Category Archives: Blog

Back to the barn // TTIDE ends in Hobart port

The R/V Revelle has headed “back to the barn” and has just docked in Hobart, Tasmania.

Back to the Barn. Photos: Thomas Moore

Back to the barn. Photos: Thomas Moore

All hands on deck are now in the usual post-cruise full-court-press to get all the remaining scientific gear packed, off the ship, and into containers for the return journey.

It’s a morning of mixed emotions, we’re all happy to be back in port and heading home but it’s bitter-sweet to be leaving behind the R/V Revelle, her Captain and crew, and our days on the Tasman Sea.

Albatross of the Tasman Sea. Photo: Thomas Moore

Albatross of the Tasman Sea. Photo: Thomas Moore

 

Good morning from the Tasman Sea

A special dawn for the R/V Revelle off southeastern Tasmania.  Photo: Thomas Moore

A special dawn for the R/V Revelle off southeastern Tasmania. Photo: Thomas Moore

Good morning! The daytime watch awoke to a spectacular sunrise here aboard the R/V Revelle, stationed about 40 kms off southeastern Tasmania.

All 14 moorings are aboard and we have been settling in for the final few days of ocean observations. We have 48 hours left on this final leg and the TTIDE team is making as many “yoyo” and “towyo” operations as we can.

T-TIDE student profile: Madeleine Hamann

PhD student Madeleine Hamann from the Scripps Institution of Oceanography is aboard the R/V Revelle for the T-TIDE leg 3 cruise and here she talks about her work and how studying math, science, and engineering has opened up a world of opportunity for her.

The final countdown

The Final Countdown

Albatross fill the air, Tasman Island in the distance - the location for the TTIDE southern moorings.  Photo: Thomas Moore

Albatross fill the air, Tasman Island in the distance – the location for the TTIDE southern moorings. Photo: Thomas Moore

It’s the second weekend out here on the Tasman Sea for the TTIDE leg 3 crew aboard the R/V

Revelle. Today we are pushing hard to finish recovering all four remaining moorings still in the water.  If the team can make all that happen before darkness falls tonight that will keep the TTIDE project ahead of schedule and give the scientists extra time to conduct “yoyo” and “towyo” operations – filling important gaps in our view of the internal wave energy pulsing across the Tasman Sea.  There are only a few days left until the R/V Revelle steams “back to the barn” and for all aboard it’s starting to feel a bit like the final countdown.

Dawn broke gray and chilly but the howling westerly wind and the short, steep windswell it generated has mercifully laid down.  It was a great way to start the recovery of TTIDE “M4”, a 2300 metre tall mooring designed to capture the energy of internal waves breaking in the shallowing waters of the continental slope using two highly specialised McLane profilers.

The McLane profilers are “wire-crawlers”, programable robots that climb and descend the mooring line over and over and over again, one million metres worth of travel in every one of their large internal lithium battery packs.  These profilers come jammed with an array of instruments that

A McLane profiler breaks the surface.  Photo: Thomas Moore

A McLane profiler breaks the surface. Photo: Thomas Moore

measure pressure, temperature, salinity, and most importantly current velocity at a finer scale and across a longer vertical reach than any other tool in our oceanographic toolbox.

The McLane data are invaluable, they are costly acquire, and each profiler runs on hardware and software that takes great skill and experience to operate.  The McLane profiler, often abbreviated as “MP” in casual conversation on the back deck, is the star of the show and everybody quietly anticipates the outcome each time one of these yellow beasts breaks the surface of the sea under the tug of our winches.  Did the wire-crawler survive the pressures of the deep and what data will it hold for the TTIDE team?

Science, caught fresh from the sea

The MP’s have indeed brought a data harvest, fresh from the sea.  As moorings have been brought onboard the attached instruments are cleaned and logged before TTIDE team members get busy up forward in the analytical labs extracting the data onto a dizzying collection of hard drives.

the first analyses of MP data is underway

the first analyses of MP data are underway

Time is always short aboard ship but TTIDE scientists have started to look at the new MP data in the past 24 hours, building the initial analyses of what an underwater robot has learned from crawling a mooring wire for many months deep under the surface of the Tasman Sea.  This first look at the MP data shows the clear fingerprints of the daily tide, lunar cycle, and the passing of swirling mesoscale eddies as they swept over the slope 20 kilometres or so off St Helens, Tasmania.

