From the Chief

 
Weekly report #7 – Jan 12, 2017
Rolf Sonnerup

Two weeks into Leg 2 of GO-SHIP P18 2016/17, we’re at 47° 30’S, and the weather is … NICE!  Sun rises at 6:20, and sets at 9:45.  

Not that we haven’t seen some weather.  We had a 48 hour blow (25-30 kts) over the 8th and 9th that tested our deploy / recover skills on the forward winch.

We have been occupying stations more or less on schedule, losing time in poor weather, clawing it back in good.  In the meantime, ship’s engineers disassembled the aft winch‘s brake mechanism.  They discovered a flaw similar to your throwout bearing failing to fully re-engage your clutch.  Once re-assembled, the rear winch passed repeated 3000# load tests in and out of the water.  Emboldened, we planned a switch to the aft winch the following day.

It was not to be.  Later that evening, the wire / termination (fwd winch) started showing signs of trouble, including alarms from the deck unit.  While we puzzled over this one, a water supply line ruptured in survey tech Alyssa Pourmonir’s stateroom, flooding her belongings.  Next, a fire alarm.  Not a drill.  The CTD was at 3000 m, with orders to bring it aboard immediately.  While we assembled at our muster station, Commando K. McTaggart tripped bottles on the ascent.  Nothing else matters.

In the end, the source of the fire alarm was discovered: water tripped the smoke detector in Alyssa’s room. Commando, ahem, Commander McTaggart seized the opportunity:  “Jeff (ship electronics tech) is awake now anyway, he may as well stay up and reterminate this thing”.  And so it was.  Special thanks to Jeff Hill, and to operations officer Brian Elliot, who, on 6 minutes’ sleep, was confronted with lively, if not hysterical, accounts of submerged laptops and personal effects, a real fire alarm, and a surprise request for a midnight winch swap. He handled these with aplomb, and in pajamas, no less.

We have been using the aft winch now for three days. We’ve been advised against throwing a retirement party for the tugger.  No need to tempt the winch gods.

Our schedule provides for half-degree spacings to 70°, or maybe even 72°S (depending on topography) with just under four weather days’ cushion.  Ice conditions are improving.  Our official arrival date in Punta Arenas has now been posted – Afternoon of the 4th of February.

Having verified that somebody actually reads these, we clarify:  XCS is shorthand for “eXpendable Chief Scientist”. Although one XCS deployment per cruise would do wonders for morale, and may improve the job market, I wonder if it’s really true that “The chief scientist goes down with the ship”.  We learned this at drills today.

For the weekly “We miss Andy, and how” column, a special congratulations and thanks to Paige ‘Float Lady’ Logan.  Paige is doing a great job at the very important task of running salts during part of her watch.  We promise to come get her next time there’s a fire alarm.

Box score:  P18 Leg 2, Week 2
26 CTD stations occupied
6 Argo/SOCCOM floats deployed
4 drifters deployed
Currently at 47°30’S
Ice cream still in good supply

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Weekly report #6 – Jan 5, 2017
Rolf Sonnerup

We are now one week into Leg 2 of GO-SHIP P18 2016/17.  About half of the scientific staff have changed hands.  Sarah Purkey and I thank Brendan Carter and Annie Bourbonnais for remaining aboard to ease our transition, and in particular for leaving us with a crew of scientists in excellent spirits.  Weather must’ve been great.  One person who is sorely missed is Andy Stefanick, Jedi Master of the CTD and salt analysis, who returned home from Easter Island with a sprained ankle.

After a bit of back and forth, including a visit to the Hanga Roa Harbormaster with our Chilean observer and translator, we did not gain clearance to conduct operations within the Chilean EEZ near Easter Island.  Also, our departure date from Easter Island was delayed by two days – one awaiting a 3rd engineer filling in for a badly injured crewman, and a second day awaiting a new motor for the ship’s incinerator.  Basics before science.  During the wait, Sarah, Jay Hooper and Kristy McTaggart brainstormed a worksharing arrangement to cover, at least partially, the myriad of responsibilities handled by Andy Stefanick. 

