Randall Lee

Invisible Risk
The direct nutritional effects of ingested microplastics on organisms such as seabirds and their chicks has become a familiar story.  Lesser known, but potentially equally as important, is that the surface of microplastics present a new substrate in the ocean, which can be rapidly colonized by a complex community of microorganisms. Microplastics in the environment also act as a sponge, by absorbing numerous persistent organic pollutants and heavy metals, that can be many times greater than ambient concentrations.  As such, ingested microplastics can pose a significant pollutant exposure risk to aquatic organisms, with pollutant concentrations accumulated up the food chain. The RMIT researchers wish to expand the limited knowledge of the complex microbial-ecological interactions that occur on plastic surfaces, that will influence the bioavailability, toxicity and subsequent release of plastic co-pollutants into aquatic fauna.

Biofilm on plastic

Bacterial cells (~1.5 mmlong) attached to polyethylene microplastics in U.K. coastal marine sediments. Harrison et al. BMC Microbiology 2014 14:232   doi:10.1186/s12866-014-0232-4

How much is out there?
Concentrations of microplastics in the oceans wildly vary. A recent study in the North Pacific found they ranged from 8 to 9200 particles /m3 (Deforges et al 2014). In the Tasman Sea scant studies have been done, though at lower latitudes Reisser et al. (2012) found that concentrations vary from 500 to 3500 pieces per km2.

Using Falkor’s autonomous sampling system, water is initially passed through a 5mm strainer, before filtering with a 250 micron mesh to capture microplastic samples. Each sample will represent 10hrs of filtering accounting for ~12000L or 1.2m3 volume. These 10 hr samples will be taken throughout the cruise at key locations associated with the companion biological sampling by Dr. Peter Strutton.

Microplastic filter

Filtering microplastics from the outflow of the Falkor’s autonomous surface sampling system. SOI/Randall Lee

The plastic journey…
Each individual plastic fragment present within the marine environment will have been subject to complex dynamic changes in its biofilm community (microscopic organisms that produce a film on the plastic surface).

During a myriad of divergent routes that transition across and between the terrestrial, freshwater and marine environment, each plastic fragment may develop into a unique environmental microhabitat, shaped by travel through differing physical–chemical environments. Adsorption of organic and inorganic chemicals and by colonization of diverse microorganisms produces a sort of fingerprint of their journey. For the region Falkor is operating in, drifter tracks shown in the figure indicate source areas are predominately associated with the East Australian Current system, though some originate from the Indian Ocean and beyond.

Drifters released (asterisks) and pathways relative to Tasman Sea sampled stations (purple) (Adapted from Reisser et al, 2014).

The microplastics being collected by Falkor will be passed onto Slobodanka and Mark to further their investigations into the local microbial community, and general observations of the plastics collected shared with others studying the regional microplastics community. Hopefully, enough data will eventually be collected to provide information to policy makers and resource managers.

– Randall Lee, Falkor

The Tasman Tidal Dissipation Experiment//Supported by the National Science Foundation

Revelle: The Sphere Half Full

Waves_still

Winds blowing at 45 knots on the Revelle. Credit: Julia Calderone.

If you haven’t gleaned this already, studying hidden processes miles below the ocean’s surface is challenging. Even worse, we’re cruising in an unpredictable region in the Tasman Sea, a spot notoriously dubbed the “Roaring Forties” due to the strong winds ripping from the west through the Southern Hemisphere between 40 and 50 degrees latitude. We’re limited to the tools we can carry on the ship, so we come prepared. If an instrument breaks, we shift, rethink and make do with what we have. And the last few days have been a reminder of this.

 

Sunday we recovered a mooring (to re-deploy elsewhere) that had one of the McLane Moored Profilers on it (shown here in a happy pre-deployment status). It robotically climbs up and down the mooring line at a speedy 33 cm/s, measuring temperature, salinity, and velocity as it goes. When it works, it provides an extremely valuable high-resolution view of the ocean by taking smooth, continuous vertical profiles of temperature versus depth, as opposed to the chunky measurements other sensors take from individual spots on the line.

A McLane profiler before it is attached to the mooring line. Credit: Julia Calderone.

A McLane profiler before it is attached to the mooring line. Credit: Julia Calderone.

But a moored profiler is a finicky beast. For starters, it must be “neutrally buoyant,” meaning that it should be “floating” up and down the line in the middle of the ocean like a hot-air balloon in the sky. To do this, it must be equally as dense as the surrounding water. Imagine a dog-chewed tennis ball floating halfway to the bottom of a swimming pool. If it’s either too heavy or too light, it either sinks or floats. Similarly, if the profiler is too heavy, its motor must work extra hard to crawl up and down the line. Therefore we carefully adjust its weight by compensating the heavy stuff inside of it—like the instruments measuring things—with glass balls filled with air to make it light (glass is heavy but air is very light compared to water). The net effect is the fabled Goldilocks juuuuuust right.