When the TTIDE scientists finally return home* they will bring all the fresh science they have caught into their data kitchen and cook up a better understanding of our earth, climate, and ocean.

Thomas Moore, for the TTIDE team

Prof. Matthew Alford works on a MP back in the ship's lab.  Photo: Thomas Moore

Prof. Matthew Alford works on a MP back in the ship’s lab. Photo: Thomas Moore

* “home” means many things for the diverse TTIDE team, made up of experts from the University of Minnesota – Duluth, the University of Alaska – Fairbanks, Oregon State University, the University of Washington, and the Scripps Institution of Oceanography.

A needle in a giant haystack at the bottom of the sea

Dmitry Brazhnikov, Josh Manger, June Marion, Amy Waterhouse, and Matthew Alford celebrate with an ADCP selfie

Dmitry Brazhnikov, Josh Manger, Bex Dunn, Amy Waterhouse, and Matthew Alford celebrate with an ADCP selfie

If losing an expensive package of scientific instruments on the bottom of the ocean is a painful fact of life for the sea-going oceanographer then finding something that was once lost is a glorious moment.  

The TTIDE leg 2 team was unable to bring home one of their bottom mounted ADCP’s, lost somewhere off the northeast of Tasmania in about 80 metres of water.  “ADCP” is an acronym for Acoustic Doppler Current Profiler, an instrument capable of measuring the velocity of ocean currents from the shelf floor to the surface.  But something unexpected and disastrous occurred and a recovery float, the ADCP’s lifeline to the surface, became separated from its companions. 

So for two nights on TTIDE leg 3 the R/V Revelle patrolled the last known position of the lost gear, dragging heavy trawl wire and grapples in a crisscross pattern.  Last night at 2am, after many hours of searching, suddenly the tension on the line monitor jumped to over 1000 pounds.  Was this just a spike in wire tension, a temporary snag?  No, the tension was steady and that meant the TTIDE team had caught something significant.  “You don’t imagine that you can actually collect this thing that has a tiny footprint of about 20 metres on the bottom,” said Amy Waterhouse, lead scientist at the time of the recovery.

Night ops on the R/V Revelle.  Photo: Thomas Moore

Night ops on the R/V Revelle. Photo: Thomas Moore

If snagging the ADCP was impossibly improbable getting it back to the surface and on deck safely was potentially perilous.  In what condition and orientation would this mess of anchor, grapple, wire, and technology arrive aft of the R/V Revelle?  Slowly, over a operation carefully executed by the skillful resident technician Josh Manger, each part of the tangle was brought aboard step by step in the dark.  Finally, two hours later the ADCP was lying on the deck surrounded by a happy bunch of TTIDE crew celebrating out on the Tasman Sea at 4 in the morning.  

The R/V Revelle quickly set course south for the next task, the recovery of mooring “T7”.

Storm Force

As dawn broke off Tasmania’s Freycinet Peninsula the TTIDE team and crew of the R/V Revelle faced an increasingly angry sea and a challenging 72 hour weather forecast.  Strong westerly winds, gusting up to 54 knots, make for demanding working conditions on the back deck.  After a brief meeting on the bridge a decision was made to temporarily cancel mooring recovery operations and switch efforts into “yoyo” mode.

Storm force winds whip the Tasman Sea off Tasmania.  Photo: Thomas Moore

Storm force winds whip the Tasman Sea off Tasmania. Photo: Thomas Moore

“Yoyo” is a term that refers to mounting a large number of scientific instruments on a specialised frame and hanging that frame off a powerful and capable winch system.  This package of instruments is slowly lowered to great depth and then brought back to the surface taking measurements of the ocean’s properties.  The up and down motion of the instrumentation package on the wire gives “yoyo” operations their name.

With great patience each up and down dip of the frame, known as a CTD cast, adds one snapshot of information about the internal state of the sea.  Ideally we will stay on station for at least 24 hours to capture an entire tidal cycle, the beating pulse of the internal waves the TTIDE team is chasing.

With our CTD casts underway we have one eye on the winch and one eye on the weather.  When we get a break in the storm force winds it will be back to our line of moorings to recover “T7”.