We departed mid-morning the 30th of December, Destination:  P18 station 116, located at 23° 54’ North, 103° West, adjusted six miles north from its planned location to stay well clear of the Chilean EEZ about Easter Island and Sala Y Gomez.  We occupied 116 at 7 pm local time – concurrent with the ship’s new year’s eve party in the library.  Happy New Year, we’re underway. 

To stay clear of the EEZ, and occupy a more or less meridional line, we proceeded to the Southwest to station 117 at 24° 30’S, 102° 20’W, and stations 118 through 124 from 25° to 28° S along the 101° 30’ W meridian, a line as close to tangent the EEZ as comfortable.  We returned to the 103° W line via stations 125 at 28° 30’S, 102° 20’W and the slightly adjusted station 126 at 29° 6’S, 103° W.

These stations were occupied without incident, and we continued as planned (half degree spacings) along 103° W, making up time due to the favorable weather and seas.  We had some issues on Jan. 4 at stations 129 and 130.  Both conductivity sensors and all cabling on the lower end cap were swapped out for a total delay, including aborted (then repeated) casts, of ~five hours, before we were back in business. 

This delay was opportune for the ship’s engineers, who conducted yet another test of the aft winch.  They had been troubleshooting this winch nigh-daily in Easter Island and, sadly, were frustrated again.  We continue to operate with the forward winch and are rehearsing our timings and roles on deck with the tugger (for centering the CTD/rosette on the Brown’s sliding platform) to hasten our recoveries and assure safety in the seas to come.  Thankfully, the forward winch is working flawlessly.

Our current station timings provide for half-degree spacings to 72° S, but with only just under four weather days’ cushion. 

Depending on ice and weather conditions, an XCS section has been proposed from 103
°W to Thurston Island (72°S, 201°36’W, so 24 mi. to the East), to capture boundary flow from the East.  To conserve fuel and time, the XCS section will be conducted via small boat by Dr. Sonnerup and may, at the discretion of the co-chief, be limited to one-way. 

Welcome aboard to new scientists for Leg 2
Cathy Garcia (Genetics)
Yves Plancherel (3H-3He and Rare Earth Elements)
Bethany Kolody (iTag genetics)
Myself (Chief Sci.)
Sarah Purkey (Co-Chief Sci.)
Emma Pontes (O2)
Chris Langdon (O2)
Conrad Luecke (CTD watchstander)
Paige Logan (CTD watchstander)
Rachel McMahon (CFC/SF6 analysis)
Andrew Collins (dissolved inorganic carbon)
Charles Featherstone (dissolved inorganic carbon)

And a special welcome to our Chilean observer and sample cop/genetic sampler extraordinaire:  Javiera Veloso, who is assisting our Genetics programs as part of the requirements for her undergraduate degree in marine biology at Valparaiso University.

For Leg 2 we have one new project aboard – iTag® - genetic fingerprinting of South Pacific water masses as part of Bethany Kolody’s pHD dissertation.

In all, during week one we transited to the 103° W Meridian, occupied 20 full-depth CTD stations, deployed four ARGO floats, two SOCCOM floats, and three drifters.  The weather continues to be very nice with (mostly) calm seas so we’re keeping our fingers crossed for, ahem, a peaceful occupation of the 40s and 50s on the P18 line, and a full two-way section to Thurston Island. 

As a follow up to Weekly Rept. #4, our primary concerns going forward are the weather, the continued viability of using the forward winch under adverse conditions, ice cover South of 68° S, and the limited zone within the Chilean EEZ where we do have clearance (Fig. 1).  The zone permitted, part of earlier plans to occupy the P17E section, involves either a substantially longer transit into the Straits of Magellan, or conclusion of all underway measurements just beyond the Chilean EEZ.

Figure 1.  Map of the Chilean EEZ in the South Pacific Ocean.  The grey rectangle near 53.5° is the region within the EEZ where we have clearance to conduct measurements.

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A map of our section, with the yellow arrow highlighting what we’ve done this week.

Weekly report #4:  Onward!
Prepared 12/18/2016

We're on fire!  (Figuratively, of course.) 