When Matthew Alford pulled the data from the recovered profiler on Sunday, he looked at the diagnostics on his computer and then frowned. The poor little motor had been working very hard and the instrument had not been crawling well (“I think I can, I think I can…”). We initially fretted that it had been ballasted poorly, meaning that our formula for adding up the weight was wrong. If this were the case, the formula could’ve been wrong for the rest of the moorings as well. But upon closer inspection, we realized that the profiler was actually heavy (very heavy!) because its internal glass ball had cracked and was not filled with air, but filled with seawater. Doh!

The glass sphere that sits inside the McLane Profiler to help it float in the middle of the ocean is cracked and full of seawater. Credit: Julia Calderone.

The glass sphere that sits inside the McLane Profiler to help it float in the middle of the ocean is cracked and full of seawater. Credit: Julia Calderone.

Manufacturing a glass sphere to withstand the intense pressure of the deep ocean with zero imperfections is a huge engineering feat (it has to endure 10,000 psi, or five tons of weight per square inch).The engineering is usually perfect, but sometimes deficiencies bleed through. Luckily this sphere only cracked and flooded itself. Sometimes a crack can cause the ball to literally explode, taking out everything else in its path. We walked away from this one feeling like we had gotten off pretty light.

 

 

Paul Chua, Matthew Alford and Gunnar Voet staying up late to re-design a last-minute mooring from components we have on hand. Credit: Jennifer MacKinnon.

Paul Chua, Matthew Alford and Gunnar Voet staying up late to re-design a last-minute mooring from components we have on hand. Credit: Jennifer MacKinnon.

Today we take the “sphere is half full” perspective. We were very lucky to have pulled this particular mooring up and notice the problem, instead of letting it be in the ocean half-working for the next two months. Now we have the opportunity to remove the busted profiler from the mooring, re-design a new mooring and throw it back into the ocean. If we were on land, we would spend many weeks carefully designing each mooring, weighing all the components and considering the stress and pressure they each would be subjected to. But sometimes the ocean throws a curve ball and the team must re-design a brand new mooring with only a few hours to spare. Check inventory! Laptops out! Time for more coffee!

—Julia Calderone and Jennifer MacKinnon, The Revelle

The Tasman Tidal Dissipation Experiment//Supported by the National Science Foundation

Falkor: Taking the Ocean’s Temperature

If you’ve been paying any attention at all to the news in the last, say, two decades, you will know that the temperature of the ocean is increasing. Many national and international agencies and non-profit organizations have devoted funding to study these phenomena and they all point to the same answer – Earth’s ocean is getting warmer. Understanding how the ocean absorbs and distributes excess heat trapped in the atmosphere is critically important to understanding how this warming will affect climate and overall weather patterns on Earth.
But temperature measurements of the ocean can also tell us so much more. For example, the NSF-funded projects T-Tide and T-Beam are using ocean temperature to better understand regional scale movements of different water masses in the ocean. As described in previous blogs, water temperature can indicate the location of the passing internal tide as it lifts deep colder water up closer to the surface. Temperature also helps scientists track eddies that may interact with the internal tide. It is also an indicator of larger ocean currents and gyres. So to tease out the internal tide “signal” within this region of the Tasman Sea, the science team is collecting LOTS of temperature data. Here’s a description of the various tools these teams are using to study temperature throughout the water column.
Launching an XBT

Researcher Randall Lee prepares to launch an XBT off the stern of Falkor.  Note the gun’s cable connection to the ship.  SOI/Judy Lemus

Big Rosie
The CTD (Conductivity, Temperature and Depth) instrument on the large rosette, whom I’ve nicknamed “Big Rosie” (just now) measures water temperature at a frequency of 16 KHz, which is 16 times per second. Since Big Rosie moves up and down in the water column at around 60m/minute (1m/sec), this would yield about 16 temperature measurements per meter. This seems like a lot, but in order to provide an accurate picture, the computer programs that visualize the data need to average many measurements for each point on a graph. Since the internal tide generates smaller internal waves of higher frequency, an instrument that samples even more frequently, if available, would give us an even better understanding of the wave profile.