Thomas Moore, for the TTIDE team

Matthew Alford, Captain Dave Murline, Eric Boget, and Gunnar Voet discuss weather options on the bridge of the R/V Revelle.  Photo: Thomas Moore

Matthew Alford, Captain Dave Murline, Eric Boget, and Gunnar Voet discuss weather options on the bridge of the R/V Revelle. Photo: Thomas Moore

In the lee

Captain Dave Murline of the R/V Revelle keeps eyes out for a mooring rising to the surface.  Photo: Thomas Moore

Captain Dave Murline of the R/V Revelle keeps eyes out for a mooring rising to the surface. Photo: Thomas Moore

Down here in the “roaring forties” Tasmanians have a saying for their typical weather patterns, “four seasons in one day”.  It can be sunny and calm one moment and blowing a gale the next.  After the R/V Revelle’s first few days of relatively calm weather we have what looks to be multiple cold fronts on the way, along with the roaring westerlies they can bring.

Luckily the TTIDE team and the R/V Revelle have been working like a well oiled precision timepiece and we are on schedule, the back deck currently abuzz with winches and gloves hauling in our seventh mooring for this the third and final TTIDE leg.  Our promptness has also been a blessing as it has put us at our series of northern shelf moorings, up in shallower water near the coast of Tasmania and somewhat in the lee of the gale gusting to 45 knots.  

In the lee of Tasmania the roaring forties have less “fetch” – the distance travelled by wind across open water – saving the TTIDE mooring recovery crew from having to perform their often tricky and sometimes dangerous work on a deck pitching and heaving in mountainous swells. 

A 48" orange ball of syntactic foam - the top of mooring T3 - floats at a distance in a wind-blown Tasman Sea.  Photo: Thomas Moore

A 48″ orange ball of syntactic foam – the top of mooring T3 – floats at a distance in a wind-blown Tasman Sea. Photo: Thomas Moore

Mooring “T3” is coming in across the blocks as this post it being typed and with luck and skill the TTIDE team will wrestle back from the bottom four entire moorings today.  A challenging feat – wish us well.

– Thomas Moore, for the TTIDE team

Undersea Gliding

Albatross, a glider of the southern skies. Photo: Thomas Moore

Albatross, a glider of the southern skies. Photo: Thomas Moore

The ocean we are trying to better understand is always moving and changing, varying across great distances and depths as well as the passing days and seasons.  It’s impossible for us to be everywhere all the time but with the help of special programmable gliders TTIDE scientists are learning more.

Gliders are a relatively new type of instrument platform, essentially ocean floats with wings and a robot brain, and they fill important gaps in our TTIDE shipboard and mooring observations.  This is a very capable ocean science platform, some versions of which have been developed in house at the Scripps Institution of Oceanography, that can turn and change both their horizontal and vertical position within the water column. Gliders can literally fly through the sea and be programmed to record data like ocean temperature, salinity, velocity, and sometimes other more biologically important quantities such as oxygen levels and chlorophyll.

Bex Dunn with one of the two recovered gliders.  Photo: Thomas Moore

Bex Dunn with one of the two recovered gliders. Photo: Thomas Moore

Another virtue of the glider platform over fixed moorings is that they regularly return to the surface and communicate back to base at Scripps.  This allows very recent ocean measurements to be seen by an operator who then has the option to reprogram the glider and adapt to changing priorities.  Oceanographers call this “adaptive sampling”.

We have so far successfully recovered two of these wandering ocean robots and their data will help provide a baseline for TTIDE scientists to better understand the complex dynamics of the internal wave pulses that cross this stretch of the Tasman Sea.

 – Thomas Moore, for the TTIDE team

Listening to the ocean and talking to the deep

Words and photography: Thomas Moore

Tasman Sea
Latitude – 44.5 degrees south
Longitude – 152.3 degrees west
Ocean Depth – 4768m

Screen Shot 2015-02-02 at 1.57.22 PM

The TTIDE team is back aboard the R/V Revelle and we are again plying the fickle waters of the Tasman Sea.  This is the final cruise in our latest venture to better understand ocean mixing and how internal waves can influence both climate and the ecosystems that support marine life and our communities and industries back at home.