We are at the tail end of a third week in a row of efficient southward progress with data from another 29 stations to show for our hard work.  These were somewhat deeper (i.e. longer) stations with an average depth >4000 m crossing the Bauer and Roggeveen Basins.  We owe our solid progress to continued laudable efforts from the scientists and crew, fair weather, and no small amount of luck.  We are still on pace to have an efficient transit to Easter Island.  If all goes to plan, next week's update will have pictures of stoic stone Moai statues and leg 2 folks getting settled.  That will be my last update, and Rolf Sonnerup will take over from there.

In addition to our normal duties, we are busy documenting the analyses and troubleshooting that went on during leg 1.  While this information will ultimately be included in the P18 project report compiled at the end of leg 2, our goal is to gather as much of this information as possible now while all of the leg 1 participants are still on hand. 

We are also excited and gratified to be receiving data from the scientists operating the floats we deployed several weeks ago.  It sounds like those measurement programs are off to a good start.

Ocean ventilation on leg 1 vs. leg 2

P18 connects the oxygen deficient zones of the Eastern Tropical North Pacific with the formation region for Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW) in the Southeastern Pacific sector of the Southern Ocean.  AAIW sits at the base of the thermoclines of the Southern Hemisphere and is noted for being unusually fresh (i.e. a salinity minimum).  SAMW is found above AAIW in a portion of the ocean that is weakly stratified (i.e. low potential vorticity).  Both water masses are noted for their comparatively high oxygen concentrations, and the two water masses have similar densities to the oxygen deficient waters on the north end of P18.  The juxtaposition of these high oxygen water masses to the south next to low oxygen water masses to the north makes for a dramatic transition at about the latitudes we are currently crossing.  The two plots below—highlighting this transition—jumped out at us while we were comparing CTD data against the measurements from decades past.




Top: a section of O2 concentrations as measured during the 2007/2008 occupation about a decade ago.  The low oxygen water masses to the north abruptly transition to higher oxygen water masses to the south near where we presently are (the blue arrow labeled "Ron Brown").  Bottom: this transition can be seen in our CTD data as well as intrusions of high-oxygen (brightly colored) fresh (low-salinity) waters in the most recent casts (notably the most recent two stations with lines on the left side of this plot).


Looking ahead


A map of wave heights along our section (from windytv.com).  Notice the placid blues across leg 1 and the band of red across the southern end of the P18 line.


We have had a good set of weeks, but, as ever, we are anticipating challenges as we look ahead.  Here are a few things on our radar:
1.   Whether leg 2 will have enough time to cross the Southern Ocean: these last three weeks have helped us to recover from the delays of the first week.  However, it is difficult to predict how much time leg 2 will require crossing the Southern Ocean.  The only surety in that region is that there will be bad weather at some point.  The question is how bad it will be and for how long.  The map above of wave heights might give a sense for why I am concerned.  This forecast has been similarly calm on the north end of P18 and restless on the south for at least the last month.  It is impossible to safely deploy our equipment and collect seawater when winds and waves get strong enough.
2.   The aft winch: we've put an additional 80+ casts on the forward winch, and the wire on that winch has been used on previous projects as well.  This leaves leg 2 with one winch in need of repairs and one with a wire that has been extensively used.  We are hoping the repair efforts go well in Easter Island, and that the parts being flown in allow the aft winch to be used (thereby avoiding relying on the tugger in rough seas).
3.   Chilean clearance: We had been assured our research in the Chilean EEZ would be approved, but we didn't get confirmation that we were good to go until very recently.  We were understandably concerned given our experiences off Mexico.  However, now we're cleared to continue our leg 1 work into the EEZ, which we'll enter late on Tuesday December 20th.  Kudos again to our contacts in the State Department for helping us to push this issue forward.

Summary
It has been another great week.  We're beginning to wrap up leg 1 activities and working to lay the groundwork for leg 2.  A lot of work remains between us and port, but the end is in sight, and just in time... we've run out of milk and we're down to our last jelly beans.

Sampling at sunset... photo from DOM analyst Mari.



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A map of our section, with the yellow arrow highlighting what we’ve done this week.


Weekly report #3:  Across the Equator.
Prepared 12/12/2016

We have had another productive week.  We crossed the Equator and started our journey across the Southern Hemisphere, completing 33 stations and the rest of our high-resolution Equatorial work in the process.  We’ve had very few delays this week, and no significant ones.  We are making good time, and are on track to make it far enough South to have a short and efficient transit to our end-of-leg-1 port call on Easter Island.