CTD on big rosette

Big Rosie – the CTD instrument mounted on the large rosette.  The orange boxes are the batteries for the ADCPs. SOI/Judy Lemus

Chi-pods
These don’t need a nickname because their real name is already cool.  Chi-pods were developed fairly recently at the Ocean Mixing Group at Oregon State University and can take temperature measurements at 100kHz (100 times per second). They are also mounted on the large CTD rosette, and therefore provide information on the full depth of the water column. This is clearly an advantage for studying smaller scale processes. But because of this, as with Big Rosie, they only sample any given depth of the water column every couple of hours because it takes this long for the rosette to be lowered to the bottom (to 4500m deep) and come up again. Another thing about these little instruments is that their sensors are, well, sensitive, and so can be damaged by anything bumping or brushing up against them. Fortunately, there are many replacements on board, just in case.

Lil’ C(TD)
As mentioned previously, the team is also using a smaller CTD unit, which I’ve just dubbed, “Lil’ C(TD)”.  This instrument is mounted in its own cage and is being deployed every 1-2 hours to just 180m depth. Due to its weight, and the roughness of the seas here, the large CTD is being used to profile the water column below 200m depth. Lil’ C(TD) is giving the team critical information about the water profile at the surface, where much of the mixing and biological activity occurs.  It also now has a pair of Chi-pods as well for high frequency measurements.

Lil'C deployment

Lil’ C(TD) being deployed off the starboard side. SOI/Judy Lemus

Lil’ C with two Chi-pods attached.

XBT
A very simple instrument with a great ‘secret agent’ sounding name. The acronym stands for Expendable Bathythermograph. These have been used for decades to help oceanographers measure temperatures in very deep waters all over the world without the aide of very specialized equipment. They consist of a lead weight, temperature probe (thermistor is the correct term), and spool of copper thread, deployed from a gun with an electronic sensor directly attached to the ship’s data port. The copper thread stays connected to the gun, which sends the information back to the ship, where it is displayed in the control room. The weight falls at a known rate and records temperature along the way, so temperature at each depth is known based on the amount of time passed. When the bottom is reached, the thread is cut (and the weight stays at the bottom of the ocean). T-Beam is using them to measure temperature in between the set T-Beam profiling stations because it can be launched from a moving ship.

An XBT unit with weighted head and thin copper thread at tail.

And that may be just about all you’ve ever wanted to know about ocean thermography!

– Judy Lemus, Falkor

The Tasman Tidal Dissipation Experiment // Supported by the National Science Foundation

Revelle: Wellness In the Waves

Matthew "Muscle Man" Alford busting out some pull-ups. Credit: Julia Calderone.

Matthew “Muscle Man” Alford busting out some pull-ups. Credit: Julia Calderone.

There’s a science to staying healthy on a boat that dishes endless supplies of savory meals, pastries, snack foods and deserts. We’re confined to a 284-foot ship with a daily commute of scaling a flight of stairs and walking a few dozen feet to our workspaces. This, combined with a typical 16-hour workday, makes an exercise routine a necessary part of the day.

For this reason, Matthew Alford spearheaded a fitness challenge—not only for our physical health, but for our mental wellbeing as well. Before we set sail, he emailed the team to pump us up about daily fitness goals: “For me, ships are like jungle gyms, so I’m going to set a goal of doing 200 pushups, 50 sit-ups and 50 pull-ups every day of the whole cruise,” Alford wrote.

One of the many snack stations on The Revelle. Credit: Julia Calderone.

One of the many snack stations on The Revelle. Credit: Julia Calderone.

Like a champ, he has stuck with this goal and we’ve all been roped into random workout flash-mobs. We’re lucky to have had mostly beautiful, clear weather to hit the decks for some serious sweat sessions. The Falkor has even challenged us to a fitness contest.

And not that it’s a real competition or anything, but when it comes to competing against the R/V Falkor, we’re winning. Just saying…

—Julia Calderone, The Revelle

 

The Tasman Tidal Dissipation Experiment//Supported by the National Science Foundation

Falkor: Chlorophyll is Key to the Biological Oceanographer

This week Pete and I started doing our experiments with water collected from the CTD profiles. We are using the water to conduct chlorophyll measurements, particular organic matter contents, nutrient samples and incubation experiments. All the data that will be collected from our water samples will help us to piece together the possible mixing that is being caused by the internal tides.
Danielle filtering

Danielle Mitchell filtering water samples. SOI/Judy Lemus

Staying Focused and Organized

The chlorophyll samples that have been taken will all be processed on board using a fluorometer, whereas the other samples require a mass spectrometer which will be sort out at IMAS when we get back into Hobart. Until then, hundreds of litres of water will be filtered to capture the phytoplankton in the water and then frozen so that they do not degrade while we are at sea. In between all the filtering and processing of water, it is imperative that Pete and I stay organized so that we know what samples are what. This generally involves labeling sample containers and creating data sheets. These methods will also assist the helpers that will be called upon at IMAS to process samples later on.