On the maiden cruise our team, a capable mix of veterans and first time volunteers, deployed fifteen moorings, towering strings of scientific instruments thousands of metres tall supported by giant floats and anchored to the seabed by hefty weights.  Like 15 giant balloons tethered sky-high in a watery atmosphere, our moorings have swayed in the ocean currents for over a month recording characteristics like temperature, salinity, pressure, and the speed and direction of ocean currents.  The TTIDE moorings have been listening carefully to the ocean for a long time but all that they have learned will stay a secret unless we can get them back safely aboard the Revelle and in one piece.

Matthew Alford and the TTIDE team attempt to release mooring A1 using one of their 3 deckboxes.

Matthew Alford and the TTIDE team attempt to release mooring A1 using one of their 3 deckboxes.

Hello, are you still there?

On our first day the Revelle steamed from Hobart, Tasmania roughly one third of the way to New Zealand to arrive at location “A1”, the tallest and most complicated of all our moorings at 4727 metres worth of wire, engineering, and technology.  Mooring A1 is designed specifically to measure the energy in the beam of internal waves rolling towards Tasmania before that beam can be influenced by the bottom when it eventually travels into the shallower waters of the slope and shelf.  Here the water is almost 5km deep and therein lies our first challenge.  To get the mooring to rise to the surface we must “talk” across this underwater distance with sound waves, literally commanding it to return from the bottom.  What if we speak but nobody is listening?  It’s always the first unknown in a mooring recovery operation and on “A1” the TTIDE team had some anxious moments from the very start.

We carry aboard Revelle three different options for acoustically communicating with the mooring releases, the mechanical “hands” that grasp the bottom anchors on the sea floor.  Each of these three communication units sends acoustic messages from the surface and receive back responses from the release units, or at least that is what is meant to happen.  For much of the first operational hour of our twelve day cruise the science team sat huddled around the acoustic unit at first expecting, later hoping, and finally praying that we’d get a response.  “Hello, are you still there”?

Mooring release failure is one of the worst situations a sea-going oceanographer can encounter.  After sometimes years of proposals, funding, planning, construction, and deployment you now have a precious cargo of pricey scientific instruments and priceless oceanographic data that sits silent on the ocean floor – unresponsive, unmoving, stuck out of reach.  If you talk to the deep but the deep is not listening you have but one extreme measure left to consider – dragging.  Nobody wants to drag for their mooring.

Jon Ladner keeps an eye out for the top float of mooring A1

Jon Ladner keeps an eye out for the top float of mooring A1

Dragging for a mooring involves streaming many kilometres of heavy cables, weights, and hooks behind the ship in blind hope that you can literary rake the mooring off the seafloor and force it to the surface.  It’s an arbitrary and highly destructive option reserved for the most desperate of situations.  Luckily for the TTIDE team, after the failure of our first two acoustic units, we were all very happy to get a response from the mooring release on our third and final backup unit.  A few minutes later there was immense relief when the top mooring float finally broke the surface about 300 metres away from our position.  Now the team could get cracking bringing in over 4700 metres of wire and some sixty odd scientific instruments.

A day on the wire

Getting a 4700 metre mooring to the surface is just the start of the job and it took all the daylight hours we had on hand to get all the bits of wire rope, floats, and scientific instruments back aboard the Revelle. 

Working the back deck

Working the back deck

The first day of mooring recovery on the back deck of any research ship is always somewhat unpredictable as a new group of veterans and volunteers gets into the rhythm of wire and winch.  For our first day we were blessed with great weather, relatively calm seas, and a team that immediately hit their stride.  Effective teamwork is the most vital component for success on a cruise with such an ambitious agenda of recovering 15 moorings in a short period of time.  The operational tempo for TTIDE leg 3 over the next 11 days or so will necessarily remain extremely high for the whole crew and science team.

It was wonderful for us all to get mooring A1 back from the depths and onboard today.  The instruments are cleaned and loaded into the labs aboard Revelle and in a few days all the data should be downloaded.

The deep does sometimes talk back when called upon.

TTIDE leg 3 team, aboard the R/V Revelle over and out for now.

– Thomas Moore, for the TTIDE team

Eric Boget beams as another bit of valuable scientific instrumentation arrives safely on the deck of the R/V Revelle

Eric Boget beams as another bit of valuable scientific instrumentation arrives safely on the deck of the R/V Revelle

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