We are now on the diagonal that takes us from the 110°W meridian to the 103°W meridian.  As I write this we are on one of the pair of shallower (~3000 m) stations directly over the East Pacific Rise.  The East Pacific Rise is a mid-ocean spreading ridge, a massive underwater feature of the Earth’s crust that has fascinating physical and geochemical interactions with the ocean above it (it can be seen as a lighter blue band in the map above).  Some of our analysts are specifically aiming to measure the signatures of these interactions.  The P18 line angles NW/SE between 5° and 10° S to capture this feature while still resolving the deeper ocean basin between the East Pacific Rise and the Peru-Chile Trench.  There will be a long set of deeper stations as we come down off the Rise and continue South into that basin in the remaining two weeks of leg 1.

One exciting bit of news is that we will have a Chilean observer joining us in Easter Island.  The observer is trained as a marine biologist at the Universidad de Valparaíso, and we look forward to having her input and company.

Equatorial Currents




SADCP measurements of the eastward current velocities (top) between 8° and 18°N and (bottom) around the equator.  The white areas are where there weren’t strong enough echoes to make a reliable measurement.  The alternating deep and shallow readings on the top plot hint at what time of day it was when the boat was making the measurements.  The deeper measurements are from the day when many small organisms go down to the darker depths to hide from predators.  At night, the critters return to the surface to feed on even smaller organisms, so the SADCP doesn’t have anything good to bounce sound waves off of at depth.  Credit for this data belongs primarily to Jules Hummon who leads the SADCP data collection effort.


As mentioned in the last update, the narrow band around the Equator has strong and unique currents that are possible due to the disappearance of the Coriolis force at the boundary between the Northern and Southern Hemispheres.  Our shipboard Acoustic Doppler Current Profiler (or SADCP) can measure these currents directly by pinging the ocean with sound waves and measuring the frequency (pitch) of the echoes.  The echoes bounce off of things caught up in the currents (mostly small plankton).  Two plots are provided for comparison, both showing the eastward current versus depth across a range of latitudes.  The top one is from further north and shows a typical current structure.  The second plot shows the much stronger and more confused current structure expected across the Equator (0°N on the figure). 

Staying on station while also keeping the CTD rosette package more-or-less directly below the boat as the package sank through the strong and variable Equatorial currents provided an extra challenge for the Brown’s crew.  However, they were successful, and we completed all of our Equatorial work without any significant problems.  The Brown’s crew should also be commended on having recently repaired the ship’s POSMV system in January of 2016.  This system provides accurate position, heading, and velocity information that the SADCP needs to make accurate measurements of the currents.

Shipboard measurement differences


Preliminary measured distributions of total dissolved inorganic carbon (DIC: left panel), and the  increases (red) in DIC relative to concentrations measured during the previous P18 occupation in 2007/2008 (right panel).  The concentration changes shown are relative to the measured DIC in the earlier occupation interpolated onto the same neutral density surface that the water was on when we measured it on this occupation.  These data are brought to you through hard work from analysts Bob Castle and Remy Okazaki.

We’ve begun plotting many of the properties we’re measuring on board and mapping the differences between our measurements and the measurements from decades past.  This is primarily a quality control exercise.  Very large differences between the decades can be a sign of problems with the analysis or data entry, especially when only a single measurement shows the large difference.  Fortunately, the data appear to be quite clean so far. 

Of course the other reason to make difference plots is that we are all very eager to see how the seawater properties have changed since the last time scientists measured the P18 section (even though we recognize the data we are producing are still too preliminary to do solid research with).  As an example, the plot above shows the increase in total dissolved inorganic carbon (DIC) over the last decade on surfaces of constant density mapped back onto a depth section.  We expect to see increases in DIC as the ocean continues to absorb the CO2 that humans are emitting into the atmosphere.  This plot shows the expected increases have continued over this last decade, especially near the ocean surface.  However, finalized fully-calibrated data and a more thorough analysis will be required to accurately quantify how much of this increase is attributable to human CO2 emissions. 