Properly labeling samples is a critical (and sometimes relaxing) task for field work. SOI/Danielle Mitchell
Samples for filtering

The filtering rig has been kept busy filtering lots of water samples.  SOI/Danielle Mitchell

In addition to all the water samples and filtering that we have been doing, we also set up a flow-through fluorometer, which uses the water intake from the ship (ships take in seawater to cool their engines) to identify any changes in chlorophyll at the surface. This particular fluorometer was meant to be attached to the small CTD package. However it didn’t fit in the CTD frame which meant we had to find another use for it, in our case a flow through measurement that will give us continuous surface data.

The Fluorescent Ocean

Fluorometry is a very useful tool for biologists interested in phytoplankton.  Chlorophyll, the molecule inside the plankton that absorbs light for photosynthesis, will give off light at a distinct wavelength (fluoresce) once it absorbs a photon of light.  When chlorophyll is extracted from the phytoplankton using alcohol, a standard fluorometer quantifies this fluoresced light, thus giving a good approximation of the amount of phytoplankton that was in the sample. The flow-through fluorometer provides an even better measurement of phytoplankton biomass because it measures the absorbed light energy that is actually is transferred into the photosynthetic machinery of the cell (a process called electron transport) and gives an estimation of how well the intact phytoplankton cells are photosynthesizing in the ambient surface water. We will be using this data along with the data gathered from the standard fluorometer to determine if the internal tide has an effect on the phytoplankton biomass. As discussed in a previous blog, changes in phytoplankton biomass may be due to nutrient mixing and availability, or even mixing of phytoplankton themselves throughout the water column.

Another use of fluorescence: NASA uses fluorescence detecting satellites to create images of global phytoplankton distributions (seen in red). NASA

Work and PlayMornings on the ship are usually dedicated to science. However, the afternoon usually involves social based activities. For instance, the ship has over 200 movies to watch not including the movies that people bought on their hard drives, or even the odd board game like Cranium or Settlers of Catan. I was also able to help some of the crew members change bike tires. Needless to say, there always something to do or someone to speak to on the ship no matter what time of the day it is!

– Danielle Mitchell (w/Judy Lemus), Falkor

The Tasman Tidal Dissipation Experiment // Supported by the National Science Foundation

Revelle: Mooring’s Back!

Eric Boget, Brett Hembrough and Paul Chua prepare to hook and tag the approaching buoy. Credit: Julia Calderone.

Eric Boget, Brett Hembrough and Paul Chua prepare to hook and tag the approaching buoy. Credit: Julia Calderone.

Most research cruises leave their moorings in the water for months or years, but not these guys. They’re recovering a mooring they just deployed seven days ago. After it’s back on deck, they’ll pull off the data and will re-release it again in a few days. All in the name of science!

The instruments on this mooring have been gathering data for seven days at a unique hill on the Tasman slope, which we’re calling “the bump” (more on this later). The team has been actively profiling this area with the CTD for days, and they are thrilled to get a first glimpse of this data to add to the analysis.

 

Jonathan Nash inspecting the acoustic releases, which tether the mooring to the anchor. Credit: Julia Calderone.

Jonathan Nash inspecting the acoustic releases, which tether the mooring to the anchor. Credit: Julia Calderone.

Recovering a mooring is not much different from lassoing an animal. Except this “animal” weighs thousands of pounds and can be several miles long. First, they release the entire mooring from the anchor that tethers it to the bottom of the ocean by sending a unique encoded sound pulse to the “acoustic release”, a super-strong link that holds the mooring to the anchor. This audible passcode, sent from the ship (potentially from miles away), commands the release to pop open and relinquish the line, sending the entire package to the surface. A beacon at the top of the mooring pings its location via satellite for tracking as it ascends. Since this mooring was 2000 meters deep, it took about 30 minutes to rise to the surface.

Once the buoy surfaced, the captain, his crew and our chief scientist, Matthew Alford, spotted the mooring’s buoy by eye. Had it been night, they would have used its satellite transmissions and flashing lights to locate it in the dark. The Captain then navigated the boat to glide just to the side of the package without letting its trailing tail of instruments get pulled under the ship and tangled into the ship’s propellers. The mooring crew, waiting patiently aside with hooks and tag lines, pounced and wrestled the thousand-pound buoy around the side of the boat as it approached. Then they slowly and deliberately pulled hundreds of meters of line in and removed each of the instruments, one by one. Over the next few hours, the data will be downloaded, processed and analyzed to get a first glimpse at some amazing underwater waves. Stay tuned.

—Julia Calderone, The Revelle

 

The Tasman Tidal Dissipation Experiment//Supported by the National Science Foundation

scripps oceanography uc san diego