Life at sea



Pictures of Mari (our dissolved organic matter and radiocarbon sampler) enjoying the sunset (left), and Christian (who is currently involved in too many measurements to easily list) making sure none of our hard-earned seawater is going to waste (right).  Brett Walker kindly supplied both pictures.

We’ve been working long days without weekends or vacations for several weeks, and many of us spent weeks more in port in San Diego.  I won’t presume to speak for everyone, but I know I am missing the people, pets, and places that make up my life on land.  Fortunately, we have a brilliant, joyful, and hardworking team of scientists and crew aboard making the long days and nights go quickly and with no small amount of fun.  It also helps that the persistent beauty of the sea, the sky, the sun, and the stars are always just beyond the nearest bulkhead.  For a more about how (and why) we are spending our days at sea, consider checking out the P18 blog.

Summary
It has been a good week for most aboard, and the science and crew team should feel proud of hard work they did through the Equator crossing.  Nevertheless, we are steeling ourselves for another two weeks of focused work and trying not to daydream too much about the island that awaits us at the end of this first leg of P18.
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A map of our section, with the yellow arrow highlighting what we’ve done this week.  We have now emerged from the French and Mexican EEZs (red circles) with a complete set of measurements from each region.  French?  In the middle of that circle we passed through is a small island claimed by France named Clipperton.  It is still the closest land to us.


Weekly report #2:  Down the line.
Prepared 12/05/2016

It has been a pretty good week.  We’ve hit our stride, and have begun completing our station work quickly and efficiently.  We did 29 stations across 13.5° between Nov 28th and Dec 5th.  The Brown has been averaging more than 10.5 kts between stations, our team is sending the CTD-sensor rosette package down to 10 meters off the ocean floor and bringing it back filled with water as quickly as we’d hoped, and we’ve had calm weather and no additional major delays.  Our quick pace perhaps feels faster still due to the ~3700 m average depth of the stations, which is a bit shallower than many of our veteran repeat hydrographers are used to.  We are testing the throughput of our teams various analytical systems despite using a 24 position rosette (vs. the 36 position rosettes that bring back 150% as much seawater).

Our pace southward has slowed somewhat in the last day as we’ve hit the high-resolution equatorial stations.  We’ve doubled the resolution from one station per 30 nautical miles to one per 15 nautical miles within a ±3° window of the equator.  This is to capture the unique mixing, currents, and upwelling found in this narrow band where the influence of the Coriolis force—one of the major factors that governs the movement of water throughout the ocean— effectively vanishes.  The Brown has slowed, but samples are coming aboard more quickly than ever.  This is crunch time for samplers on leg 1, and we’re looking forward to a return to normalcy in 4° south/3 days.  We’ll cross the equator Tuesday around dinner.

Impacts of delays
Our schedule for this cruise has been in flux since early October due to our various delays, but we’ve finally settled on port dates for arriving in Easter Island: Dec. 24th, Christmas Eve.  Leg 2 will depart on the 28th.  We are glad to be able to begin booking flights and planning our time on Easter Island.  Leg 2 should arrive back in Punta Arenas within the first two days in February, 2017.

In light of the delays, we have opted to reduce our double resolution equatorial stations from a ±5° to a ±3° band around the equator.  Also, we are no longer planning any station work on the P17extension that connects the P18 line to Chile.  The increased need for efficiency has decreased our tolerance for delays.  Typically, infrequent short delays can provide the valuable service of allowing our analysts time to collect and analyze more samples per station, especially in high-resolution sampling regions like the equator.  An increased need for efficient progress south may therefore translate into a less-complete record of the seawater brought aboard.  Bongo net casts had been planned to take place during such brief delays, but with the need for efficiency the bongo net program was planned to be scaled back.  (Later the bongo tows were cancelled entirely, see below.)  Similarly, Charles Kovach—our scientist making measurements of the optical properties of seawater who is constrained as to when he can do his measurements by cloud-cover and the timing of satellite overpasses—is now also limited to conducting his work when we are already on station.  In short, the delays have made things harder for most scientists and forced us to be slightly less ambitious.

A section of temperature against depth with contours for dissolved O2 in μmol kg−1.  Profiles go to the ocean floo.  Dots indicate where seawater samples were collected for discrete analyses.  Grey areas represent the ocean floor as it is represented in a low resolution data set. 

Continued science
Aside from fallout from the delays our scientific programs are going as planned.  Our teams are still building up and combing through a wealth of calibration and assessment data.  Samples are piling up for shore-side analysis, and data is beginning to pour into our data files through the hard work of our shipboard analysts and our data manager, Remy Okazaki.  The new (or rather updated) data submission and management software developed by John Bullister is working well for us, which is wonderful because Remy has also absorbed much of the work of the scientists we lost to the delays leaving port (e.g. see the picture below).

The aft winch
As mentioned in the previous report, the aft winch began spooling out in an uncontrolled fashion toward the end of last week.  Our quick-thinking winch drivers saved the package by applying a failsafe break, and our team was able to retrieve the CTD-sensor package intact.  Troubleshooting is ongoing and the Brown’s engineers have ordered several parts for Easter Island that we hope will make the aft winch whole again in time for leg 2.  In the meantime, we’ve been using the forward winch.  While fully functional, the forward winch comes with the added difficulty that it is situated a bit further forward of the tracks we use to move the package in and out of the staging bay.  We’re therefore using a “tugger” or a pneumatic rope-winch, to reposition the package before landing it on the platform.  This is adding a bit more work and a lot more excitement to retrievals.  This strategy is working great for now, but we hope to have a better way of doing retrievals before the project moves into the nearly-permanent winds and high seas of the Southern Ocean (i.e. before leg 2).


Jay Hooper (left) and Remy Okazaki (middle) using the “tugger” to get the package safely onto the rails from the forward winch. 
The bongo nets need to be deployed on a different wire than the CTD-sensor package.  They had previously been deployed off the forward winch.  However, with the aft winch not working and the CTD having been moved to the forward winch, the bongo tows have now been put on hold entirely.  In retrospect, it is perhaps fortunate for Javier (our sole bongo specialist) that the delays prevented him from joining us.

Aft winch silver lining: a complete sensor package
During a brief downtime while the aft winch was being actively troubleshot, our CTD team swapped out the CTD for a spare, and we now have a fully functional package with primary and secondary sensors for conductivity, temperature, pressure, and dissolved oxygen, as well as a reference temperature sensor and sensors measuring optical transmittance, backscatter, and fluorescence. 

Summary

We’re making good time and assessing the impact of the many delays to date.  We’re digging in for a long cruise, and we are hoping for continued efficient southward progress toward Easter Island.  That port date remains distant, but at least it is now solid.


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Weekly report #1:  Clearance extended!
Prepared by Brendan Carter 11/27/2016

We are pleased to report that we are making our way south out of the Mexican EEZ and doing station work as we go.  We were briefly faced with the difficult decision between waiting on station and abandoning the work in the Mexican EEZ.  Some offshore islands make the Mexican EEZ more than twice as thick as the default 200 nautical mile (nm) limit along our track.  This meant that going south to accomplish work outside of the EEZ while we waited was not a good solution, and also that an unusually large amount of station work (~15% of leg 1) would have been lost if we had given up on the EEZ.  Ultimately, we spent nearly a day and a half waiting on station.  We are now slightly behind our ambitious schedule, but relieved to be able to fill in these important measurements of the oxygen deficient zone (ODZ) off Mexico. 

Measuring the ODZ is critical for the GO-SHIP goal of monitoring the ocean’s response to climate change.  It has been hypothesized that the ocean will lose oxygen over time and ODZs will expand under global warming, consistent with many—but not all—simulations of Earth’s future climate.  A portion of our cruise track has been recently identified as a region where the impacts of climate change on interior oxygen may already be detectable.  Deploying instruments to monitor this region and testing this hypothesis with another decade of high-quality GO-SHIP measurements were key objectives for this project.  Several of our instruments and personnel were sent with us specifically in order to capture the unique biogeochemistry in the ODZs.

We have (preliminary) data!  This is a section of dissolved O2 concentrations as measured by the CTD-rosette sensor package .  Black dots are where we have collected seawater for discrete measurements.  The blue band at the top is well-ventilated surface water.   About one hundred meters below are the (deep red) very low oxygen waters of the ODZ.


Path and station work
As noted in the report 0, we initially transited from San Diego to our test station in US waters, and from there headed to the first station offshore Cabo San Lucas at 22.69°N and 110°W.  That first station had an intended depth of 2500 meters.  We waited there for clearance, moving offshore after business hours in Mexico City to take care of ship functions (e.g. making freshwater from seawater).  We quickly began station work after receiving clearance, though we stayed on station for some hours to troubleshoot the CTD-rosette sensor package (see below).  We then moved onshore to collect measurements at a 220 m depth station at 22.87°N and 110°W.  Since then, we have been moving south along the 110°W meridian.  We made the brief northward trip instead of starting at our northernmost station to save a few hours that would otherwise have been spent waiting on station for samplers to finish collecting seawater from the CTD-rosette.  After turning south, we had one more nearshore station in 1250 m of water at 22.78°N.  Our fourth station was at 22.5°N.  Since occupying this station we’ve been transiting south for 0.5° (30 nm) between each station, as we intend to continue to do for most of the P18 line.  We deployed floats on stations 15 and 19 and one drifter on station 13.  We are currently on station 20 at 14.5°N.

This first float we deployed is specially designed to collect data from the ODZs with a gas tension device.  The device will be calibrated using measurements of stable gases being made by Co-Chief Annie Bourbonnais. 

Profiles of temperature, salinity, beam transmittance, and oxygen were collected at every station.  Profiles of fluorescence and backscatter were also collected at the earlier stations.  More than 2000 seawater samples have been collected by our analysts for discrete analyses on the boat and back on land.  Data from discrete shipboard analyses are beginning to trickle in to our central repository from our shipboard analysts.  We expect the floodgates will open soon as our analysts catch up from the abrupt change of pace from prolonged waiting to nearly constantly working.

Troubleshooting
Unfortunately, the ban on research activities in the Mexican EEZ prevented us from more thoroughly testing the CTD-rosette package while we waited.   We therefore spent some additional time on the first station resolving problems with the electronics that manifested on our first cast below 1300 m.  Less than a day of troubleshooting time was required for this and all subsequent package troubleshooting, and the delay allowed time for a bongo tow for coastal organisms and micro-plastics sampling.  After many sensors, cables, and parts were replaced by our experts on board—and after some clean-up of the winch electronics by our shipboard electronics technician—we now seem to have a functional package to at least 3500 m depth. 

One concerning issue has resulted from the new aft winch wire having come from the manufacturer pre-lubricated, contrary to the expectations of the ship personnel when they placed the order.  The wire began to extrude the lubricant during the casts, and did so increasingly as the package got deeper and the wire tension increased.  This resulted in gooey blue lubricant cakes forming up on the block (pulley) that the winch wire spools over.  This lubricant then began to slough off onto the deck and, until we developed means to prevent this, onto the rosette frame.  It is not believed that this lubricant has affected the package in a meaningful way yet, though there is concern over whether it could and whether we would know if it had.  The ship’s crew has gone to lengths to keep this lubricant from affecting the CTD rosette package since it emerged as an issue.  Looking forward, it seems most of the lubricant on the first ~3000 m of cable has already been removed since the caking has significantly abated on recent casts.  However, we fear this problem will return as we begin doing deeper casts.

*A quick update on this before I send this out.  We’ve switched to the forward winch since the aft winch began spooling out in an uncontrolled fashion during a recovery on station 18.  Everyone is safe, the rosette package is intact, and we’re now close to finishing a successful cast on the forward winch.  There will probably be more on this in the next weekly update, so stay tuned.

A storm dodged?
We’ve been watching the track of Hurricane Otto as it bee-lined for us from the Atlantic.  Luckily, it seems to have slowed considerably, and weakened into an extra-tropical depression on its way over.

Summary
We’re pleased to be doing work again, and I look forward to providing updates on the measurements as we continue south along the P18 section.  We have some concerns for our schedule and some work to do optimizing our CTD/rosette/winch setup.  However, it is refreshing to be facing these more-typical oceanographic hurdles instead of waiting on station 1.



Annie, Mike, Brian, Josh, and Sean, working together to deploy the APL/UW Gasfloat by crane over the Mexican ODZ.  Photo credit: Christian Lewis.

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